614 MOSQUITOES OF NORTH AMERICA 



inaequales una sat magna alteraque distincte minore, feminae aequales longi- 

 uscuU, infra denticulo acuto muniti" (Rev. Mus. de La Plata, i, 373, 1891). 

 Later, discussing the two genera, he says of Culex : " It is essentially dis- 

 tinguished from Heteronycha by the different structure of the palpi of the 

 females and by its small claws, unarmed and curved in both sexes, while they 

 are longer, slender, less curved and with a sharp tooth beneath in Heteronycha " 

 (1. c, ii, 158, 1891). Again, under CvXex flavipes, we find the following 

 statement : " Its appearance, above all that of the females, does not differ 

 much from what obtains in the type of my genus Heteronycha, but a brief 

 examination of the claws is sufficient to recognize not only its specific diver- 

 sity but also that of its position, for they are very small, arcuate and unarmed 

 in one or the other sex of the true Culex, while in Heteronycha they are 

 unidentate in the males and in the females " (1. c, ii, 159, 1891) . Arribalzaga 

 laid great stress on the male structures and this has obscured the essential 

 data, but it is evident that the one species treated by him under Heteronycha, 

 H. dolosa, has toothed claws in the female and therefore belongs with Aedes. 

 Contrasting the habits of this insect with the form he calls Culex flavipes, he 

 points out that Heteronycha dolosa is essentially a mosquito of the country, 

 while the other is associated with man and abounds in the city of Buenos Aires 

 and other towns. There is good reason to believe that the species Arribalzaga 

 called Culex flavipes is the widely distributed form we treat under the name 

 Culex quinquefasdaius (see volume iii, page 345). 



The larvas present some diversity in habits, although this is not so great 

 as might be expected considering the considerable number of species in the 

 genus. Some species inhabit temporary rain-puddles of a more or less evan- 

 escent character. These larvas are less rapid in their development than those 

 of Psorophora. They may occur in the same puddles with Psorophora, but they 

 also inhabit many other situations. Some species inhabit salt water, the tem- 

 porary pools left by high tides at the back of the beaches along the sea coasts ; 

 others inhabit the pools formed by the melting snows in northern latitudes, and 

 these species have but a single annual generation, which appears in the larval 

 stage very early in spring. These species have a northern range, and it is to 

 this group that the arctic mosquitoes belong. Some, while appearing with the 

 early spring broods, appear also later as a second issue, or irregularly in tempo- 

 rary rain-puddles. These latter do not extend to the extreme north, and it is to 

 this group that the salt water forms belong ; to the southward these intergrade 

 with the following group, which is more numerous in the tropics. These 

 are inhabitants of rain-pools and differ in habits from the northern forms 

 only in that they are not restricted to a single early spring issuance; being 

 inhabitants of southern or tropical localities they continue to breed throughout 

 the year whenever water is supplied by the rains. The last group are inhabitants 

 of hollow trees, in which water collects and stands for a long time. This water 

 is of a dark color and peculiar composition. The species addicted to it have no 

 other habitat in nature, though they take more or less readily to artificial recep- 

 tacles made of wood or fouled by vegetable detritus. These species are few in 

 northern localities, but much more numerous in the tropics. The adults are 

 frequently gaily ornamented. "Stcgomyia " calopus belongs to this group. A 

 few species which breed in the water held by the leaves of certain Bromeliacese 

 may be considered an offshoot from this last group and in accordance they show 

 considerable specialization. 



The eggs are laid singly in places where water is liable to collect. It is prob- 

 able that the eggs are generally deposited in the absence of water, though the 

 locality may be moist. Certainly in the case of the early spring species this must 

 be the case, as the females fly until August, long after their breeding-pools have 



