Lepidoptera

The Latin name of the detachment, Lepidoptera , comes from other Greek. λεπίς , genus n. λεπίδος (“scales”) and πτερόν (“wing”). The squad received this name due to the fact that the wings of its representatives are covered with scales, which are modified bristles.

The common Russian name for the representatives of this detachment - "butterfly" - dates back to Praslav. * babъka (< * baba ; "old woman, grandmother") and ideas about these insects as the souls of the dead ^{[5] [6]} . To this day, in many villages and villages they are called "granny", "grandmother", "grandmother", "grandmother", "grandmother".

The word "moth" goes back to praslav. * motyl (compare Czech motýl , Polish motyl - “butterfly”), which is derived from * mesti, * motati sę (“spin, jerk”) due to the nature of the flight of the insect ^{[7] [8]} .

The word "mole" comes from Praslav. * mol , which, according to one version, is derived from * melti ("grind", and then the etymological meaning of the word is "crushing (damaging) insect"), and according to another it is associated with other Greek. μῆλον ("small livestock"), ill. míl (“animal” - with the etymological meaning “small animal”) ^[9] .

The order of Lepidoptera in terms of species diversity undoubtedly stands out among taxa of a similar rank. Lepidoptera are one of the largest insect groups, including, as of August 2013, 158 570 species, including 147 fossil taxa ^[10] . It is expected that up to species are still unknown to science, and, therefore, the total number of creatures on the planet Lepidoptera species can be estimated at about ^{[11] [12]} species ^[13] . In Russia, there are 2166 genera and 8879 species from 91 families ^[14] . Of these, 7 families are found only in the Far East (where 1609 genera and 4871 species of butterflies were found in total) ^[15] .

Lepidoptera are characterized by great diversity, while most of their species are poorly understood. Some of the described species are known from finds from a single locality or even from a single specimen. A true estimate of the total number of existing species will never be known, because many species became extinct before they were discovered. The systematics of butterflies presented in various works reflects the various views of their authors and is, without a doubt, debatable. There are disputes about the systematic status or the need to maintain the status of certain subspecies or species. DNA studies suggest that some of the currently known species should be separated. A well-known example is the case when, at first glance, the identical Colias alfacariensis and Colias hyale , previously considered one species, were divided into two, after significant differences were found in the structure of their caterpillars and pupae.

The size of the representatives of the squad varies widely. The South American titania agrippina ( Thysania agrippina ) is probably the largest butterfly in the world in terms of wingspan. According to the literature, its wingspan can reach 28 cm ^[2] . The largest butterfly by day wing butterfly is Queen Alexandra's ornithopter ( Ornithoptera alexandrae ) - the female wingspan reaches 27.3 cm ^[2] . The largest day butterflies also include Papilio antimachus from Central Africa , the wingspan of males of which can reach 25 cm ^[11] . Females of Saturnia Coscinocera hercules , living in Australia and New Guinea , have the largest wing area ^[16] - up to 263 cm² ^[1] . One of the largest butterflies in the world is the peacock-eye Attacus atlas (wingspan up to 24 cm) and Attacus caesar (wingspan up to 25 cm ^[17] ) ^[18] .

One of the smallest known butterflies is the so-called baby moths of the family Nepticulidae : Stigmella ( Trifurcula ) ridiculosa ^{[1] [19]} , which lives on the Canary Islands and has a wingspan of 3.8-4.5 mm ^[20] , as well as common in northern Europe, Stigmella filipendulae with a wingspan of 3.25 to 5 mm and Enteucha acetosae with a wingspan of about 4 mm. The smallest species also include the Lycaenidae Micropsyche ariana from Afghanistan with a wingspan of about 7 mm; Brephidium exilis from the USA with a wingspan of 6-10 mm.

The largest day butterfly in Russia is the Maak ( Papilio maackii ), with a wingspan of up to 13.5 cm ^[11] . The largest night butterfly in Europe and Russia is the peacock-eye pear ( Saturnia pyri ), with a wingspan of up to 15 cm ^{[21] [22]} .

Building

Like all insects, the body of butterflies is divided into three main departments: head, chest and abdomen . Outside, it is protected by a solid chitinous cover forming the outer skeleton .

Head

The head is inactive, free, rounded in shape, with a flattened occipital surface. Cervical sclerites are well developed, triangular or L-shaped. The tentorium is P- or (in a number of primitive families, for example, Agathiphagidae ) Y-shaped, in primitive families (for example, Micropterigidae , Eriocraniidae ) also with well-defined dorsal processes.

Lepidoptera mouthparts are diverse. In a number of primitive families (for example, Micropterigidae , Heterobathmiidae ) - gnawing, with functioning mandibles and developed chewing lobes of maxillas . In species of the Glossata family, the sucking mouth apparatus — the proboscis — is formed by the strongly altered lower jaws, forming a tubule, which is spirally folded at rest. The proboscis consists of two semi-tubular parts, which touch the edges and are fastened by bristles coming into each other. The proboscis serves to feed liquid food. Inside it are small sensitive hairs that perform a receptor function.

Imagoes of a number of species have reduced oral organs (for example, clothes moth , peacock-eye and many others), do not feed at all, and live solely on the basis of nutrient reserves accumulated in the caterpillar stage ^[23] . The upper jaws of the representatives of the order are absent or are represented by small tubercles. The lower lip is reduced, forms a triangular or heart-shaped roller at the base of the proboscis from the lower side. Its palps are well developed and consist of three segments.

In the club-headed butterflies and moths , on the last segment of the palps there is a deep-lying fossa, in the lower part of which there are sensitive receptors in the form of cones. Its hole is located on the free end of the palp and is surrounded by a number of scales.

