282 



THE AMERICAN ENTOMOLOGIST. 



to Trypoxylo)!. We have similar cells 

 from Texas and other parts of the South. 

 They differ from those of Pelopceiis in 

 being wider, ribbed on the upper surface 

 and fastened not only side by side but in 

 long tubes end to end. The Pelopaus 

 spins a thin, yielding, semi-transparent, 

 elongate cocoon of a golden-brown color 

 with more or less loose silk around it, 

 and the tail end darkened and docked ; 

 the Trypoxyloii spins a tougher, thicker, 

 more solid and smooth cocoon of a dull, 

 bark-brown color, generally about half as 

 long as the other (but varying greatly 

 in size) and with the head-end often ex- 

 panding into a flange. 



We have reared what is very near, and 

 probably identical with, Argyrainmba fur 

 from larvse that had preyed on Trypoxyloii 

 albitarse which had made use of the mud 

 cells of Pclopoeus litnatiis, or the Common 

 Mud-dab, in Texas ; also from the same 

 wasp that had made use of the burrows 

 of a bee [AutJiophora abrupta Say). 



The larva of Ari:;yraiit(vba has very 

 much the same appearance as that of 

 Systoec/ms and Triodites, and the pupa is 

 distinguished from the pupa of this last 

 principally by its longer and more numer- 

 ous hairs, longer anal spines and more 

 conspicuous spiracles. 



The discovery of the "parasitism" of 

 these Bee-flies upon locust-eggs at once 

 suggests a comparison with the similar di- 

 versity of parasitic habits among the Me- 

 loidce as given in our First Report, some of 

 them infesting bee-cells, while others, as 

 the true Blister-beetles [Lyttini) feed on 

 locust eggs. 



The Anthracids are now united by the 

 best authorities with the Poinby/iidce, of 

 which family as a whole, Osten Sacken 

 has said;t they are "perhaps the most char- 

 acteristic and one of the most al)undantly 

 represented families of Diptera in the 

 western region, including California." The 

 abundance of Blister-beetles is also well 

 known to characterize this region, and we 

 have shown how this abundance is con- 

 nected with the abundance of Locusts. 



t L. r., p. 25.'), 



It is of interest, therefore, to find that the 

 Bee-flies bear a similar relationship of 

 parasitism to the latter and that the char- 

 acterization of the fauna in these two 

 groups is really dependent upon the pres- 

 ence of the Locusts as well as upon the 

 rich representation of the burrowing Hy- 

 menoptera. 



With these general remarks we will now 

 give a more full and descriptive account 

 of the two Bee-flies which, by rearing from 

 the larva, we know to have this locust-egg- 

 feeding habit. 



SVSTCKCHUS OREAS. 



The character of the eggs and the man- 

 ner in which they are laid have not yet been 

 observed. The larva (Fig. 147,^;) has already 

 been described in our First Report (p. 305) 

 and is found in the locust egg-pods or 

 near them, of different sizes, during most 

 I of the year. These larvae begin to trans- 

 form to the pupa state early in the sum- 

 j mer, and the pupa (,Fig. 148) jnishes itself 

 j half-way out of the ground in order to dis- 

 j close the fly. These flies continue to issue 

 j during the summer months. As a rule but 

 I one year is required for full development, 

 but there is in this respect great irregularity, 

 and the same tendency to retardation 

 which we have called attention to in the 

 case of the Blister-beetles. We have had 

 ([uite a number of the larvae remain over 

 unchanged till the second year, and all 

 that we have said as to the philosophy 

 of this retardation in the one case applies 

 in the other. We are inclined to think 

 that future observations will show, that 

 there is a still further parallel in that the 

 newly-hatched larv^ of the Bee-flies are 

 much more active than in the later stages, 

 and somewhat different in structure. 



The three later states of the insect may 

 be characterized as follows : 



[We omit the more detailed descrii)tive 

 parts of the article. With additional ma- 

 terial we have been enabled to examine 

 more fully the structure of the head than 

 we had in giving the original description.* 

 Underneath the median elevated piece. 



*Ninth Mo. Em. Kpt., p. 96. 



