46 THE CANADIAN ENTOMOLOGIST 



New Mexico and the Sierra Madre of Chihuahua. During a trip 

 across the Sierra Madre of Chihuahua and Sinaloa in August and 

 September, 1900, I made especial search for these forms but found 

 none. A similar search earlier in the season would probably have 

 been successful. These flies are of unusual interest as exhibiting 

 facial and oral characters intermediate between those of the Mega- 

 prosopidae and those of the Oestridae, while their weak macro- 

 chaetae show a further trend toward the latter family. It is pro- 

 bable that they parasitize wood-boring larva?. 



If, as seems very certain, Rutilia and Amphibolia represent 

 an old stock, then uterine development must be of very long 

 standing. Both forms have coiled uterus in which the elongate 

 eggs hatch. Certainly a type without incubating uterus would 

 seem to be the original, and elongate subcylindrical eggs should 

 be the more primitive form. If this is true, we must go well back 

 into the past for the beginnings of the remarkable specialization 

 in reproductive system, eggs and maggots of these flies. These 

 specializations have quite certainly been largely adaptive, and 

 thus we are better prepared to accept their independent origin 

 in several stocks. Ovate, flattened eggs are an adaptation for 

 attachment to surfaces, the larger or macrotype forms being 

 designed for fastening externally to host and the small or microtype 

 forms for fastening to leaf-surfaces to be swallowed by host. Here 

 is extensive adaptation even in size — a specialization to a micro- 

 scopic egg that can be swallowed by leaf-feeding insects without 

 iniury to the contained maggot. This last specialization seems 

 to have arisen independently in several stocks, since these eggs 

 exhibit a wholly unexpected variety of structure, the choria of 

 some being reticulate after a honeycomb pattern, those of others 

 having a pattern of raised arcs or wrinkles, while some have a 

 perfectly smooth and unreticulate chorion, and still others have 

 the chorion finely or coarsely punctured or finely or coarsely set 

 with raised points. 



Pediceled eggs are for attachment to hosts in place of flattened 

 eggs. If neither pedicel nor flatness can be secured, nor viscid 

 secretion for gluing the eggs nor structures for depositing them 

 subcutaneously, then in order to meet the requirements of para- 

 sitism the eggs must be held .in the uterus until the maggots are 



