Furthermore, in recent years students of insect metamorphosis have paid close attention to the role of hormones in controlling the life of the young insect and the development of the adult. 2.-Young nymph of the seventeen-year-old cicada, and change in the foreleg from nymph (B) to adult (C).
EVOLUTION OF THE ADULT
The association of the larval endopterous state with holometabolism is probably internal. This fact determines the essential structure not only of the adult lepidopteron, but also of the caterpillar.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS
In the tent caterpillar moth (fig. 4 A), for example, the esophagus (Oe) is a long slender tube. According to Burgess, the delicate walls of the diverticulum are well supplied with slender longitudinal and transverse muscles.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS II
THE CATERPILLAR
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 13
8 A) the latter (Vent) can extend from the thorax to the seventh segment of the abdomen. In a study of Papilio larvae, which feed almost exclusively on screen-laden plants, Dethier shows that the attractive smell is that of the. A typical caterpillar probene (fig. 9 A, G, J) is a short, thick, hollow outgrowth of the body wall known as a flattened foot lobe.
Since the Onychophora and Tardigrada have a leg muscle type similar to that of the caterpillar's front legs. Fracker (1930) and Peterson (1948) made comparative studies of the crochet from a taxonomic point of view without correlating their arrangement with the habits of.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 17
On the mesal surface of the pad (D) each hook is seen to be supported on what appears to be a slender vertical rod in the wall of the planta. The broad bases of the crochets are articulated by mesal points (F, a) in an even row on the plantar lobe (D). For the common free caterpillar, however, both the thorax and the abdominal legs are of little or no use for progression, and the caterpillars have developed a remarkable motor mechanism for direct movement of the body itself.
In addition, most caterpillars can twist and turn in all directions, and often, holding on to the prolegs, raise the front part of the body and wave it. When the resting caterpillar is about to move, the thoracic legs may first become active and slightly stretch the front part of the body, but they do not rise.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 21
Each segment contracts from the back and is then expanded forward by the next contraction of the segment. Since the motor force of the caterpillar's movement is the successive contraction of the body segments from back to front, so is locomotion. Other writers, such as Barth (1937) and Fiedler (1938), have attributed the movement of the caterpillar to the contraction of the segments without noticing the expansion.
However, Barth makes a detailed analysis of the muscles involved in the progressive movements of the caterpillar. The only organs not particularly involved in the adaptive specialization of the caterpillar are the heart, the tracheal system and the nervous system therein.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 25
Among the Neuroptera, some species secrete silk in the Malpighian tubules and spin it from the anus. Eltringham (1928) showed that the so-called balloon fly, Hilara of the Empididae, spins its silk from glands in the enlarged basal tarsomeres of the forelegs. The art of spinning silk was best cultivated by spiders, whose silk glands are in their abdomens.
Lesperon (1937) described the histology and physiology of the silk glands and the secretion of silk in the different groups of silk. The normal salivary glands of insects are located in the thorax; their ducts unite in a common outlet duct that opens into the space between the hypopharynx and the labium, known as the salivary gland.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 29
1, 2, j) from the hypopharynx placed on a sclerotic rod, or rhaphe (Rph), in the dorsal wall of the press, and a single pair. The lumen of the press is continued into a narrow exit tube (D) which opens at the end of the spinneret (Spn). The hypopharyngeal wall of the press is deeply bent (E) in the lumen (Lum), but apparently can be lifted by the muscles, and then by an elastic rebound propel the liquid silk.
As already noted, the maxillae are closely related to the labium, forming a prominent lobe on the underside of the head that holds the whorl (fig. 5 B,C), but the hypopharynx (Hphy) is also included in this structure, as it is united. with the inner wall of the labium (Lb). While these parts are movable by their own muscles, the characteristic figure eight movements of the spinning caterpillar are.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 3
1953) growth of adult antennae and mouthparts in larvae of Pieris brassicae. The adult antenna begins to develop in the first larval stage as a thickening of the epidermis below the larval organ. In subsequent stages, the base of the antenna moves up under the larval cuticle until it reaches the position of the adult facial organ.
