388 Phylum Arthropoda 



amounts. It should be added daily from the time of hatching until 

 pupation, in very small amounts at first and then in increasing amounts 

 as the larvae become able to keep the water clear. The amounts needed 

 must be learned by experience. 



When the pupae appear they are removed daily by means of a pipette 

 with a large opening. They are placed in containers exactly like the 

 ones previously described for oviposition. Successful emergence from 

 the pupal stage requires that the surface film of the water be quiet, clean, 

 and free from oils. An example of the extreme susceptibility of pupae to 

 oils is afforded by my discovery at one time that eclosion could not occur 

 in a room containing pigeons. The dandruff or scales from the feathers 

 of these birds which settled from the air upon the surface of the water 

 disturbed the surface tension sufficiently to effect this result. 



The newly-emerged adults may be kept in lantern globe cages placed 

 over petri dishes into which pads of cellucotton have been fitted and 

 then moistened. While adults of C. pipiens and C. jatigans will live and 

 grow in a wide range of temperatures, they thrive best at about 80 ° F. 

 Although they will probably live longer at the lower temperatures used 

 by Boyd for Anopheles, they will live for two months or more at 8o° F. 

 This, of course, is an advantage, since a cool incubator is not required for 

 storing them. The females may be fed upon birds or other experimental 

 animals by allowing them to bite directly through the gauze netting of 

 their cages. Separation of the unengorged from the gorged females may 

 be accomplished by catching them singly by means of a small vial from a 

 catching bag made of netting and provided with a sleeve. I have for 

 some time been anesthetizing them with ether in the globe cages and 

 then separating them quickly by picking them up carefully by the wings 

 or legs with small forceps having very flexible points. If the minimum 

 exposure to ether sufficient for immobilizing them is used they very 

 quickly recover from the anesthesia and show no harm as a result of it. 



When attention is directed to the essential requirements of these 

 species it will be found that they may be grown with ease. Indeed, the 

 simplicity of the task is the chief argument for employing them in many 

 types of experiment. 



Bibliography 



Huff, C. G. 1927. Studies on the infectivity of Plasmodia of birds for mosquitoes, 

 with special reference to the problem of immunity in the mosquito. Amer. J. 

 Hyg. 7:706. 



— — — 1929. Ovulation requirements of Culex pipiens Linn. Biol. Bull. 56:347. 



1929. The effects of selection upon susceptibility to bird malaria in Culex 



pipiens Linn. Ann. Trop. Med. and Paras. 23:427. 



■ 1 93 1. The inheritance of natural immunity to Plasmodium cathemerium in 



two species of Culex. J. Prev. Med. 5:249. 