On the sides of the head are hemispherical, well-developed, complex, facet-type eyes, consisting of a large number (up to 27,000) ommatidia , giving a common mosaic image. The eyes are usually convex, round or oval, sometimes kidney-shaped. They occupy a significant part of the lateral region of the head and are surrounded by hairs diverging in a corolla. Sometimes the entire eye cuticle is covered with thin short hairs. Lepidoptera are able to distinguish colors, but to what extent - has not yet been studied enough. Some butterflies, such as urticaria ( Aglais urticae ) and cabbage ( Pieris brassicae ), distinguish red, while satyrs ( Satyrinae ) do not see it. Two colors most attract butterflies - blue-violet and yellow-red ^[24] . Butterflies also perceive the ultraviolet part of the spectrum , are sensitive to polarized light and are able to navigate it in space. Moving objects are distinguished much better than motionless ^{[11] [24]} .

In addition to the facet eyes, in Lepidoptera behind the antennae, 2 parietal simple eyes are often located on the crown ^[25] . The frontal eye is absent.

The antennae are located on the border between the crown of the head and forehead and are sensory organs that perceive odors and air vibrations. The antennae also help maintain balance during flight . According to the structure, bristle-shaped, filiform, club-shaped, hook-shaped, comb, cirrus tendrils are distinguished ^[23] . In males searching for females by pheromones ( peacock-eyes , bagpipes ), the antennae are highly branched and have a much larger surface than in females ^[11] .

Antennae have unequal length among representatives of different groups. In representatives of the family, long-whipped moths , especially in males, significantly exceed body length, and in thin-worms they are greatly shortened, slightly longer than the head; in wingless female mothbirds, they are almost completely reduced. The number of segments in the antennae usually reaches several tens. The first segment, or scapus, is larger than the rest.

Chest

The chest , as with all insects, consists of three segments : prothorax, mesothorax, and metothorax - bearing three pairs of legs and two pairs of wings. The prothorax is much smaller than the wing-bearing segments (mid- and posterior thorax), its tergite usually carries a pair of isolated plates (pathagia), the most developed, mainly in representatives of the scoop family.

Tegulae (movably articulated plates at the base of the wings) of the mesothorax are strongly developed, covered with scales, almost completely cover the bases of the fore wings and are clearly visible, unlike most insect orders ^[23] .

The structure of the legs of most butterflies is typical for insects; they are walking or running. The coxae are large, their connection with the chest is inactive, the free part of the leg includes the trochanter , thigh , lower leg and tarsus (in most species, all tarsi are five-segmented with a pair of claws at the end). The specific features of the detachment include the characteristic formula of spurs (1-2-4) - spikes movably articulated with lower legs. In the middle of the front tibia, as a rule, there is one spur - the so-called pineal gland, used to clean the antennae. The middle tibia carries one pair of spurs at its apex, and the hind tibia are two pairs that are located in the middle and on top of the tibia. In some groups of butterflies, some of the spurs are reduced. In representatives of few groups, the legs undergo a more or less significant reduction: in the males of the thin- worm Hepiolopsis hecta, the hind legs are reduced, and the hind tibia are spade-shaped and bear odorous scales. The legs of females of some mussel moths ( Psychidae ) are almost completely reduced. In some day butterflies, the front legs are reduced to one degree or another, in lycaenidae - less significantly, in nymphalids - until their walking ability is completely lost, as a result of which these butterflies move on four legs (middle and hind). In most species, taste buds , modified sensilla, are located on the paws ^[24] .

Wings

The wings are two pairs, webbed, with a small number of transverse veins. Venation of wings plays an important role in the taxonomy of butterflies at various levels - from species to suborder . Previously, many entomologists shared all Lepidoptera on Homoneura (with approximately the same shape and venation of the front and rear wings) and Heteroneura (with a reduced number of radial veins on the hind wing and often - significantly different in size and shape of the front and hind wings). These names are still preserved to indicate non-taxonomic groups within the order .

In males, the wings are always fully developed; in females of representatives of a number of families — leafworms ( Tortricidae ), Oecophoridae , bagpipes ( Lymantriidae ), dipper ( Arctiidae ), moths ( Geometridae ) - there are isolated cases of partial or complete reduction , and in the burdock family ( Psychidae ) wingless females of most species ^[23] . In Pterophoridae, the wings are split into linear, cirrus lobes.

By the participation of the wings and their muscles during the flight, lepidopterans are classified as bimotor and anteromotor ^[26] . Bimotorism means equally the development of both pairs of wings and their movement of muscles. Front-engine represents the union and friendliness in the work of the front and rear wings. In the course of such a union, functional two-wingedness arises - both pairs of wings function as one. Moreover, during flight, the main load falls on the front pair of wings, which sometimes leads to weakening of the rear pair ^[26] .

The hitching device of the wings in the lower groups is formed by a protrusion at the rear at the base of the front wing, which protrudes above the front edge of the hind wing ^[23] . In higher groups of butterflies, the same effect is achieved with the help of bristles or a bundle of bristles located at the front edge of the hind wing ^[23] . Most species of maceous butterflies are devoid of such “attachment”, and the fastening edge of the hind wings, on which the edge of the upper wings comes in, contributes to the fastening of the wings ^{[23] [26]} .

In representatives of the suborder of different- winged butterflies, the anterior pair of wings acquires more importance during the flight , and the posterior pair often decreases in size and loses part of the veins. Accordingly, there is an increase in the middle chest segment and its muscles, while the hind thoracic segment is weakened.

Wings, as a rule, are completely covered with scales, which are modified bristles ^{[11] [23] [27]} . The scales have a diverse shape, but are most often flat. At their base is a short stalk with which the flake is attached in the recess of the wing, called the sac of the flake ^[28] . At the end of the stalk there is an extension that enters the inside of the sac. Often in the stalk part of the scale there are recesses (sinuses), which are found exclusively in the maceous butterflies , while the dissimilar scales are whole-cut ^[28] . However, the scales on the underside of the wings of the club-butterfly butterflies are also whole-edge ^[28] .

