288 THE CANADIAN ENTOMOLOGIST. 



BiBIONIDiî".. 



2. Dilophus sty^ius Say. 



Tepic. — Twelve ^ s and forty-lhree $ s, Nov. One pair in coitu, 

 which verifies my conclusion that the two sexes associated together in my 

 former determination (see No. 2 of Section I) are the same species. The 

 females vary considerabl} in size, some being as small as the larger males. 

 The small linear blackish stigma in the whitish wings of the $ is often 

 nearly or quite obsolete. 



It is worthy of note that, among th'^ specimens sent me of the females 

 of this species, there was inadvertently included a specimen of a black 

 sawfiy, which would easily pass for a Ç Dilophus stygius if not looked at 

 a second time. This sawfly is of the same uniform deep shining black as 

 the 9 stygius^ is of the same size, and has the same black wings of cor- 

 responding shade. I can hardly resist the conclusion that the sawfly 

 mimics the 9 s^ygitis, though for what reason cannot at present be said- 

 The sawfly is a remarkable form, in that it possesses long-branched 

 antennae. Each antenna is split nearly to base into two branches, the 

 stalk or pedicel being short and bare, and the branches hairy. The 

 abdomen of the sawfly is more shining than that of the 9 stygius, but this 

 does not show save on close inspection, while its general form closely 

 approaches that of the 9 stygius abdomen. Of course, the head of the 

 sawfly is totally different from that of the 9 stygius, but this is not con- 

 spicuous on first sight, the effect being lost in the uniform colour 

 resemblance and otherwise close similarity. 



D. stygius is an abundant Mexican species. The length of the body 

 in the 9 does not average over 6 mm. in the present specimens. I 

 believe that the 9 Dilophus identified by Bellardi as orbatus Say (Saggio 

 I, p. 19) was not that species, but stygius Say. My reasons for this 

 opinion are as follows : 



D. stygius was described by Say from Mexico. D. orbatus was 

 described by Say from Pennsylvania, and Osten Sacken has identified as 

 orbatus two sexes of a species collected in Florida by himself. It is very 

 common for a Middle Atlantic Coast species to extend into Florida, but 

 rarely does a northern species extend so far southwest as Southern Mexico. 

 Bellardi's specimens were from Orizaba. I have myself taken in numbers 

 in the outskirts of Oriziba what I believe to be stygius. The males from 

 Florida, which Osten Sacken identifies as orbatus, and which 1 consider 

 to be that species in all probability, are described as having the win^s 



