96 MOSQUITOES OF NORTH AMERICA 



has been acquired or not, and this serves as an index to the systematic position 

 of the form in question. As we have before pointed out, the Sabethini form a 

 separate group from the other mosquitoes. This line is not entirely ancestral, 

 having been derived from the culicid stem at a point near Megarhinus, above 

 Anopheles, Aedeomyia and Uranotccnia. The mouth-parts therefore were origi- 

 nally in a certain state of modification, now still shown in the lowest genera 

 such as Johlotia and Lesticocampa. In these the maxillary palpi are rather 

 large, much more so than in the higher forms, such as Wyeomyia. In the Sabe- 

 thini, the predaceous habit has been twice acquired, in Lesticocampa and in 

 Sabethinus (presumably in Sahetlies also, the larvae of which are unknown). 

 In both cases the maxillas have been modified into organs of prehension, but with 

 essential differences. Lesticocampa is an old predaceous type, profoundly modi- 

 fied, derived from a generalized sabethine form (such as Johlotia). The max- 

 illary palpi are long and distinct, the maxillse bearing semi-jointed appendages, 

 and the mandibles are much modified. SabetJiinus is a recent predaceous 

 t3^e, little modified, derived from a specialized non-predaceous form (such as 

 Wyeomyia) . The maxillary palpi are rudimentary, the maxillae of the general 

 type but bearing teeth and an apical horn, which is not jointed, while the man- 

 dibles are scarcely changed from the usual non-predaceous form. In the Ameri- 

 can Culicini, the predaceous habit has been acquired thrice, in Megarhinus, 

 Psorophora and Lutzia. We do not consider the Anopheles true predaceous 

 forms though some of them have the habit developed to some extent (e. g., 

 Ccelodiazesis harberi), because there is as yet no essential modification of the 

 mouth-parts for this purpose, and the larvae are able to subsist also on a vegetable 

 diet. No doubt the habit indicates the beginning of such a modification, and, if 

 persisted in until it became the only method of feeding, structural modifications 

 would follow. The Anopheles must hold their prey by the mandibles, as no 

 other organs are sufiiciently developed for the purpose. The antennae have 

 already too far degenerated to become functional for the purpose, while the 

 maxillae are of a too primitive flat type. It is necessary for the maxilla to have 

 progressed from this type to the conical form of a species feeding only on par- 

 ticles in suspension in water before its modification into an organ of prehension 

 would be possible. The mouth-brushes are not strongly developed enough to be 

 of service in holding prey. We therefore venture to predict that if any strictly 

 predaceous Anopheles larva exists it will be found to have the mandibles modi- 

 fied into organs of prehension. In the truly predaceous Culicini above men- 

 tioned the mouth-brushes have become organs of prehension. Megarhinus is 

 derived from low on the culicine stem. Its maxillje consequently show a large 

 palpus. They are short and square, the shape being partly, no doubt, ancestral 

 on account of the primitive origin of the genus. The mandibles are not espe- 

 cially noteworthy, the toothed surface being well developed, the hair-fringe 

 slight. The predaceous Psorophora are derived from the lower, non-predaceous 

 Janthinosoma group. The maxillae have regained secondarily the flattened 

 quadrate form but the palpus is still a small rudiment borne upon the body of 

 the maxilla. The modification appears at first sight profound, but is in reality 