Narrow hairy scales are usually located along the edge of the butterfly wing, often with branched apices, forming the so-called fringe, in the middle of the wing are wider ^[11] . The fine structure of flakes plays an important role in the macroscopic system of Lepidoptera ^[28] .

The scales are located not only on the wings, but also on the body of the butterfly ^[28] . So, for maceous butterflies, the scales on the chest are small, irregular in shape, with a pointed edge. Pectoral scales of other groups are larger, of the same shape and size. Scales covering legs, longitudinal and small. Often flakes have a longitudinal rib caused by protruding chitinous trihedral tubules ^[28] .

Abdomen

Lepidoptera abdomen usually consists of 9-10 segments, I of which is partially reduced, its sternum is merged with the sternum of segment II ^[19] . The remaining segments are distinguished by the simplicity and constancy of the structure, forming sclerotized rings, interrupted on the sides by membranous sites - pleurites and equipped with spiracles up to segment VII inclusive. The abdomen is elongated, cylindrical in shape, and in males it is thinner and sometimes somewhat flattened laterally. Tergites and sternites are approximately equal in size, spiracles are located on membranous pleura. The abdomen, like other insects, includes ten segments, with segments I and II usually more or less reduced, and the X segment often merges without a trace with IX. The VIII segment in females is elongated, forming part of the ovipositor, and in males it is modified in connection with the functioning of the copulative apparatus. Typically, the IX — X segments of males carry copulative appendages, and the VIII — X segments of females are transformed to some degree or another by developed telescopic ovipositor . The male genitals in a calm state are pulled into the VIII segment of the abdomen (exception: Micropterigidae ) ^[19] and extend out only before copulation. Their skeletal basis is the IX segment, which in archaic forms is a solid sclerotized ring - the annulus ( annulus ). In more developed taxa, the IX segment is usually divided into the dorsal part - tegumen, and ventral - vinculum. Their structural features are sometimes used to diagnose families, subfamilies, and tribes ^[19] .

A number of families (for example, scoops , moths , many fireflies ) have a peculiar organ of hearing - the so-called tympanal apparatus ^[19] , which are the deepened membranes of the posterior thorax, or the first two segments of the abdomen equipped with mechanoreceptors . Sound vibrations propagating in the air cause the membrane to vibrate , which causes excitation of the corresponding nerve centers ^{[29] [30]} . These organs are able to perceive ultrasonic vibrations from 10 to 100 kHz ^[30] .

Internal organs

The internal structure of Lepidoptera as a whole is typical of insects , with the exception of several characteristic features. In the digestive tract of the imago, the esophagus is enlarged, forming a goiter , the muscular stomach is reduced. The only enzyme secreted by the digestive system of the imago of some Lepidoptera is invertase ^[28] .

Male reproductive organs consist of two lobed testes , which are enclosed in one common, brightly colored sac, of two testicles , locally forming extensions ( seminal vesicles ) and connected into one common ejaculatory canal, which opens at the base of the evertible endofallus or vesica enclosed inside the sclerotized copulative organ.

Female reproductive organs consist of two ovaries with 4–5 (in primitive species, the 20th ^[31] ) egg tubes in each, paired oviducts, uniting into a common oviduct, opening outwards by an ovary opening. Ditrysia , the majority of the butterflies, also has a separate copulative opening leading to the copulative sac, the duct of which connects to the common oviduct at the confluence of the seminal receptor ( spermathecus ) and adnexa. In Exoporia ( Hepialidae ), the copulative and ovary openings are also isolated, but connected by a groove on the abdominal surface of the body. Finally, in monotrice Lepidoptera, the copulative opening is connected to the ovary.

The structure of the copulative apparatus in each species has its own characteristic features, and in some cases, close forms, which are very different in appearance, can be recognized precisely by the copulative organs of males.

Pigments and coloring

The appearance and color of butterfly wings have an important role in improving their survival. This is a protective camouflage , intraspecific sexual recognition during mating, andaposematic demonstration . The color of the lepidopteran wings can be pigmented (depends on the pigments contained), optical (depends on the refraction of light ) and combination (combining the two previous types of coloring). The bright coloration of the wings of some butterflies (for example, such large and spectacularly colored butterflies as Ornithoptera ) is controlled by two main mechanisms: diffuse reflection of incident light from multilayers and spectral filtering of the inner pigment ^[32] .

Each pigment flake contains only one pigment. Most often it is melanin , which gives black and brown colors, and carotenoid lipochromes , which are characterized by photosensitivity and cause yellow-green, yellow, brown, orange and red color ^{[11] [28]} . Flavonoids provide the color of yellow, white, red and brown colors ^[27] . In whites, the yellow color is due to the pigment xanthoperin and purine bases formed from accumulated uric acid ^[11] .

Two types of pigments are distinguished - diffuse and granular. The former stain chitin , but in scales the pigments are contained in the relief, and the chitin plate is often lacking pigment or slightly colored. Granular pigments are present only in representatives of the family of whitefish ( Pieridae ) and are immersed in the chitinous shell of flakes ^{[27] [28]} .

The location of variously colored scales on the wing is regular and forms complex patterns characteristic of each species, and often of a systematic group.

With optical coloration, thin-layer interference occurs in the flakes of the wings. The pigment at the bottom of these flakes does not transmit light and gives greater brightness to the interference color. Rays of light passing through the scales are reflected both from their external and internal surfaces, and as a result, two reflections overlap and reinforce each other ^[11] . Two types of butterfly scales with a metallic color can be distinguished: with wrinkled plates of scales and oblique parallel grooves ( morphids ); and with a much thicker upper plate, which is relatively flat ( uranium ).

Lepidoptera with optical coloring of the wings - morphids , uraniums and partly sailfish , some species of nymphalids , lycaenidae , whites and some others.

