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, Aédeomyia and Uranotenia. The mouth-parts therefore were origi- 
nally in a certain state of modification, now still shown in the lowest genera 
such as Joblotia 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 Sabethes also, the larve of which are unknown). 
In both cases the maxille 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 Joblotia). The max- 
illary palpi are long and distinct, the maxille bearing semi-jointed appendages, 
and the mandibles are much modified. Sabethinus is a recent predaceous 
type, little modified, derived from a specialized non-predaceous form (such as 
Wyeomyia). The maxillary palpi are rudimentary, the maxille 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., 
Celodiazesis barberi), because there is as yet no essential modification of the 
mouth-parts for this purpose, and the larve 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 sufficiently developed for the purpose. The antenne have 
already too far degenerated to become functional for the purpose, while the 
maxille 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 maxilla 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 maxille 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 
