194 MOSQUITOES OF NORTH AMEEICA 



that of the Corethrinae. It is evident that the group is an old and fixed one not 

 now undergoing rapid evolution. The palpi are long in both sexes, a generalized 

 character, while the wings are generally spotted, as in the lowest forms. 



The larvffi float at the surface and have not developed a long breathing-tube, 

 being most comparable with the lower forms of the Corethrinae, such as Euco- 

 rethra, and with Dim. They are somewhat specialized for the surface-feeding 

 habit, the head being more completely rotary than in Dixa, while a number of 

 tufts of flattened hairs along the back serve as attachments to the surface film. 

 The adaptations, however, are of no fundamental nature and the whole organi2a- 

 tion is distinctly generalized. The eggs are laid singly, floating on the surface 

 of the water, and are supplied with curious floats, differing greatly in the 

 different species. This is a distinct specialization and is yet in an unstable con- 

 dition, as witnessed by the great specific diversity, so contrary to the state of most 

 of the other structures of the anophelines. The larvje are less specialized than 

 any of those in the preceding groups in regard to their choice of habitat, almost 

 any kind of water serving their purpose. Two species inhabit tree-holes, others 

 the water collected at the leaf -bases of bromeliaceous plants, but these are ex- 

 ceptions and indicate a condition of atavism, since we suppose the ancestor of 

 the mosquitoes to have been a form probably breeding in water held by plants. 

 Tables of the GEaraa*. of the Tbibe CixLiciirL 



ADULTS. 



1. wings with the second marginal cell at least as long as its petiole 3 



Second marginal cell less than half as long as its petiole 2 



2. Proboscis rigid, down curved MegarJiinus Robineau-Desvoidy (iv, p. 927) 



Proboscis flexible, normal Uranotwnia Lynch ArribSlzaga (iv, p. 898) 



3. Scutellum rounded, not lobed 4 



Scutellum distinctly trilobed 5 



4. Mesothoraz elongate, over twice as long as wide 



AnopJieles Meigen (iv, p. 962) 

 Mesothorax rounded, not over twice as long as wide 



Cwlodiazesis Dyar & Knab (iv, p. 1035) 

 6. Antennal joints short and broad in the female, the two terminal joints much 

 broader than the preceding ones in the male 



Aedeomyia Theobald (iv, p. 893) 

 Antennal joints long and slender, at least in the female 6 



6. Second joint of antenna very long, 8 to 14 X 1 in $; ^ antennae unmodified, 



similar to those of the female 15 



Second joint of $ antennas short, less than 6 X 1; (^ antennae modified, the 



joints shortened except the last two 7 



7. Prothoracic lobes approximate Hwmagogus Williston (iv, p. 863) 



Prothoracic lobes well separated 8 



8. Cross-veins tending to lie in line, the posterior separated from the anterior 



by less than its own length; palpi of the male usually club-shaped 



Guiiseta Felt (iU, p. 474) 

 Cross-veins normal, usually widely separated 9 



9. Fourth joint of fore tarsus very short. . . Orthopodomyia Theobald (iv, p. 877) 

 Fourth joint of fore tarsus longer, normal 10 



10. Feet with large empodia Lutzia Theobald (iii, p. 466) 



Feet with small empodia 11 



11. Hind tibial scraper with 0-5 sparsely set teeth; abdomen of the female blunt 



at the tip with short retractile cerci 12 



Hind tibial scraper with 7-12 closely set teeth 13 



12. Abdomen subcylindrlcal or depressed Culex Linnaeus (iii, p. 215) ' 



Abdomen strongly compressed Carrollia Lutz (Iii, p. 461) 



13. Female with tip of abdomen tapering, cerci exserted; male genitalia without 



a process from the inner angle of side-piece 14 



Female with tip of abdomen truncated, cerci concealed; male genitalia with 

 a long rod-like process from the inner angle of side-piece 



Mansonia Blanchard (iii, p. 501) 



