1 6 CHARLES T. BIUI -. 



described and beautifully figured by Marchal ('06). Here the 

 first larval >t.i.^ J which he has termed the Cyclops-larva is com- 

 posed of an enormous cephalo-thorax, bearing a pair of absurdly 

 enlarged jaws, and a slender abdominal portion. In the course 

 of later development the abdomen enlarges, the jaws are cast off 

 and the later stages assume the obese form characteristic of 

 many larva? of the higher Hymenoptera. Somewhat similar 

 cyclopoid or highly modified larva' are known to occur in a 

 number of widely scattered genera and it will be doubtless found 

 that this stage will greatly supplement any knowledge concerning 

 the natural affinities of the very numerous and closely similar 

 species. It is probable also that the structure of the larvae will 

 be found to reflect much more clearly the diversified behavior 

 of these insects than does the structure of the imago. 



As a rule the larger species of the parasitic Hymenoptera show 

 less modification, but in a few of the small number of forms that 

 have been studied, the early larva? is provided with unusual 

 structures of one kind or another. Most frequently the man- 

 dibles are noticeably enlarged. 



Some of the members of this same group exhibit a very interest- 

 ing phenomenon in the development of an early larva of typical 

 campodeiform appearance which simulates very closely the first- 

 stage larva of certain Meloid beetles and of the Strepsiptera. 

 This hymenopterous planidium is, of course, not by any means 

 identical with the triungulin in the other two orders, but presents 

 many features in common w r ith it. It will be noted also that it is 

 the early larva and not the later one that is of the campodeiform 

 type. The reason for the presence of a very active young larva 

 is clear in all three cases, as the larva actually finds its own host, 

 and is dependent upon its own resources at this early age. Here 

 it is very evident that the planidium and triungulin have been 

 interpolated in the larval development just as the whole larval 

 stage has been added to the life-cycle of the metabolous insects. 

 Their presence, especially in Hymenoptera is quite secondary. 



Aside from those of (he saw-flies, the larva? of ants should be 

 more susceptible to taxonomic treatment than those of other 

 Hymenoptera. In general, these do not possess such remark- 

 able modifications as occur in some of the para-it ir families, but 



