596 SCENOPINID^ 



5 First posterior {or suhapical) cell, in tliis family really praeapical. 



6 Discal cell. 



6* Second posterior cell. 



7 Postical {or ^rd, hut the normal 5th, posterior) cell {or 2iostical fork-cell). 



8 Axillary cell. 



9a Upper {or \st) basal cell. 

 9b Second {or middle) basal cell. 

 9" Anal {or Zrd basal) cell. 

 10 Alula. 



Notes on the Venation of the Scenopinid^. 



The chief peculiarities of the venation lie in (1) the short subcostal vein, (2) the 

 reduction of the discal vein, and (3) the upturned cubital and discal veins. 



1. The Subcostal Vein is unusually short, as it extends hardly beyond half 

 the wing, and in this character the Scenopinidce are extremely different from the 

 Mi/daidce, though they may show some similarity to their other allies, the 

 Therevida;. 



2. The Discal Vein is more reduced than in any other family of the 

 Brachycera, as its lower branch completely anastomoses into the upper branch 

 of the postical vein, and consequently the discal vein consists of only a simple * 

 continuous vein which throws down two cross-veins to this upper branch of the 

 postical vein and thereby forms the discal cell. The Discal Cell consequently 

 can only have four sides, but is long and narrow and gradually widening from base 

 to end ; it emits only one veinlet (besides the upper branch of the postical fork), and 

 that slopes upwards and reaches the wingmargin before the wing-tip. 



_ 3. The two branches of the cubital fork and the single veinlet from the discal 

 vein slope (rather than curve) up into the foremargin of the wing, and this 

 peculiarity is limited to this family and the Jlj/daidce and (to a certain extent) 

 the A])ioceridce. 



Other points of interest exist in the form and position of the cubital fork ; 

 the complete absence of an ambient vein after the end of the discal vein ; the 

 position of the discal cross-vein near the middle of the discal cell, so completely 

 different from that of the Mydaidce (except Megascelus) ; the presence of only one 

 posterior cell between the first and the normal fifth ( = postical fork-cell). Some 

 writers have professed to see a similarity in the venation to that of Pachygaster or 

 Beris or Xylomyia, but the complete absorption of the lower branch of the discal 

 vein, the shape of the discal cell, and the single veinlet from the discal cell show 

 very great distinctions. 



SCENOPINUS. 



Scenopinus Latreille, Hist. Nat. Crust. Ins., iii., 463 (1802). 



Rather small oblong blackish flies, with short simple-veined 

 wings, and with elongate drooping antennae which are without 

 any style or arista. 



Head transverse, short semicircular, being flatfish behind or slightly excavated 

 there against the vertex, not crammed on to the thorax but with no perceptible 

 neck ; frons flush with the eyes or slightly produced ; face not produced, very short 

 being mainly occupied by the mouth-opening, bare and broad ; jowls very small ; 

 ocelli three. Proboscis withdrawn ; palpi inconspicuous, cylindrical, and bristly at 

 the tip. Eyes bare, usually but not always touching in the male but well separated 

 in the female, and when the eyes touch the facets on more than the upper half 

 are enlarged. Antennae close together at the base ; two basal joints short and 

 very minutely bristly ; third joint elongate but drooping, strap-shaped, and with 

 any style or arista concealed in a depressed pit (fig. 330). 



Thorax rather oblong, being longer than broad, rather flat on the disc but 

 appearing to be rather convex because the head is depressed • j)ubescence practically 

 absent, but the disc of the thorax bears some minute scaly bristles and the pleurae are 

 minutely pubescent ; front part of the mesopleuree with a rather large depression 



* Vide Corrigenda. 



