Culicidae 379 



For both A . quadrimaculatus and A . punctipennis an alkaline reaction 

 is required. For A. crucians, the hay infusion pans have been used while 

 in the acid phase, and later employed for the other species. The acid 

 phase may be prolonged by the addition of small amounts of sugar from 

 time to time. 



To start a new rearing pan, approximately 250-300 larvae, with the 

 larger stages predominating, are transferred to the infusion by means of 

 a teaspoon or a pipette. It is imperative that the larger larvae pre- 

 ponderate, in order that they may consume any surface pellicle as it 

 forms, thereby preventing undue mortality among the smaller larvae. 

 Our experience indicates that it becomes necessary at times, to vary the 

 number of larvae from the normal limits for a few days in individual pans 

 to maintain a balance between food production and consumption. There 

 is no criterion that may be given, whereby an inexperienced person would 

 be justified in increasing or decreasing the number. This is a matter 

 of experience. 



Pans are operated to contribute a quota of pupae daily. If 250-300 

 larvae are maintained, 20-25 pupae will be furnished daily by each pan. 

 The places vacated by the pupae are filled by adding about 50% more 

 small larvae than the number of pupae removed, which is done to offset 

 the mortality. 



The food supplied by the infusion does not appear to be wholly ade- 

 quate for satisfactory development. Hence in order to obtain imagines of 

 maximum size, it is still found advantageous to supplement the diet with 

 Fleishmann's yeast. The yeast is placed on a glass slide which is floated 

 about %-inch below the surface of the water by means of a cork float. 

 The amount of yeast to be placed upon the slide must be determined by 

 the rapidity with which it is devoured. Experience indicates that best 

 results are obtained when moderate amounts are used and renewed several 

 times each day if necessary. The glass slide and float should be washed 

 daily to remove the old yeast cells adhering. 



It is found desirable to employ some type of floatage to secure uniform 

 distribution of the larvae in the pans. This reduces the opportunity for 

 cannibalism and serves to equalize feeding opportunities. Chaff is 

 scattered over the surface or several paraffined sticks or cork strips may 

 be floated on the surface. 



As transformation into pupae takes place, they are removed daily with 

 a pipette to an eclosion pan of tap water. Some type of floatage must be 

 used on the water surface of this pan to keep the pupae spaced apart. If 

 this is not done they tend to collect around the edge, where they nervously 

 bump into one another and jeopardize the safety of those emerging. 

 Broken hay, chaff, or ground cork may be used for floatage. The floatage 

 also aids the emerging adults by providing support for the tarsi and 



