538 THEREVID.E 



humeral bristles but about four (two to six) pra;sutural in a row, two (or one) supra- 

 alar, one strong postalar, and usually one or two pairs of praescutellar ; other dorso- 



, . . central bristles only rarely present. 8cutelluni 



I ^ f ^ /^^y ""^ with two pairs of conspicuoiis slightly convergent 



/-"^^T^. . . ■^^'*\. /^ -^"^^S black marginal bristles, or one jmir only in 



/. • ■ ' ' ■ «^Y~"<r ^ Xestomyza. 



V/^Y^'^^x. Abdomen with seven (or more) segments, 



.-••■' ' ' \ J^ — ^ usually rather elongate and conical, and also 



-. . '^.. rr--;;:^--'^!.:^^'^-'''''^'^ usually bearing dense soft pubescence which is 



\^{-\^^^^:^^..^^^^^<^■ rather erect in the male but depressed in the 



V v^^^w^W"^ .Jf/^ female and which never includes any strong 



^"n\ inl \. M-^^ bristly hairs. Genitalia of the male rather long 



^^ — i/lvC~^\^-^ '^"*^^^ moderately conspicuous, but of the female 



/// W \ ■''^'^° ^^^ shining and bearing at the end a circlet 



^~<M^^ ^Ji of coarse black spines (fig. 319) similar to those 



^"^ which occur in some Mydaidce, Apiocerida\ Anth- 



Fio. 311. — Thcrcva nobiliU'ta f , x 10. riicince and A sifuhe 



Legs slender, rather long, and bearing distinct 

 bristles which are hardly macrochaetae and which are not adapted for predatory 

 ])urposes ; anterior coxae with two (or more) bristles in front near the tip, and the 

 hind coxae with one outside not so near the tip besides two or three small ones 

 in front at the tip; anterior femora often with about two (1-3) bristles beneath 

 near the middle and sometimes one behind ; hind femora usually with an irregular 

 row of antero-ventralliristles ; front tibiae with two or three rows of shorter bristles, 

 while the posterior tibiae have four rows, and all have an apical circlet of al>out 

 six spines, of which one almost anterior is conspicuously long on the front pair 

 but about four are long on the posterior jjairs ; tarsi rather thin and with small 

 circlets of bristles at the tip of each joint (except the last), though the circlets 

 are short and inconspicuous on the front pair ; posterior tarsi with short plantar 

 bristles on the basal joint, and the front tarsi sometimes wdth a few "touch-hairs" 

 on the underside. Pul villi two only or none ; empodium represented by a thin 

 bristle or absent. 



Wings (fig. 310) with a well marked and comparatively simple venation some- 

 what intermediate between that of the Tahanuke and that of the AsiliJce, but 

 distinguished from the former by the longer upper basal cell and the less wide open 

 cubital fork, and from the latter by the shorter subcostal vein. Subcostal vein 

 comimratively short ; praefurca fairly long and commencing long before the base of 

 the discal cell ; culntal vein with a simple fork, which is long but begins beyond 

 the end of the discal cell and is rather wide open and includes the wing-tip ; 

 discal cross-vein placed near the middle of the discal cell, and consequently the 

 upper basal cell longer than the second ; discal cell always well defined and entirely 

 composed of the discal vein, as the small cross-vein is distinctly present ; discal cell 

 ahyays_ emitting three veinlets to (or towards) the wingniargin, which are either 

 (juite simple or the lower one may curve down enough to join the upper branch of 

 the postical fork and thereby cause a closed fourth posterior cell ; postical vein with 

 a well defined simple fork, of which the upper branch is connected by the small 

 cross-vein to the discal cell near the base of the latter, and this branch is usually 

 joined by the third veinlet from the discal cell close to the wingniargin, while, 

 the lower branch is always united with the anal vein near the wing- 

 margin so as to form a closed anal cell ; submarginal cells always two ; posterior 

 cells always five. Wing-inembrane crowdedly but not very distinctly rippled, 

 minutely pubescent. .Squamae with only the alar pair developed, but they are 

 rather large and peculiarly folded so that the strongly defined margin is angled 

 about the middle and gives an impression of there being two pairs of squama? ; 

 fringe above that fold rather short, even, and delicate, but after the fold long and 

 similar to the pubescence on the neighboring part of the metapleurae when there is 

 long pubescence there but otherwise with only a moderate fringe ; frenum distinct. 

 Halteres in no way concealed, and with the upper part of the stem widening out to 

 the knob. 



The metamorphoses in all stages are not satisfactorily known, but the 

 young larvae are very mobile in hunting for prey; they are serpentine 



