CULTURE 



squarely under the thin attached layer of the 

 cocoon. Antennae are folded down the ventral 

 side, and in females they reach to about the 

 posterior end of the thorax; in males, they ex- 

 tend to about the second sternite of the abdo- 

 men. The sexes may be readily separated by 

 observing the long antennae of the males and 

 the prominent sting and sensory gonapophyses of 

 the females. 



At eclosion both males and females are ei- 

 ther mature sexually or almost so; consequently 

 females are certainly virgin only if males are 

 not present. In obtaining virgin females , pupae 

 should be isolated, or great care should be 

 taken to see that no mature wasps are present 

 in the culture. These insects have the habit 

 of crawling back into the cocoons after eclo- 

 sion. For this reason it is important to, see 

 that cocoons are either empty or intact. 



Since virgin females are often necessary in 

 experimental work, methods have been devised 

 for obtaining them in numbers and with a mini- 

 mum of attention. The method that has proved, 

 most successful is also the simplest. Cater- 

 pillars are stung by females of any kind. The 

 females are removed before any eggs are laid. 

 Then about five stung caterpillars are spread 

 out along one side of a shell vial, and the 

 mated female that is to be the mother of the 

 desired virgins is placed in the vial with them. 

 The vial is laid on its side and kept in that 

 position. The female then lays her eggs on the 

 caterpillars, the larvae hatch from them and 

 feed, and when they are ready to pupate, they 

 crawl off the host caterpillars and spin their 

 cocoons on the side of the vial instead of pil- 



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