The satyrs of the genus Cithaerias from South America are peculiar, the wings of which, having lost their scales, became transparent, and only on the hind wings the "eyes" typical of satyrs are preserved. Partially transparent wings also have some types of heliconids , glass- boxes , and hawks ^[27] .

In almost all butterflies, the pattern on the left pair of wings is identical to the pattern of the right, being a mirror image, but there is an exception - Madagascar uranium ( Chrysiridia madagascariensis ) with an asymmetric pattern on the wings.

Polymorphism and other forms of color variation

In some hot and dry years, a connection is found between weather conditions and changes in the appearance of butterflies: the appearance of butterflies with signs of southern climatic forms. The change of seasons causes seasonal dimorphism and trimorphism in many species. Among day butterflies, one can also find several examples of polymorphism - the simultaneous and coexistence of differently colored forms in one form, freely interbreeding and transmitting their signs to offspring (for example, jaundice , large mother of pearl and others).

Polymorphism

One type of variability is the case of polymorphism, when among individuals of the same species in the same locality and at the same time there are several different forms that differ sharply from each other in appearance, not connected by transitions, although these forms may cross freely among themselves ^[33] . Polymorphism is the appearance of various forms that differ in color and a number of characters within one species. For example, in individuals of the Kaya bear ( Arctia caja ), developing under the same conditions, sometimes color variability is observed, and sometimes these differences are so large that butterflies can be mistaken for representatives of various species ^[28] .

Among European species, an example of polymorphism is the large forest mother of pearl ( Argynnis paphia ), in which the males are the same color, but the females come in two forms. Along with ordinary red females, there is a dark form of valesina , in which the general background of the wings is greenish-gray ^[33] . If the differences between the various forms of males or females are limited by the color of the coloration, without affecting other characters, then such special cases of polymorphism are reduced to dichroism (two-color) or polychroism (multi-color) of individuals of each sex; thus, for example, the dichroism of females takes place in the large forest nacrement mentioned above ^[33] .

Seasonal polymorphism

Differences in external conditions acting on the pupa are somehow reflected in the signs of the butterfly itself. Under the influence of the temperature effect on the pupa, many species show changes in the color and pattern of the wings, and sometimes even in the form of wings. Such variability is expressed in the form of the so-called seasonal dimorphism, when different generations of the same species, developing in different months of the year under different weather conditions, differ externally in some way ^[33] . This phenomenon is also called seasonal polyphenism .

An example of seasonal variability is the varnifold ( Araschnia levana ). The spring generation has wings of reddish-red color, with a pattern of black spots, with white spots at the apex of the fore wing; in the summer generation, the color of the wings is black with white spots. Color change in different seasons is associated not only with the temperature regime, but also with the state of the pupa. The amount of pigment in the wings of a butterfly depends on the content of the hormone 20-hydroxyecdysone in the pupa — less is produced in spring and more ^{[28] [34]} . Many tropical butterflies also have seasonal forms called wet and dry seasons.

Seasonal polymorphism can also be observed in a less pronounced form in a number of other species: Leptosla sinapis , Chrysophanus phlaeas , Chrysophanus dorilis , Everes argiades , Cyaniris argiolus, and many others ^[33] .

Phenomena of seasonal polymorphism are not always associated with the effect of low temperatures on the pupa of the spring generation. Many tropical lepidopteran species have a rainy season and a dry season.

Temperature forms and aberrations

Some species of temperate latitudes also have seasonal differences in the appearance of butterflies of various generations, although not one of them was exposed to low temperatures during the pupal stage. Such are meadow yaundice , Icarus lycaenidae , large brown-eye , pearl semen , and some others ^[33] . In such cases, seasonal differences between butterflies of different generations may depend on the difference in the living conditions of the caterpillars, partly on the uneven ambient temperature, to which pupae are exposed during different months of the summer season.

Temperature effects on the chrysalis cause changes in the appearance of a number of species, for example, hives , mines , multicolor , multicolor black-red, and others, called “temperature forms” ^[33] .

When exposed to elevated temperature, the butterfly emerging from the chrysalis will have a color characteristic of southern forms, and at lower temperature forms with a northern type of color appear ^[35] . So, at the mourn , under the influence of low temperatures on its pupa, the general background darkens, and blue spots on the wings decrease. The red color on the wings can be replaced by black (the Bear Hera ), yellow - on red (the Bear Madam ) ^[28] .

Aberrations are called inconstant, randomly occurring changes in the appearance of a butterfly, appearing under the influence of various, mainly temperature, factors on the pupa. Most often, aberrations are manifested by the appearance of atypical coloring of the wings. The aberrations are also customary to attribute the appearance of individuals with different sizes of the wings of the same name, when one wing is larger than the other.

Geographical polymorphism

Different populations in different parts of their range differ from each other in certain signs. An example is the coloration of various subspecies of Ornithoptera priamus , living in the Moluccas and Solomon Islands , in New Guinea . So the males of the poseidon subspecies have a bright green color of the wings, the demophaneus subspecies have a yellow-green color, the urvillianus subspecies have a bright blue color, and the miokensis subspecies have wings from blue to aquamarine ^[27] .

An even more famous example of geographical polymorphism is the representatives of the genus Apollos ( Parnassius ), including the common Apollon , the location and size of the spots on the wings of which varies greatly, forming more than 600 known forms ^[36] . Apollo form local populations that do not have contacts between each other, and due to the strong stenotopic nature of the species and weak migration ability, the cross between populations of the same species practically does not occur. In almost every isolated area, the pattern on the wings of the same Apollo species is slightly different ^[36] .

Albinism, Melanism, Nigrism

The color can sometimes change due to the absence of pigments - albinism , or vice versa to change from a brighter pigment, or an excess of dark - melanism ^{[27] [37]} . The appearance of albinism and melanism is much more common in representatives of dissipated lepidoptera.

