CULTURE 



their supply of sperm received from the initial 

 mating, or who live for many days afterward. 



The average size of fraternities varies ac- 

 cording to length of life of the mother and the 

 technique of the investigator, being reduced by 

 poor cultural conditions such as small size, 

 scarcity, or disease of the host caterpillars, 

 overcrowding and presence of recessive lethals 

 or semilethals, as well as by crossing between 

 related stocks (close-crossing). Average off- 

 spring per day or per vial may be determined 

 for individual females or for groups of females. 

 The average number of fertilized eggs and hence 

 females per vial or per fraternity may be twice 

 as high in crosses between unrelated stocks' 

 (outcrosses) as in close-crosses. The number 

 of eggs remaining unfertilized and hence the 

 average number of haploid males will be unaf- 

 fected, except for crowding in the larger, out- 

 cross fraternities. 



To facilitate the counting of Habrobracon 

 progeny, it is necessary to etherize and to ex- 

 amine the anaesthetized individuals under a 

 binocular dissecting microscope at about twenty 

 diameters- magnification. " Since Habrobracon is 

 much more resistant to ether than is Drosophila, 

 it is usually safe to allow one group of waspsi 

 to remain in the etherizing bottle while another 

 group is being counted. For anaesthesia two 

 wide mouthed bottles are used. A cork with 

 cotton suspended on a wire and saturated v;ith 

 ether may be transferred from one bottle to the 

 other. One group of wasps is placed in one of 

 these wide mouthed bottles and etherized while 

 those from the other bottle are being counted 

 and examined. After examination the wasps may 



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