Lastly, we count nine pairs of stigmata: one pair on the mesothorax and the rest on the first eight segments of the abdomen. The last pair, that on the eighth abdominal segment, consists of stigmata so small that to detect them we have to gather their position by that in the succeeding states of the larva and to pass a very patient magnifying-glass along the direction of the other pairs. These are as yet but vestigial stigmata. The others are fairly large, with pale, round, flat edges.
If in its first form the Sitaris-larva is organized for action, to obtain possession of the coveted cell, in its second form it is organized solely to digest the provisions acquired. Let us take a glance at its internal structure and in particular at its digestive apparatus. Here is a strange thing: this apparatus, in which the hoard of honey amassed by the Anthophora is to be engulfed, is similar in every respect to that of the adult Sitaris, who possibly never takes food. We find in both the same very short oesophagus, the same chylific ventricle, empty in the perfect insect, distended in the larva with an abundant orange-coloured pulp; in both the same gall-bladders, four in number, connected with the rectum by one of their extremities. Like the perfect insect, the larva is devoid of salivary glands or any other similar apparatus. Its nervous system comprises eleven ganglia, not counting the oesophageal collar, whereas in the perfect insect there are only seven: three for the thorax, of which the last two are contiguous, and four for the abdomen.
When its rations are finished the larva remains a few days in a motionless condition, ejecting from time to time a few reddish droppings until the digestive canal is completely cleared of its orange-coloured pulp. Then the creature contracts itself, huddles itself together; and before long we see coming detached from its body a transparent, slightly crumpled and extremely fine pellicle, forming a closed bag, in which the successive transformations will take place henceforth. On this epidermal bag, this sort of transparent leather bottle, formed by the larva's skin detached all of a piece, without a slit of any kind, we can distinguish the several well-preserved external organs: the head, with its antennæ, mandibles, paws and palpi; the thoracic segments, with their vestiges of legs; the abdomen, with its chain of breathing-holes still connected one to another by tracheal threads.
Then beneath this pellicle, which is so delicate that it can hardly bear the most cautious touch, we see a soft, white mass taking shape, a mass which in a few hours acquires a firm, horny consistency and a vivid yellow hue. The transformation is now complete. Let us tear the fine gauze bag enclosing the organism which has just come into being and direct our investigation to this third form of the Sitaris-larva.
It is an inert, segmented body, with an oval outline, a horny consistency, just like that of pupæ and chrysalids, and a bright-yellow colour, which we can best describe by likening it to that of a lemon-drop. Its upper surface forms a double inclined plane with a very blunt ridge; its lower surface is at first flat, but, as the result of evaporation, becomes more concave daily, leaving a projecting rim all around its oval outline. Lastly, its two extremities or poles are slightly flattened. The major axis of the lower surface averages half an inch in length and the minor axis a quarter of an inch.
At the cephalic pole of this body is a sort of mask, modelled roughly on the head of the larva, and at the opposite pole a small circular disk deeply wrinkled at the centre. The three segments that come after the head bear each a pair of very minute knobs, hardly visible without the lens: these are, to the legs of the larva in its previous form, what the cephalic mask is to the head of the same larva. They are not organs, but indications, landmarks placed at the points where these organs will appear later. On either side we count nine stigmata, set as before on the mesothorax and the first eight abdominal segments. The first eight breathing-holes are dark brown and stand out plainly against the yellow colour of the body. They consist of small, shiny, conical knobs, perforated at the top with a round hole. The ninth stigma, though fashioned like the others, is ever so much smaller; it cannot be distinguished without the lens.
The anomaly, already so manifest in the change from the first form to the second, becomes even more so here; and we do not know what name to give to an organism without a standard of comparison, not only in the order of Beetles, but in the whole class of insects. While, on the one hand, this organism offers many points of resemblance to the pupæ of the Flies in its horny consistency, in the complete immobility of its various segments, in the all but absolute absence of relief which would enable one to distinguish the parts of the perfect insect; while, on the other hand, it approximates to the chrysalids, because the creature, to attain this condition, has to shed its skin, as the caterpillars do, it differs from the pupa because it has for covering not the surface skin, which has become horny, but rather one of the inner skins of the larva; and it differs from the chrysalids by the absence of mouldings which in the latter betray the appendages of the perfect insect. Lastly, it differs yet more profoundly from the pupa and the chrysalis because from both these organisms the perfect insect springs straightway, whereas that which follows what we are considering is simply a larva like that which went before. I shall suggest, to denote this curious organism, the term pseudochrysalis; and I shall reserve the names primary larva, secondary larva and tertiary larva to denote, in a couple of words, each of the three forms under which the Sitares possess all the characteristics of larvæ.
Although the Sitaris, on assuming the form of the pseudochrysalis, is transfigured outwardly to the point of baffling the science of entomological phases, this is not so inwardly. I have at every season of the year examined the viscera of the pseudochrysalids, which generally remain stationary for a whole year, and I have never observed other forms among their organs than those which we find in the secondary larva. The nervous system has undergone no change. The digestive apparatus is absolutely void and, because of its emptiness, appears only as a thin cord, sunk, lost amid the adipose sacs. The stercoral intestine has more substance; its outlines are better defined. The four gall-bladders are always perfectly distinct. The adipose tissue is more abundant than ever: it forms by itself the whole contents of the pseudochrysalis, for in the matter of volume the insignificant threads of the nervous system and the digestive apparatus count for nothing. It is the reserve upon which life must draw for its future labours.
A few Sitares remain hardly a month in the pseudochrysalis stage. The other phases are achieved in the course of August; and at the beginning of September the insect attains the perfect state. But as a rule the development is slower; the pseudochrysalis goes through the winter; and it is not, at the earliest, until June in the second year that the final transformations take place. Let us pass in silence over this long period of repose, during which the Sitaris, in the form of a pseudochrysalis, slumbers at the bottom of its cell, in a sleep as lethargic as that of a germ in its egg, and come to the months of June and July in the following year, the period of what we might call a second hatching.
The pseudochrysalis is still enclosed in the delicate pouch formed of the skin of the secondary larva. Outside, nothing fresh has happened; but important changes have taken place inside. I have said that the pseudochrysalis displayed an upper surface arched like a hog's back and a lower surface at first flat and then more and more concave. The sides of the double inclined plane of the upper or dorsal surface also share in this depression occasioned by the evaporation of the fluid constituents; and a time comes when these sides are so depressed that a section of the pseudochrysalis through a plane perpendicular to its axis would be represented by a curvilinear triangle with blunted corners and inwardly convex sides. This is the appearance displayed by the pseudochrysalis during the winter and spring.