Wings and other parts of the body can be evenly pale. Sometimes not all the scales turn pale, and among them remain small groups with a normal color, evenly scattered on the wing surface. Such specimens are sometimes found among different species of Satyridae , Epinephete jurtitta, and Epinephete tycoon ^[33] . In other individuals, whitened areas can be distributed asymmetrically along the wing. There is also such a form of albinism, when only those parts of the wing that are normal in one specific color (for example, the red background of the wings of some mother-of-pearl ) are whitened , while all other parts of the pattern retain their usual color ^[33] .

Lepidoptera albinism is invariably associated with the underdevelopment of the flakes themselves, which acquire an ugly shape ^[33] .

Excessive coloring of the wings and body with black pigments is observed much less often than albinism. In melanism, the usual black pattern of a butterfly remains normal, but at the same time, the general background of the wings is more or less darkened, sometimes so much so that the whole butterfly appears uniformly black (various species of whites , Synchloe uaptidice ) ^[33] .

The phenomena of nigrism should be distinguished from real melanism, when the black pattern on the wings is changed - black stripes and spots increase relative to their size, blur or stretch and merge with each other. Examples include female cabbage , in which two black spots are connected by a jumper ( ab. Nigronotata ), specimens of lycaenidae , with round spots on the underside of the wings in the form of an exclamation mark or merged into longitudinal strips, etc. ^[33] More sharp and spectacular examples of nigrism can be found among mother of pearl ( Argynnis ) and draftsmen . In extreme cases, the usual pattern of the butterfly can be changed so much that only a few spots remain along the edge of the wing from the red background of the wings.

Changes in the direction of nigrism usually occur under the influence of external conditions - mainly temperature ^[33] , so these changes must be attributed to the number of aberrations.

Sexual Dimorphism

Sexual dimorphism - differences in the appearance, color and / or body shape of the male and female - is widespread and sometimes pronounced among various lepidopterans. In addition to differences in the structure of the antennae, females of many Lepidoptera, as a rule, are larger than males, with a large abdomen; have a less bright color, sometimes completely different from that of males. In most cases, these differences are caused by reproductive oviparous function and less female mobility. The most severe manifestation of sexual dimorphism is the partial or complete loss of the wings by the females ( scapulata , some moths and bagpipes ), as well as the legs and antennae. Such winglessness of females is associated with climatic conditions and is typical of highland and arctic species, as well as flying in early spring or late fall. For example, a female Lachana selenophora, Pamir and Tien Shan, with completely reduced wings, has almost no legs and has a large barrel-shaped abdomen for egg production ^[38] .

In butterflies of the genus Ornithoptera, males are smaller than females and have brightly colored wings, females are much larger and painted in brown-black tones. The males of many morphids ( Morpho ) have a bright blue color, while the females are yellow-brown.

One of the manifestations of sexual dimorphism is the difference in the color of the wings, visible only in ultraviolet radiation ^[28] .

Industrial melanism

Industrial melanism is an increase in the frequency of dark-colored forms associated with the intensive development of industry ^{[39] [40]} . Near areas with large industrial centers in Europe (especially England ) and in North America, dozens of species have been described, in the populations of which melanistic forms were found.

The most famous example of this phenomenon is the birch moth ( Biston betularia ). Until the mid-19th century, all specimens of the birch moth collected by entomologists had white-grayish coloring of wings with dark spots ( morpha typica ), which provided a protective color on tree trunks. Now many populations are polymorphic, they contain black melanistic forms - Biston betularia morpha carbonaria ^[39] .

The increase in the frequency of melanistic forms is a consequence of directional selection, the main driving factor of which is the selective eating of butterflies by birds ^[41] . In the forests around industrial conglomerates and cities, tree trunks are often deprived of lichens and may be blackened with soot. In such areas, the protective color is black, and in unpolluted areas a light spotty color ^[39] .

Also known is the third form, which is intermediate in darkness in color between the melanistic and light forms of the birch moth - morpha insularia . This type of coloring, like melanistic , dominates over light, but, apparently, is determined not by one but several loci.

Based on laboratory experiments, it was assumed that the alleles that control the melanistic color have a pleiotropic effect , determining not only the color of the butterfly, but also its behavior (choice of background) ^[40] . However, this was not confirmed by observations in nature.

Flight

The main form of Lepidoptera movement is flight, both active (waving) and passive (soaring, planning, diving) ^[26] .

The actions of the butterfly wings during active flapping flight are a sequence of certain movements that form a closed cycle. Each cycle consists of a flap of the wings, which were in an extremely upper position, down, not lower than the body, and a return flap of the wings up. When the wings are flown down, the butterfly acquires a certain impulse to move upward, pushing off from the air.

The ability to soar flight is possessed by representatives of the families: Danaids , Nymphalidae , Papilionidae , Pieridae , Morphinae , Uraniidae . Small species from the nymphalide family use the thermal fluxes that form near the ground for soaring; larger species soar much higher, often at the level of tree crowns ^[26] . Representatives of the sailing family are even more adapted to soaring, especially the Parnassius , which can soar over mountain slopes for a long time, adjusting the flight path with a wave of wings and changing altitude ^{[11] [26]} .

Increased stability during a soaring flight is achieved due to the long tail-shaped outgrowths of the hind wings.

Such outgrowths are especially long in butterflies of the Saturnian family — for example, Actias artemis , Argema mittrei , Coscinocera hercules , and Argema mimosae ^[26] .

All species capable of steaming also use planning, which is often resorted to by nymphalids , sailboats , danaids, and other lepidoptera ^[26] . A characteristic sign of adaptation to the latter is the elongation of the tops of the front wings. Planning flight is also characteristic of Lepidoptera with a large wing area. Having dispersed, they stop the movement of their wings, and for some time they plan due to inertia ^[26] .

