THE AMERICAN ENTOMOLOGIST. 



283 



[Fig. 1.50.] 



which may represent the labrum, we find 

 two stout spines faintly notched on the 

 outer edge, which are doubtless the man- 

 dibles, and correspond to the two dark 

 lance-like mandibles of other Dipterous 

 larvi\}, for they are retractible and run back 

 into the thoracic joints, and remain after 

 the other trophi are detached. The pair 

 of feelers upon the upper lateral pieces, 

 which seem to have no motion, might then 

 represent the antenna;, and the two lower 

 jjieres, the maxilla; with their palpi ; while 

 the labium is shown in a chitinous i)oint 

 visible only when the larva extends and 

 raises the outer parts. A peculiarity in 

 the movement of the maxillx or lower 

 pair of horny pieces is worthy of note. 

 They move in alternation with one another 

 in the forward and backward, /. e. up and 

 down, motion. The i)alpus of these lower 

 pieces when viewed from 

 abo\ e is circular, with two 

 dark marks indicating mi- 

 nute appendages. When the 

 larva is fresh and plump it 

 is almost white and shows 

 most plainly the swelling 

 of the thoracic joints and 

 the translucences. Toward 

 the period of pupation it 

 becomes more opaque and 

 more contracted.* 

 I'he pupa (Fig. 14S) averages 8.5""" in 

 length. The color is honey- yellow, but 

 varies with age, the head and thorax assum- 

 ing a dark color with maturity. The per- 

 fect fly (Fig. 149) is at once distinguished 

 from the succeeding species by its broader 

 form and long proboscis. The whole 

 body is covered with long yellow or ful- 

 vous hairs. The species varies in the 

 color of the legs and in size, some females 

 being larger than the males. The species 

 was originally described from Sierra Co., 

 Cal., and Mr. Williston informs us that 



Triodites mus: 

 pupa (after Riley). 



he has a specimen from Washington 

 Territory. 



TRionrrKs i\irs. 



The habits of this insect in the larva 

 state are precisely like those of the pre- 

 ceding, and the larva so greatly resembles 

 that of the Systa'chiis that it is well nigh 

 impossible to separate the two with cer- 

 tainty. The head parts are somewhat 

 broader, shorter and less flattened, the 

 maxillae more blunt, the labrum paler, and 

 the mandibles sharper and with a smoother 

 outer edge. The thoracic joints bulge 

 less beneath and the thoracic spiracle is 

 more sunken and less conspicuous. The 

 pupa (Fig. 150) is easily distinguished from 

 that of Systa-cJiiis in the broader and more 

 bulbous head, and in many structural 

 characters. 1'he larger head and eyes, 



[Fis. 151.1 



* So far as we can ascertain there has hitherto been published 

 no recognizable figure or description of the Bombyliid larva. 

 Dufour, in his article above alluded to, describes that of 

 Jicimliyliits major very indifferently, and gives a dorsal view 

 which shows little or no relation to the larva here described, 

 wiiile his description and figure of the mouth parts fail to in- 

 dicate the different pieces w(- have observed in our larva;. Yet 

 in general form and structure the true Bomhylius larva will 

 undoubtedly be found to agree very closely with those here 

 described. 



Triodites mus : female (after Riley). 



more slender form and short proboscis 

 readily distinguish the fly from the Sys- 

 ta-c/ii/s. The sexes are also readily sepa- 

 rated by the more pronounced transverse 

 rows of white or tawny hairs on the hind 

 borders of the abdominal joints in the 

 female (Fig. 151 . The genus in some 

 degree connects the Aiithracini with the 

 more typical Bombyliini. In certain lights 

 the tegument reveals a greenish tinge, and 

 the pubescence of the thorax appears 

 generally of a tawny color. The male 

 sometimes has a white tomentum on the 

 front, and in some specimens there is a 

 stump of a vein extending into the discal 

 cell. As the Triodites is not yet known 

 to occur east of Utah, we conclude that 

 Systa'chus is the genus most affecting the 

 locusts in the Mississippi Valley. J 



