Pupation

“ When it is a pupa it rests in a case or cradle shaped much like a hen’s egg. There the pupa lies, its legs folded over the front of its body, its wings packed by its side, its jaws and feelers laid on its breast. It looks very much like a baby laid asleep in a bed. It is not pretty like a dear baby. In fact, it is ugly to look at.
The larva could eat, walk, roll, or swim. The pupa in this little case can do nothing but wait. [Pg 81] The full-grown beetle can fly, swim, eat, walk, and is often a thing of great beauty. ”

“ When full grown they leave the water, crawling out on the damp shore of the pond or stream, and burrow into the soil for a few inches. Here they molt again, or pupate as it is called, changing to a non-feeding, quiescent stage called the pupal stage. The pupa is the stage in which the great changes from wingless, crawling and swimming, short-legged, long, slender-bodied larva to winged, swimming and flying, long-legged, compact, broad-bodied adult are completed. Late in the summer or in the fall the pupal skin breaks and the adult issues. ”

“ The period of transformation being come, the pupa goes to the water-side, and fixes on a plant, or sticks fast to a piece of dry wood, in which position it remains for some little time, when the skin of the nymph splitting at the upper part of the thorax, the winged insect issues forth gradually, throws off its slough, expands its wings, flutters, and then flies off with gracefulness and ease. The elegance of its slender shape, the richness of its colours, the delicacy and resplendent texture of its wings, render it a beautiful object. ”

“ If the call of the female comes from the ground, all the males immediately fly towards the spot, and the moment they reach it, whether the hen be in sight or not, spread out and erect their tail, draw the head back on the shoulders, depress their wings with a quivering motion, and strut pompously about, emitting at the same time a succession of puffs from the lungs, and stopping now and then to listen and look. But whether they spy the female or not, they continue to puff and strut, moving with as much celerity as their ideas of ceremony seem to admit. ”

“ When it is full-fed, and about to enter the pupal state, it proceeds to prepare its habitation. As a larva, when it desired to feed, it protruded its head and the front of its body from the mouth of the tube, and then crawled about in search of nourishment, dragging the tube with it, and holding it firmly by means of the claspers with which the end of the body is furnished. But when it becomes a pupa it is no longer able to defend itself, and is instinctively compelled to secure its safety in some peculiar manner. ”

“ Furthermore, the pupa, though one in the strict sense, is capable of great freedom of movement, its head, mouth-parts, antennæ, legs and wings, ensheathed by the cuticle, being freely movable, and not rigidly attached to the body. ”

“ But the escape of the pupa, when about to undergo its last metamorphosis, is as interesting as the fact of its closing the shutters to announce its own death. It is provided with a pair of hooked mandibles, with which to gnaw through the grating, and no sooner have these accomplished their purpose than they fall off, and the pupa takes its last shape of a four winged fly, as represented in the cut. ”

“ The pupal stage is characteristic of the life-story of those insects whose larvae have wing-rudiments in the form of inpushed imaginal discs, and in all these insects there is, as we have seen, considerable divergence in form between larva and imago. In the pupa the wings and other characteristically adult structures are, for the first time, visible outwardly; it is the instar which marks the great crisis in transformation. ”

“ In other species, on the contrary, such as the dog, the rabbit, the guinea-pig, etc., where several broods of young are produced during the year, or where, as in the human subject, the generative epochs of the female recur at short intervals, so that the particular period of impregnation is comparatively indefinite, the generative apparatus of the male is almost always in a state of full development; and is excited to action at particular periods, apparently by some influence derived from the condition of the female. ”

“ When the pupa had slept the appointed time, the animal, still resident within the habitaculum formed by the larva, was found to open the carina by the motion of its head, and prepare to receive the winged male. Here, therefore, we have an animal which in its adult state is for ever excluded from the light, and never even beholds the mate to which it is indebted for its progeny. ”

“ The male and female frequently work together at the task of preparing the nest. When oviposition is about to take place, the male may be seen to suddenly attach himself to the dorsal surface of the head of the female which holds on to one of the stones at the upper margin of the nest. The urogenital opening of the male, with its specially prominent papilla, is approximated to that of the female, and with a peculiar quivering movement the eggs and sperms are emitted synchronously amidst clouds of sand stirred up by the movements of the tail. ”

“ As a matter of fact many of the special organs of the adult, the legs and wings, for example, begin to develop as little buds or groups of cells in the body of the larva, and when the larva is ready to pupate these imaginal wings and legs are drawn out to the external surface of the body, and may be readily recognized as they lie on the ventral surface of the pupa folded and closely pressed to the body surface. ”

“ The internal organs of reproduction in the female consist of the ovaries, from which the eggs pass by way of the oviduct to the ovipositor, which in butterflies is not so conspicuous or remarkable an organ as is the case in many other insects. Communicating with the oviduct are the spermatothecæ, which are receptacles in which is retained the fertilizing fluid received from the male at the time of coition. As the eggs, one by one, are passed from the ovaries into the oviduct, they are impregnated through absorption of the spermatozoa, which enter their walls, imparting to them vitality. ”

“ The puppies are born singly, and if a bitch has a large litter they generally come in twos and threes, with a very short interval between the items of each brace or trio, and a long rest between the batches. The first services the mother has to render her babies are to free them from the bag of membranes in which they are born, and to bite the cord which joins each puppy to the afterbirth—a fleshy substance which comes away with or shortly after it. All animals intensely dislike being watched while they perform these operations ”

