369 



twigs of trees on which they lay their eggs. It is possible that the 

 flies select these outstanding dead twigs because they are the haunts 

 of many of the spiders that serve as the hosts of the larvae. 



Papers on North American Cyrtidae 



Johnson, C. W. 



'15. Notes on the species of the genus Acrocera. Psyche, 22: 198. 



King, J. L. 



'16. Observations on the life-history of Pterodontia flavipes Gray. 

 Ann. Ent. Soc. Amer., 9: 309-321. (Contains the principal facts 

 regarding the life history of the family, and a complete bibliog- 

 raphy.) 



Malloch, J. R. 



'16. Some additional records of Chironomidae for Illinois and notes 

 on other Illinois Diptera. Bull. 111. State Lab. Nat. Hist., Art. IV, 

 11 : 341-342. 



Melander, A. L. 



'02. Notes on the Acroceridae. Ent. News, 13 : 179. 



Superfamily Asiloidea 



I have grouped together in this superfamily the families Mydaidae, 

 Apioceridae, Asilidae, and Bombyliidae. This arrangement is in ac- 

 cord with that of Brauer but is radically different from that of Osten 

 Sacken and Verrall, both of whom place the families specified in di f- 

 ferent superfamilies. 



SUPERI'AMILY CHARACTERS 



Larva. — Head in Mydaidae and Asilidae with the exposed portion 

 heavily chitinized, the maxillae broad, flattened dorso-ventrally, usual- 

 ly subtriangular when seen from above, the palpi normally distinct; 

 labrum variable in length, generally pointed; mandibles knife-shaped, 

 situated on each side of labrum and moving vertically between it and 

 the maxillae; antennae small, generally difficult to distinguish. Body 

 cylindrical or subcylindrical, segmentation distinct, seldom with sec- 

 ondary divisions, but if these are present there are also distinct loco- 

 motor protuberances on the abdominal segments; thoracic segments 

 each with 2 long hairs on each side of venter. Apical segment some- 

 what variable, rounded in most genera but occasionally with a sharp 

 upper posterior edge or, rarely, with 2 or 3 slightly chitinized pro- 

 jections on upper posterior margin, never with finger-like fleshy 

 processes; prothoracic and anal spiracles distinct, the latter situated 