Diving as a kind of passive flight is observed in Callimorpha and the scoop from the Leucanilis group living in the grass. The wings of the butterfly with such a dive are slightly laid back, which helps to achieve high speed ^[26] .

The flight of the representatives of the Heterocera group differs markedly from the flight of the maceous butterflies, this is primarily due to the angle of the arc described by the wing - in maceous butterflies it reaches 140–150 °, and in heterous butterflies it reaches 80–90 ° ^[11] .

For the flight of most species, the optimum body temperature is between 30–35 ° C ^[16] . Night species before flight intensely vibrate with their wings, thus increasing body temperature ^[16] .

The most perfect flight among representatives of the family of brazhniki - having a fast maneuverable flight, they are able to hang in the air, fly vertically up and down, and also back, like a hummingbird . Most butterflies can reach a speed of 8-17 km / h ^[11] .

Nutrition

Most species, being anthophiles , feed on flower nectar . Many Lepidoptera also feed on tree sap, rotting and overripe fruits . Brazhnik dead head eagerly eats honey from nests and beehives. Primary tooth moths feed on pollen .

Species with reduced oral organs do not feed and live solely due to the reserves of nutrients accumulated in the caterpillar stage.

A number of species from the families of nymphalids , sailboats, and others require microelements , primarily sodium , for their vital functions ^[11] . They willingly fly on wet mineral clay , on excrement and urine of large animals, moist charcoal , human sweat - from where they get moisture and necessary trace elements ^[42] . Often males of these species gather in groups on wet sand and clay soils, along the banks of streams, near puddles ^{[11] [16] [27]} .

Among the butterflies, as an exception, there are predators ^[43] , which are the scoops of the genus Calyptra : for example, Calyptra eustrigata , which inhabits the territory from India to Malaysia , Calyptra thalictri and Calyptra lata . Males feed on tear fluid ( lacrifagia ) and the blood of large animals, piercing their integument with an acute proboscis ^[43] . Females feed on the juice of fruits and plants ^[27] . The scoop Hemiceratoides hieroglyphica , drinking bird tears, has developed a specialized proboscis with a harpoon-shaped tip ^[44] .

Thermoregulation

Lepidoptera, like all insects, are traditionally regarded as poikilothermic organisms (whose body temperature depends on the ambient temperature), in contrast to warm-blooded organisms (which maintain a stable internal body temperature, regardless of external influences). However, the term “thermoregulation” is currently used to describe the ability of insects to maintain a stable temperature (above or below ambient temperature) in at least some part of their body, by physiological or behavioral means ^[45] .

Many lepidopterans are ectotherms (animals for which the environment is a source of heat), while others can be endotherms (independently produce heat inside their body). Endothermic insects are more correctly described as heterotherms, because they are not entirely endothermic. For example, butterfly species that are active at night produce the heat necessary for their flight by contracting the chest muscles, but their abdomen practically does not heat up ^[46] .

Genetics

Sex Determination

Apparently, the mechanism of sex determination for butterflies was the mechanism Z0 female / ZZ male ^[47] . Then, through chromosomal rearrangements, a sex determination system WZ female / ZZ male, characteristic of 98% of butterfly species, arose. In species with the Z0 / ZZ system, sex determination depends on the ratio of the number of pairs of sex chromosomes and autosomes, but in the mulberry silkworm (WZ / ZZ system), the Fem gene responsible for female development in the W chromosome was found .

Ginandromorphism

During the development of the butterfly, genetic changes are possible, leading to the appearance of ginandromorphic butterflies - half-males, half-females, in which one side of the body is completely male and the other female (the so-called bilateral gynandromorphs).

Sometimes only small areas of the butterfly’s body become abnormal, then they talk about mosaic ginandromorphism. So, in different parts of the wing, the male may have areas of female color and vice versa. Typically, such individuals are not viable, but while maintaining the functionality of the internal organs of the imago are viable.

In Lepidoptera, the basis for the appearance of gynandromorph is usually the formation of binuclear oocytes , in which one of the nuclei is formed, for example, from the nucleus of the polar body . If one of these nuclei contains a Z-chromosome, and the other contains a W-chromosome , then, when fertilized by two sperm , fission of these nuclei may result in descendant cells of the male and female halves of the body. The second possible reason is the loss by the nucleus of the embryo of one of the Z chromosomes in the first stages of fragmentation (usually during the first division of the zygote ) ^{[27] [37]} . During the development of the embryo from the descendants of this nucleus, the development of cells of the female half of the body will occur; this variant has been described in moths of the genus Abraxas ^[48] .

The incidence of ginandromorphs is approximately one case at 90 000 ^[27] . For their rarity, they are highly appreciated by collectors.

Intersexuality

Usually, insect cell development is genetically autonomous, and sex hormones do not affect secondary sexual characteristics. Therefore, butterflies are characterized by genetically determined intersexuality resulting from a deviation from the norm of the ratio of the number of sex chromosomes and autosomes (triploid intersexuality) or imbalance of genes (diploid intersexuality) ^[47] . Diploid intersexuality was described by R. Goldschmidt in unpaired silkworms ( Lymantria dispar ) when crossing different geographical races, although later his data were called into question ^[49] .

Usually, the Wolbachia bacterium causes cytoplasmic incompatibility or sex change in butterflies (the transformation of genetic males into functional females); under certain conditions, in the Eurema hecabe and Ostrinia scapulalis moths, its effect can lead to the appearance of true intersexes ^{[50] [51]} .

In Morpho aega , cases of the appearance of female forms with blue wing coloration, characteristic of males of this species, are known. The blue color of such females is due to the fact that the shape of the scales on their wings is the same as that of males; perhaps these females are intersex ^[27] .

