I have told how, while digging in search of the Sitaris, I found two cells belonging to Meloe cicatricosus. One contained an Anthophora's egg; with this egg was a yellow Louse, the primary larva of the Meloe. The history of this tiny creature we know. The second cell also was full of honey. On the sticky liquid floated a little white larva, about a sixth of an inch in length and very different from the other little white larvæ belonging to Sitares. The rapid fluctuations of the abdomen showed that it was eagerly drinking the strong-scented nectar collected by the Bee. This larva was the young Meloe in the second period of its development.
I was not able to preserve these two precious cells, which I had opened wide to examine the contents. On my return from Carpentras, I found that their honey had been spilt by the motion of the carriage and that their inhabitants were dead. On the 25th of June, a fresh visit to the nests of the Anthophoræ furnished me with two larvæ like the foregoing, but much larger. One of them was on the point of finishing its store of honey, the other still had nearly half left. The first was put in a place of safety with a thousand precautions, the second was at once immersed in alcohol.
These larvæ are blind, soft, fleshy, yellowish white, covered with a fine down visible only under the lens, curved into a fish-hook like the larvæ of the Lamellicorns, to which they bear a certain resemblance in their general configuration. The segments, including the head, number thirteen, of which nine are provided with breathing-holes with a pale, oval rim. These are the mesothorax and the first eight abdominal segments. As in the Sitaris-larvæ, the last pair of stigmata, that of the eighth segment of the abdomen, is less developed than the rest.
The head is horny, of a light brown colour. The epistoma is edged with brown. The labrum is prominent, white and trapezoidal. The mandibles are black, strong, short, obtuse, only slightly curved, sharp-edged and furnished each with a broad tooth on the inner side. The maxillary and labial palpi are brown and shaped like very small studs with two or three joints to them. The antennæ, inserted just at the base of the mandibles, are brown, and consist of three sections: the first is thick and globular; the two others are much smaller in diameter and cylindrical. The legs are short, but fairly strong, able to serve the creature for crawling or digging; they end in a strong black claw. The length of the larva when fully developed is one inch.
As far as I can judge from the dissection of the specimen preserved in alcohol, whose viscera were affected by being kept too long in that liquid, the nervous system consists of eleven ganglia, not counting the oesophageal collar; and the digestive apparatus does not differ perceptibly from that of an adult Oil-beetle.
The larger of the two larvæ of the 25th of June, placed in a test-tube with what remained of its provisions, assumed a new form during the first week of the following month. Its skin split along the front dorsal half and, after being pushed half back, left partly uncovered a pseudochrysalis bearing the closest analogy with that of the Sitares. Newport did not see the larva of the Oil-beetle in its second form, that which it displays when it is eating the mess of honey hoarded by the Bees, but he did see its moulted skin half-covering the pseudochrysalis which I have just mentioned. From the sturdy mandibles and the legs armed with a powerful claw which he observed on this moulted skin, Newport assumed that, instead of remaining in the same Anthophora-cell, the larva, which is capable of burrowing, passes from one cell to another in search of additional nourishment. This suspicion seems to me to be well-founded, for the size which the larva finally attains exceeds the proportions which the small quantity of honey enclosed in a single cell would lead us to expect.
Let us go back to the pseudochrysalis. It is, as in the Sitares, an inert body, of a horny consistency, amber-coloured and divided into thirteen segments, including the head. Its length is 20 millimetres.1 It is slightly curved into an arc, highly convex on the dorsal surface, almost flat on the ventral surface and edged with a projecting fillet which marks the division between the two. The head is only a sort of mask on which certain features are vaguely carved in still relief, corresponding with the future parts of the head. On the thoracic segments are three pairs of tubercles, corresponding with the legs of the recent larva and the future insect. Lastly, there are nine pairs of stigmata, one pair on the mesothorax and the eight following pairs on the first eight segments of the abdomen. The last pair is rather smaller than the rest, a peculiarity which we have already noted in the larva which precedes the pseudochrysalis.
1 .787 inch.—Translator's Note.
On comparing the pseudochrysalids of the Oil-beetles and Sitares, we observe a most striking similarity between the two. The same structure occurs in both, down to the smallest details. We find on either side the same cephalic masks, the same tubercles occupying the place of the legs, the same distribution and the same number of stigmata and, lastly, the same colour, the same rigidity of the integuments. The only points of difference are in the general appearance, which is not the same in the two pseudochrysalids, and in the covering formed by the cast skin of the late larva. In the Sitares, in fact, this cast skin constitutes a closed bag, a pouch completely enveloping the pseudochrysalis; in the Oil-beetles, on the contrary, it is split down the back and pushed to the rear and, consequently, only half-covers the pseudochrysalis.
The post-mortem examination of the only pseudochrysalis in my possession showed me that, similarly to that which happens in the Sitares, no change occurred in the organization of the viscera, notwithstanding the profound transformations which take place externally. In the midst of innumerable little sacs of adipose tissue is buried a thin thread in which we easily recognize the essential features of the digestive apparatus, both of the preceding larval form and of the perfect insect. As for the medullary cord of the abdomen, it consists, as in the larva, of eight ganglia. In the perfect insect it comprises only four.