Culicidae 387 



boiled until almost dry and the water replenished and the boiling con- 

 tinued until the raisins are suspended in their own syrup. These may be 

 kept in a refrigerator in good condition usually until they are all used 

 up. One or two of these large raisins placed on top of the gauze netting 

 of the breeding cage, if moistened each day, will usually not need to be 

 replaced for 4 to 10 days. 



Although it has been shown (Huff, 1929) that females of C. pipiens 

 will ovulate and produce viable eggs upon diets other than blood (such as 

 egg yolk, ox gall, and potato, carrot, and apple juices) as well as the 

 various fraction's of blood, it is advisable to feed them upon living 

 animals if one wishes to use them or their progeny in blood feeding 

 experiments. 



Gravid females require the free surface of water, or completely sat- 

 urated substances such as cellucotton, for oviposition. For maintaining 

 stock I use lantern globe cages placed over crystallizing dishes into 

 which the globes fit snugly (a dish 90 mm. in diameter and 50 mm. deep 

 is required for most makes of globes). For isolation of progenies the 

 females may be placed, one each, in standard-sized bacteriological test 

 tubes Y 3 filled with water and plugged with cotton. Oviposition occurs 

 much earlier and in a larger number of cases when test tubes rather than 

 larger cages are used. The period elapsing between the blood meal and 

 oviposition may also be appreciably shortened by selection of those 

 progenies derived from the eggs earliest laid. 



The feeding and care of the larvae is the most difficult part of the 

 whole technique of caring for these two species. The larvae may be 

 grown satisfactorily in white enameled pans or the square refrigerator 

 dishes which nest one in the other when many different lots must be 

 stored in a small space. Although these mosquitoes normally live in 

 foul water, great care must be exercised to prevent the cultures from 

 becoming too viscous and turbid when grown in the laboratory. This 

 precaution is much more important, too, while the larvae are young. 

 By judging the amount of food carefully it is often possible to rear a 

 brood of larvae to the pupal stage without changing the water. As they 

 grow, the amount of food should be greatly increased. If the pabulum 

 becomes viscous or a surface pellicle forms upon it, the larvae must be 

 transferred to fresh water. This is most conveniently done by pouring 

 the entire contents of the pan upon a piece of fine-meshed bolting silk. 

 The larvae are thus filtered out and may be transferred to the clean 

 water by turning the bolting silk over onto the surface of the water. 

 A variety of substances may be employed as food, such as banana, old 

 protozoan cultures, and dehydrated blood serum, but the one found most 

 satisfactory is dehydrated, skimmed milk. This is available at all times 

 in the same condition and may be administered in carefully graded 



