THE CANADIAN ENTOMOLOGIST 55 



Thyllis Erichson. 

 '''The proboscis has nearly the length of the body; it nearly but not quite 

 reaches to the tip of the abdomen. The shield, lying at the base of the 

 proboscis, projects somewhat in the form of a "Halbrinne." The antennae 

 are very small, the first joint exceedingly short, the second pear-shaped, the 

 tip prolonged into a bristle. The pilose eyes are very large, contiguous in the 

 middle line of the head, only that on the front arched side of the head there is a 

 small triangular space for the face, a very small triangle on the vertex and also 

 below the middle, island-like, a small rounded place, on the under side of which, 

 but free from it, are placed the antenna. On the somewhat raised vertex are 

 three inconspicuous ocelli. Behind the eyes the head is considerably prolonged 

 cylindrically. The head is moderately small. The thorax is convex, somewhat 

 bowed or hunch-backed, the dorsal pieces of the prothorax are proportionately 

 large, with the inner corners contiguous, and with the broadened anterior margin 

 encroaching on the hind margin of the head. The separate segments of the 

 abdomen are quite apparent. The wings have a complete submarginal cell, 

 five incomplete posterior cells, of which the first takes in the tip of the wing, 

 and two complete, long, slender discal cells. The body is thinly clothed with 

 fine, short, recumbent, almost silk-like pile. 



Cyrtus, under which genus (Acrocera) Fabricius and Wiedemann placed the 

 one species described by them, is easily separated from these flies by the situation 

 of the antennae. It is more closely related, particularly in the structure of the 

 thorax and the greatly developed prothorax, to Philopota. In venation it is 

 intermediate between the two. In common with Terphis it has the eyes con- 

 tiguous under the insertion of the antennae." 



The following is a translation of Erichson's descriptions of his four species. 



Thyllis crassa. 



Black, red mottled, anterior margin of prothorax, curved lateral meso- 

 thoracic stripes and marginal fasciae of abdomen yellow, costal region of wings 

 fuscous. Length 23/^3^2 lines. 



Acrocera crassa Fab., Syst. Ent., 332,2. 



Cyrtus crassus Wied., Ausser. Zweifl. Ins., II, 15,4. 



Body black, finely cinereous pubescent. Prothorax rufous, anterior margin 

 yellow, lobes on both sides with a median black spot. Mesothoracic dorsum 

 on both sides with a lateral curved yellow stripe bordered rufous, above scutellum 

 twin reddish spots, posterior calli before scutellum with median testaceous 

 stripe; pleura with a reddish spot before insertion of wings. Scutellum with 

 an apical rufous fascia. Abdomen swollen, each segment reddish apically, 

 apical fascia attenuated on both sides, interrupted in the middle, yellow. Legs 

 rufous, fermora blackish, apex yellowish. Wings hyaline, costal vitta before 

 apex marked fuscous. Squamae hyaline. 



Wiedemann described all the markings as yellow, Fabricius pointed out the 

 presence of red at least on incisures of the abdomen. 



Thyllis turgida. 

 Black, marked reddish, outer and posterior margin of prothorax, and lateral 

 mark on mesothorax yellow, wings fuscous hyaline, toward the costa fuscous. 

 Length 4 lines. 