Interspecific Crossing

Interspecific crossing - crossing individuals of various species. In Lepidoptera, cases of interspecific crossing in closely related species of sailfish , peacock-eye , and nymphalids are known. Lepidoptera hybrids can be intraspecific (when crossing different subspecies), intrageneric (when crossing species belonging to the same genus). As a rule, interspecific hybrids are not capable of reproduction ^[28] . A number of butterfly hybrids are specially artificially bred by human cultivation for commercial purposes in view of their great popularity and high cost among insect collectors, for example, the Graellsia isabellae x Actias dubernardi hybrids, Graellsia isabellae x Actias luna , as well as all kinds of interspecific ornithopter hybrids. The emergence of many such hybrids in natural conditions is impossible due to the geographical or seasonal isolation of species.

Coloring Genetics

In recent years, the study of the genes responsible for the winged pattern of Lepidoptera has attracted much attention of geneticists ^[52] .

Reproduction

In the biology of breeding butterflies, the coloring and shape of the wings (attracting partners), as well as complex forms of courtship (mating flights and dances) play an important role. Some species are characterized by sexual dimorphism , which plays an important role in the normal course of the sexual cycle, since external differences facilitate the identification and finding of a mating partner of their species ^[53] .

Pheromones produced by male club-moths and females of nocturnal species contribute to the search for partners of each other. Many males of maceous butterflies have odorous scales - androconia , which are located on the wings, less often - on the legs ^[11] . In whiteflies, androconia are located almost over the entire surface of the wings ^[33] . In other species, they are concentrated on certain parts of the body, and often form special velvety spots or stripes on the wings ^[33] .

The organs secreting pheromones in females are located on the posterior end of the abdomen between segments 8 and 9, and in a number of species they can move out. Saturn males can find a female by pheromones at a distance of several kilometers ^{[11] [54]} .

Lepidoptera can have complex forms of courtship - mating flights and dances. Some, for example, tails arrange mating flights - males fly under the female, and then turn in the opposite direction, touching the wings of the female’s antennae; in lemongrass , the female flies ahead, and the male follows her, keeping a constant distance ^[16] . In other species, the female can sit on the plant, and the male makes a “dancing” flight directly above her, secreting pheromones that stimulate her to mate ^[16] .

Mating takes place on the ground or plant and lasts from 20 minutes to several hours; all this time the mating individuals remain motionless. During mating, the female receives from the male not only sperm, but also a number of some proteins and trace elements necessary for the formation and laying of eggs ^[16] .

After mating, female sailboats carry a hard chitinous appendage on the underside of the abdomen - sphragis ( Latin sphragis - seal, seal), formed by the male during mating. Most often, sphragises are found in Parnassius , as well as related species. The purpose of sphragis is the exclusion of repeated fertilization of the female by other males.

Parthenogenesis is extremely rare in butterflies; it is observed in mothbirds ( Psychidae ), moths of the genus Solenobia , and as an exception, in some silkworms ( silkworm ) ^[28] .

Heliconide charitonia ( Heliconius charithonia ) is distinguished by the peculiarities of the reproduction process. A few hours before hatching from the pupa, females secrete pheromones , attracting males who vie for the right to mate with the female. Usually, the largest male wins in such rivalry, and when the female exits the pupa, she immediately begins to mate with her. This phenomenon in the English-language literature has received the name "pupal rape" ( English pupal rape ) ^[55] .

Most butterflies in the temperate zone of North America and Europe produce one or two to three generations a year. In the tropics can be up to 8 - 10 or more generations over the same period of time. For example, the life cycle of Hypolimnas misippus takes only 23 days.

Life Cycle

Butterflies are insects with a complete transformation , or holometamorphosis. Their life cycle includes four phases:

• an egg
• larva ( caterpillar ),
• doll
• adult insect ( imago ).

Egg

Butterfly eggs are covered with a dense hard shell and can be of various shapes. Depending on the genus and type, the eggs can be round, cylindrical, spherical, egg-shaped, angular. Their outer surface can be embossed, forming depressions, points, stripes, tubercles, located, as a rule, in a symmetrical order. The color is most often white and greenish, less often brown, yellow, red, blue, dark green, sometimes with a color pattern ^[28] .

Females lay eggs on leaves, stems or branches of fodder plants. Their number in the clutch depends on the species and can be more than 1000 ^{[25] [28]} , however, few survive to the adult stage. Depending on the species, eggs can be laid individually or in groups of 10 or more ^[25] . Females can cover their eggs with hairs from a thick bundle at the end of the abdomen. The laid eggs can also be covered with secretions of the accessory genital glands, which, solidifying, form a protective shield ( apple moth ).

Epicopeia females ( Epicopeia mencia ) are remarkable for their amazing attachment to places that were once chosen for laying eggs, which have remained unchanged for many years and, as a rule, are represented by the same elm trees. Such selectivity leads to the fact that the majority of egg-laying places concentrate on the few that are especially attractive for butterflies and fodder trees ^[56] .

The average duration of an egg stage is 8–15 days ^[28] . In many species of the temperate zone, eggs laid in the fall in winter are in a diapause state ^[28] .

Caterpillar

The caterpillar is a butterfly larva. It is usually worm-shaped, with a gnawing mouth apparatus. The physiological feature of the caterpillars is the presence of a pair of altered salivary glands that open with a common channel on the lower lip and produce a special secret that quickly hardens in the air, forming a silk thread.

Most caterpillars are phytophages - they feed on leaves, flowers, and fruits of various plants ^{[4] [57]} . All herbivorous caterpillars can be divided into three categories: polyphages, oligophages and monophages. Caterpillars of some species - keratophages - feed on wax , wool , and horny substances (caterpillars of moths of the genus Ceratophaga live in the horns of African antelopes , feeding on keratin ). Few species ( glass and woodworms ) are xylophages and feed on wood , gnaw passages in the trunks and branches of woody plants or the roots of herbaceous plants ^{[58] [59]} . Caterpillars of some species are predators, feed on aphids , worms , larvae and pupae of ants ^[4] . For example, the caterpillars of the moths of the genus Eupithecia , which live in the Hawaiian islands , are insectivorous and have a whole arsenal of devices for catching prey.

