10 THE CLASSIFICATION OF INSECTS 



comparative morphology of these parts. But perhaps this beginning will succes- 

 sively lead to a full understanding of the phenomenon ; and as these facts were 

 chiefly traced from the larva of Eudamus Tityrus, I shall describe more particu- 

 larly what I have observed in that species, and occasionally introduce some reference 

 to what I have seen in others. 



This butterfly lays its eggs separately, one by one, (Fig. 1, egg of natural size,) 

 upon the leaves of Robinia viscosa and pseudacacia, to which they are attached by a 

 broad, flattened surface. The walls of this attached surface are smooth, and much 

 thinner than the other part of the circumference of the eggs, which is otherwise 

 almost spherical (Fig. 1, a). Its color is grass-green. The upper rounded end 

 shows a small circular depression (Fig. 1, &), also thinner than the sides. The sides 

 are adorned by sixteen vertical ribs (Fig. 1, b and a*), which are denticulated 

 externally, eight of the ribs meeting the upper circular depression, while eight are 

 shorter. Some time before the caterpillar is hatched, it appears like a dark reddish- 

 brown band across the egg, about the middle of its height. At a later period, and 

 not long before it is hatched, the caterpillar may be seen through the shell of the 

 egg moving in jerks within its cavity. Its darker reddish color renders it then very 

 conspicuous. Though I have often tried to secure a sufficient number of these 

 eggs, I have not been able to trace the mode of formation of the larva itself within 

 the egg, and its changes during its ovarian growth. For those eggs which I have 

 had an opportunity of investigating, and one of which is represented in Fig. 1, I am 

 indebted to Dr. T. W. Harris, of Harvard University, whose extensive knowledge 

 and acquaintance with the metamorphoses of insects are too well known in the sci- 

 entific world to require notice from me. I can only state, that, when hatched, the 

 young caterpillar has the same form that it preserves throughout its growth. 



The head is already dark blackish, and shoWs two small orange spots above the, 

 outside of the mandibles. The collar is also darker than the following joints. 

 However, the color of the main body at that period does not contrast so much 

 with that of the head and collar as it does afterwards; the second and third thoracic 

 joints, and the whole series of abdominal joints being then reddish-orange, and 

 assuming only after the first moulting the same greenish-yellow color which it has 

 afterwards, and which is the final color of the animal. This fundamental color, 

 however, is not uniform, as we observe minute blackish spots about the stigmata, 

 and also upon the back, as well as several small greenish-black streaks across each 

 ring. (Figs. 2, 3, 4, 5, 6.) The thoracic legs are reddish, and the prolegs somewhat 

 orange. As in all caterpillars of Lepidoptera, the number of joints of the body is 

 thirteen, the head being considered as one, though, from various indications, we may 

 admit that it consists itself of three soldered segments. The thorax has three 

 joints, provided with three pairs of horny feet, terminating in a claw. There is, 

 however, a marked difference in the caterpillar between these three joints ; the first 

 being smaller and shorter than the second, and of a dark reddish-black color, 

 the joint between the head and collar reddish, and the collar itself reddish- 



* One of the ribs is still further enlarged in Fig. 1, c. 