“ The pupa either shows the appendages of the perfect insect, though these are encased in a sheath and adherent to the body, or else it is entirely concealed within the hardened and contracted larval integument, which forms a barrel-shaped protecting capsule or puparium. ”

“ Through this rent the tail of the pupa is brought and firmly anchored in the silk by a few vigorous strokes, the insect hanging meanwhile to the skin which has not been quite cast off on the reverse side to the rent. When thus firmly attached to the silken pad, the pupa shakes itself entirely free, whirling itself round and round until the old skin is dislodged from the silk and falls to the ground. The two usual varieties of pupæ are shown at Figs. ”

“ If, however, you require the imagines for breeding, you must be careful that the eggs are not laid long before the buds of the necessary food plants are due.
When you are expecting the appearance of perfect insects, the [Pg 121] pupa boxes should be examined every day. A morning visit to your pupæ (for most insects emerge in the morning) may reward you with the sight of a newly emerged imago, clinging to the rough surface of the box, thus affording you an opportunity of observing the wonderful expansion of the wings. ”

“ The pupa stage is easily affected by temperature changes and may be prolonged during hibernation for as long as 4 or 5 months. Numerous rearing experiments in various parts of the country have shown that the shortest time between the deposition of eggs and the emergence of the adult fly is 8 days, and 10 and 12 day records were very common.
The adult fly, upon emerging from the puparium, works its way upward through the soil or manure and upon reaching the air it crawls about while its wings expand and the body hardens and assumes its normal coloration. ”

“ The Puffin never lays more than one egg, unless the first may have been destroyed or taken away; nor does it raise more than a single young one in the season. The time of incubation is probably from twenty-five to twenty-eight days, although I have not been able to ascertain the precise period. Both birds work in digging the hole, using their bills and feet; they also sit alternately on their egg, although the female engages more industriously in this occupation, while the male labours harder at the burrow. ”

“ On first emerging, the pupa measures about 6·5 mm., the head and thorax making up one-third of this. During the last larval stage many of the pupal organs have been re-forming and are more or less visible through the cuticle. The mouth parts and limbs of the third stage—the future imago—show no relation to those of the [Pg 92] larva. They are there enclosed in their respective sheaths, but these are quite independent of the larval ‘appendages.’ The respiratory trumpets, which, as in the larva, pierce the surface-film, are ready to act as breathing-organs. ”

“ The larva without legs, a distinct head being often absent. The pupa inactive, the limbs of the imago firmly attached to the body, but plainly visible. Among the majority of species included in this Order the larval skin is not cast away, but envelopes the insect in a hard shell; the true pupa is consequently only visible on the removal of this covering, when it is found to closely resemble those in which no such arrangement occurs. ”

“ The pupa, or nymph, differs from the larva by its much shorter, compressed form; by being encased in a remarkably hard shell; and by the antennae approximating in form to those of the adult. It has short wing-pads at the sides of the body; the front legs are remarkably powerful, and the creature is capable of moving about; the imago escapes from the pupa by the splitting dorsally of the middle of the thoracic segments. ”

“ In a few seconds the pupa makes several slow, but powerful, respiratory efforts; during which the abdominal segments become more contracted along their under surface, and the wings are much enlarged and extended along the lateral inferior surface of the body, while a very transparent fluid, which facilitated the slipping off of the skin, is now diffused among the limbs, and when the pupa becomes quiet dries, and unites the whole into one compact covering. ”

“ As regards the breeding of this species, a fact of considerable interest was noticed. In the pouch of the female (which, by the way, has the opening turned towards the anus) as a rule three young are found in the earliest stage of development after birth. When the half-grown post-foetal stage is reached only two remain; and when development is nearly completed, and the young animal almost fit to leave the pouch, only one is left. ”

“ Characters from the larva and pupa.
Larva depressed, kaned; has sixteen feet, lives through one or more winters, never rolls itself in a ring when touched, feeds on the solid interior woody parts of vegetables; pupa changes in a tough cocoon, in which are interwoven particles of the larva's food; it has a double row of small raised denticulations on each segment of the abdomen, which give it partially the power of locomotion. ”

“ Incubation means lying upon. The brooding bird does in fact crouch or lie upon her eggs, warming them with the heat of her body for a number of days with indefatigable patience. When a hen wishes to set,1 she makes it known by her repeated cluckings, little cries of maternal anxiety, by her ruffled feathers, her restless movements, and particularly by the perseverance with which she stays on the nest, even when it has no eggs, where she has been in the habit of laying. ”

“ Russ was always careful either personally to describe, or to obtain accurate descriptions of, the young plumage of all birds bred in captivity, from the egg until the change to the adult plumage; he noted the character and number of eggs, the duration of incubation, the age at which the young left the nest, and that at which their adult plumage was attained. ”

“ His efforts to induce a hen or a rooster to play with him are pathetic. The hen cannot understand. She hasn’t a particle of play in her anyhow, but Pups cannot get that through his head. He runs rapidly around her, drops on all fours flat, swings his tail, cocks his ears, looks appealingly and barks a few little cackle-barks, as nearly hen-like as he can bark them, then dashes off and whirls back—while the hen picks up another bug. She never sees Pups. ”

“ Where a sire must be chosen from among strangers, his points should correct any in which the bitch is deficient; your toy pug may have too small a head, with little wrinkle—you must look for a dog with good head properties as her mate; your Pom may be long in back, and you must seek a male with the opposite quality, and a plume well over and touching his frill.
The first puppies of two young dogs are generally larger than the parents, but I do not believe the theory often advanced that the first litter is always the best. Puppies by a very old sire are usually small. ”