Similarly, as Eassa shows, the rudiments of the adult maxillae appear in the first larval stage as a thickening of the epidermis beneath the larval maxillae. In some of the nematocerous diptera they are evaginated in the last larval stage under the larval cuticle, as the writer (1959) has noted in the mosquito.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 33
After a short rest period, the silk glands degenerate and during the winter some of the larval muscles are lost. These bodies are directly connected by nerves to the secretory centers of the brain, and a nerve from each corpus cardiacalum passes to the corpus allatum of the same side. This seems to indicate that the more brain secretion there is in the corpora cardiala, the less active the corpora allata are, and vice versa.
After prolonged exposure to low temperatures, the endocrine activity of the brain is restored, "diapause ends, and adult development ends. These writers suggest, therefore, that something of the nature of the juvenile insect hormone may be widely present in all animals , and that evolution has produced.
METAMORPHOSIS
Van der Kloot and Williams (1953) showed that the stimulus for spinning is of internal origin, partly hormonal and largely the state of the silk glands. In preparation for pupation, they spin a silk mat or cone on the underside of a twig or leaf or against some upright object, then hang onto it upside down with the help of the claws of the anal prolegs and spines on the suranal plate. As the pupa forms, it splits the larva's skin across its back and down its face.
However, according to Riley (1879), there are small ridges and knobs at the tip of the pupal abdomen that serve partly to grasp the floating larval skin, but are the main suspensorium. The tenth abdominal segment of the chrysalis is extended into a process known as the cremaster (or pendant), armed at the tip with spines and hooks.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 37
The wings are now turned out and the legs have more of the adult structure (H). With the final shedding of the larva's cuticle (pupal ecdysis), the fully formed pupa is released (Fig. 16 D). In the pupa of the tent caterpillar described here, however, the mouthparts actually regress from their developmental state.
The transformation of the muscular system varies in degree in different insects according to the difference in larval and adult musculature. Important imago muscles that have no representative in the larva are newly formed in the pupa.
NO. 6 CATERPILLAR AND BUTTERFLY — SNODGRASS 41 observed that the imaginal muscle rudiments must first be innervated
In particular, it would seem unusual for a flightless "nymph" stage of a lepidopteron to have an adult mouth. There is nothing improbable in the phenomenon of adult affection between doll and imago; adult moulting occurs in other arthropods, apterygote insects, and diopters. Experimentally, prayer can be initiated both in an adult insect and in
These glands in insects without a pupal stage degenerate at the moult into the adult, but in holometabolous insects they persist into the pupal stage.
LIFE OF THE ADULT
In these species, the shrunken silk glands of the caterpillar now secrete a clear liquid, which comes out of the mouth of the moth and softens the sticky coating of the cocoon threads, thus making it possible for moths. Trouvelot (1867) described the pre-emergence activities of Telea polyphemus as seen through a mica window inserted into the side of the cocoon. Then it makes powerful contractions and extensions of the body which force the head through the moistened silk.
Some of the moths and many of the butterflies are the most beautifully colored of living creatures, their only rivals being among the birds. Kellogg (1907) showed that the male of the silkworm moth finds a female entirely by her smell.
44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 to understand why so many of them are endowed with such brilliant
In the fall or early winter, when cold weather sets in, most of them simply die a peaceful death. Perhaps most commonly it is the pupa that hibernates, but in some species the larva lives through the winter, or it is winter. Within three weeks or a little longer, the young larvae are fully formed in the eggs.
Here they remain protected under the egg during the summer, autumn and winter to emerge early the following spring. Even within a single order, such as Lepidoptera, different species solved the problem of survival in different ways.
Feeding habits of the southern armyworm and rate of passage of food through its gut. Notes on the histology and anatomy of the larva of Bolitophila luminosa from New Zealand. On the development of the midgut in the larval stages of Vanessa urticae (Lepidoptera).
On the homology and nomenclature of the setae of lepidopteran larvae, with some notes on the phylogeny of Lepidoptera. XL Effects of nerve transection on the intercerebralis-cardiacum-allatum system of the insect Lettcophaea maderae.
NO. 6 CATERPILLAR AND EUTTERFLY — SNODGRASS 51
