380 Phylum Arthropoda 



thereby reducing the risk of the adults becoming caught in the surface 

 film. 



It is advisable to change the water in the eclosion pan daily to prevent 

 pellicle formation, which will kill the pupae. This pan is placed beneath 

 a specially built eclosion cage in the form of a screened cone that fits 

 over the edge of the pan. It is kept in a cool dark place in the summer, 

 and in the water bath in the winter. 



Small pupae indicate that the larvae are undernourished. This may 

 arise from either the use of pans with insufficient plankton or from keep- 

 ing too many larvae in a pan. Undersized pupae should be killed, as the 

 imagines they produce will be useless. 



Early attempts at insectary rearing of anophelines indicated that con- 

 siderable space was required for nuptial maneuvering. Mating of indi- 

 viduals recently derived from wild stock did not occur in small cages, 

 and it was not until the imagines were confined in a cage with dimensions 

 of approximately 8 by 10 by 13 feet, that the fertilization of sufficient 

 females was secured. In addition to adequate space, mating also requires 

 that the breeding stock of the colony be composed of large, vigorous 

 imagines. 



A. quadrimaculatus can become well adapted to life in such an artificial 

 environment. Up to the present (June, 1936) the Florida colony has 

 passed through the 48th generation, allowing an average of one genera- 

 tion per month in captivity. This adaptation probably accounts for the 

 successful establishment of a sub-colony in a small cage with screened 

 sides, 30 inches square and 36 inches high. The imagines originally in- 

 troduced were taken from an eclosion cage before mating, about 56 hours 

 after emergence and had just previously been fed, the males on glucose 

 and the females on blood. In the new environment, the colony has al- 

 ready been maintained for several generations. 



The breeding colony requires very little attention other than the estab- 

 lishment of a reliable source for blood meals. This is most satisfactory 

 when furnished from the person of the technician in charge. One of the 

 most important factors in establishing a new colony is to have an attend- 

 ant who will conscientiously endeavor to persuade all the females to feed 

 as often as possible. The males are fed on raisins continuously kept on 

 several small trays, or they may be fed on dextrose solution, which is 

 a satisfactory food. Dead imagines are picked up daily to keep out 

 fungous and bacterial contamination. 



In Florida, density of the colony is maintained at about 5,000 adults 

 in the winter, and decreased to about 3,000 in the summer. This is done 

 because we find that mortality is greater in the winter months, while feed- 

 ing and egg laying are diminished. A ratio of approximately 2 males to 

 1 female is maintained. 