Caterpillars of some species are characterized by oligophagy - feeding a very limited number of plant species. For example, polyxena caterpillars feed on only four species of plants of the genus Kirkazon .

Caterpillars distinguish three main groups of digestive enzymes - proteases , carbohydrases and lipases ^[4] .

The body of the caterpillar consists of 3 thoracic and 10 abdominal segments. The skin is smooth, with rare warts, setae or hairs, spikes. The thoracic segments carry 3 pairs of articulated legs, the abdominal segments usually have 5 pairs of thicker legs, with hooks on the soles to help the caterpillar stay on the substrate. Moths and some scoops have a decrease in the number of abdominal legs to 2-3 pairs, or they are reduced ^[4] .

Most of the caterpillars lead a terrestrial life, but the caterpillars of a number of species of the family wide-winged fireflies ( Pyraustidae ) live underwater, and adult wingless females live in the underwater firebrand Acentria ephemerella .

By way of life, caterpillars are conditionally divided into two large groups ^[4] :

• caterpillars, leading a free lifestyle, openly eating on fodder plants;
• caterpillars leading a hidden lifestyle.

Caterpillars, leading a hidden lifestyle, live in portable cases, which they build from a silky thread ( scabbard , Psychidae ), or from pieces of leaves (a series of fires ) ^{[23] [60]} . Caterpillars drag such a case on themselves, hiding in it in danger. Other caterpillars build shelters from leaves, folding and fastening them with a silky thread, often forming a cigar-shaped tube. The caterpillars living inside various parts of plants also lead a hidden lifestyle. This includes butterflies from the groups: moth miners ( Tischeriidae ), moths ( Laspeyresiini ), as well as gall-forming species.

The body color of the caterpillars is interconnected with their lifestyle. Caterpillars, leading an open lifestyle, have a protective color, combined with a certain body shape, sometimes resembling parts of plants ^[4] . Along with patronizing coloring, a bright demonstration coloring is common, indicating their inedibility. Some caterpillars at a time of danger take a threatening pose, for example, a large harpy , a wine middle hawthorn ^[61] .

Caterpillars of butterflies living in the northern latitudes sometimes do not have time to complete their life cycle in one summer, because of which they are forced to fall into winter diapause until next summer. The burrowpiper Gynaephora groenlandica inhabiting the Arctic Circle in Greenland and Canada is known for the fact that the life cycle of its caterpillar can last up to 14 years ^[62] . Typically, the life cycle is up to 7 years ^[62] . The second unique opportunity of caterpillars of this species is that during wintering in the diapause stage, they can survive a temperature of −60 ... −70 ° C ^[62] . When the ambient temperature decreases at the end of the Arctic summer, the caterpillars begin to synthesize chemical compounds protecting from the cold, such as glycerin and betaine ^[62] . Caterpillars spend about 90% of their lives frozen in a state of diapause, and only about 5% feed on sparse vegetation. The life cycle of the caterpillars of its sister species, Kuznetsova , the endemic of Wrangel Island , lasts up to 6 years ^[63] .

Doll

Butterfly doll inactive; in primitive Lepidoptera, forming taxa Protolepidoptera and Palaeolepidoptera , pupae are of the toothy type ( pupa dectica ); in the vast majority of Lepidoptera, forming the Neolepidoptera taxon, pupae are glued ( pupa conglutinata ) ^[64] . In families such as Saturnia and cocoonworms , the pupa is located inside a special cocoon woven by the caterpillar.

Pupa shape from elongated cylindrical, ovoid to almost round. The color is mainly patronizing, plain from light to dark or with a different pattern of dots, spots and stripes. Immediately after pupation, the color is often pale, sometimes almost white or greenish, then it changes to the characteristic of this species, and the pupa turns, for example, from green to brown ^[65] .

The outlines of the rudiments of the wings, proboscis and legs, abdomen with spiracles on the sides, and the cremaster at the end of the abdomen are a special thickening, often bifurcated at the apex, with hooks for fastening with spider webs to the substrate ^[65] .

Sometimes it is located openly on the plant, but more often it is inside braided folded and glued leaves, or in the surface layer of soil, on the stems and trunks of plants.

The pupa is more often attached to the substrate (hanging pupae and girdles are distinguished) ^[65] ; less often, it lies freely on the litter or the ground among plant debris in a rare web. The hanging chrysalis is attached with the head end down with the help of a cremaster, belted - with the head up, except for the cremaster it is supported in this position by a special cobweb belt ^[65] .

Pupae do not feed. In some species, the pupa is a stage that falls into the winter diapause .

Imago

An adult insect, an adult, emerges from the pupa. About a day before the butterfly leaves, the pupal shell becomes oily transparent. Then the pupa ruptures along the head and front edge of the wings, and the imago, clinging with its feet to the edge of the torn shell, creeps out. In many lepidopteran groups, males emerge from pupae earlier than females; therefore, at the beginning of the flight period of moths, only males are found, and at the end, only females ^[16] .

In the first minutes after exiting the chrysalis, the butterfly is not yet able to fly. It climbs to vertical elevations, where it remains until the wings spread, which occurs under the influence of hydrostatic pressure of the hemolymph ^[66] . Spread wings harden and acquire their final color.

Many groups and species have a difference in the timing of the appearance of males and females, which is up to 10 days. Such a delay in the start of flight of females is due to a higher rate of preimaginal development of males ^[67] .

The imago is a sexually mature form capable of breeding . The main function of this stage of the life cycle is reproduction and resettlement. The life expectancy of adults ranges from several hours to several months (in species falling into diapause ) and averages 2-3 weeks ^[28] .