On the Antennae, and Trophi of Lepidopterous Larvce. 13 



around its anterior margin. In the ordinary form it is always, except 

 in the genera Tischeria, Antispila, Aspidisca and Nepticula, more or 

 less deeply cleft in the center, dividing it into two lobes, but the size of 

 this notch varies in closely related species of the same genus; thus, 

 e. in fig. 58 the labrum of Gracillaria eupatoriella, it is small, 

 while in other species of the genus the labrum is scarcely distinguishable 

 from that of some species of Lithocolletis (fig. 33). Reaumur long 

 ago alluded to the office of this cleft in the economy of larvae which 

 feed upon the edges of leaves. The edge passes into the cleft and 

 back between the fore feet, the head being moved forward and back- 

 ward along it; and Prof. P. Martin Duncan, in his interesting and 

 valuable work upon the Transformation of Insects, and other writers 

 seem to consider it a special adaptation of structure to function. But 

 what shall we then say to its presence, equally as well developed in pro- 

 portion to the size of the larvae, in many of the little leaf mining species 

 (Lithocolletis, of the cylindrical and ornatella groups, Gracillaria, 

 etc. (figs. 33 and 59), which never see the edge of a leaf unless it be 

 from the inside of it? In the " ordinary form," the labrum is 

 less ciliated on its lower surface than it is in the first form, but 

 it is always armed on that surface with three teeth, though they are 

 sometimes difficult to detect in some of the more degraded forms 

 of the Tineina. It is always armed on its upper surface with certain 

 bristles, and the number of these seem to give us some assistance in 

 classifying the species. In Phyllocnistis the tropin of the ordinary 

 form are greatly atrophied, and I have been able to detect but two mi- 

 nute hairs on the labrum. But in all of the other genera and species 

 having the first form of trophi in their earlier stages, the labrum of 

 the ordinary form has ten bristles, and so has that of Mr. Riley's gonus 

 Prodoxus. Whether this indicates any relationship between Prodox- 

 us and the genera having trophi of the first form, remains to be 

 determined when we know the larvae of Prodoxus in its first stage. 

 This larva is certainly a very singular one in many respects, and the 

 pupa is armed with the cephalic tooth as in those species, as is also 

 that of Pronuba, though both have the anal hooklets terminal and not lat- 

 eral. Mr. Riley thinks that these two genera must have been derived from 

 a common ancestor, basing his opinion, however, on the fact that both 

 feed on Yucca (in very different ways, however), and on the resem- 

 blances of the moths, which, however, are only in ornamentation and 

 size, while the differences in habits of the larvae, and in the structure 

 of the larvae, pupae and imago are very great, and show that if they are 



