TABLES OF PSOEOPHORA 527 



In the larvae of both subgenera the anal plate surrounds the segment and the ven- 

 tral brush is partly inserted within it. A peculiarity of all the larvae of the genus is 

 that the air-tube is only completely chitinized in the last stage. In the first three 

 stages the air-tube is only chitinized apically while the basal portion is membranous. 



The genus Psorophora is confined to America. It extends throughout the 

 tropics and well into the temperate regions of both continents, especially on the 

 Atlantic side. 



The genus is a well-marked one, but stands on characters other than those 

 originally designated. The more striking species were early taken out of 

 Culex and have been kept separate by all authors except some of the early ones. 

 The genus is a development from Aedes and falls into two subgenera, Psoro- 

 phora and Janthinosoma, on the characters of the larvae. The peculiar spiny 

 eggs are the same in both, and the male genitalia and the other adult characters 

 are of the same type throughout. The larvte of the two groups differ particu- 

 larly in the mouth-parts, but these can not be expected to be an index to rela- 

 tionship, as they are the very parts most profoundly modified in adaptation to 

 habits. The serrate character of the mouth-brushes, which has been used in 

 classification, is repeated in certain species of Aedes and is therefore not diag- 

 nostic. 



The difference in the structure of the claws of the female, has probably no 

 greater significance than indicating a difference in the manner of copulating. 

 Although colorational differences mark off the forms with simple claws, there 

 is nothing in the structure of other parts, of the male genitalia or of the larvae, 

 that would admit of their separation. On the other hand the close relationship 

 is unmistakable. 



The larvae live in temporary pools in the ground, formed by rains. They de- 

 velop with the greatest rapidity, hatching immediately after a rain has filled 

 the hollows where the eggs have been lying, and proceeding with the four larval 

 stages as quickly as possible, sometimes in as many days. 



The eggs are laid singly, on the ground, probably in the dry hollows where 

 water usually collects after rains. They have a spinose covering. This probably 

 preserves them from desiccation while the puddles are dry. It is essential that 

 the development should proceed as rapidly as possible, as these transient puddles 

 often dry up in a few days. Indeed, they often dry so soon as to preclude the 

 development of any adults. A second rain, following the first within a few days, 

 is usually essential to secure a successful brood. The eggs from one brood do 

 not all hatch when submerged the first time, and some of them hatch after every 

 considerable rain. 



The winter, or the dry season, is passed in the egg state. The adults of the 

 larger species are rather severe biters and, owing to their size, can puncture the 

 skin of a man through a considerable thickness of clothing. A number of the 

 smaller species apparently do not attack man but feed upon other warm-blooded 

 animals. We have no observations on their mating habits. 



Tables of the Species, 

 adults, structure and coloration. 



1. Mesonotum with smooth nude areas 2 



Mesonotum entirely scaled 6 



2. Mesonotum with median stripe of golden scales ciliata Fabricius (p. 530) 



Mesonotum without such stripe 3 



3. Legs with prominent outstanding scales 4 



Legs without prominent outstanding scales 5 



4. Tips of the hind femora white; leg-scales fine and dense, dark violet 



sccva Dyar & Knab (p. 536) 

 Tips of hind femora obscure grayish; leg-scales coarsely squamose, iridescent 



cilipes Fabricius (p. 538) 



