The Ichneumon Flies 



they have spun their cocoons, the latter time being seemingly 

 preferable. When either species is abundant their newly spun 

 cocoons are the rallying points of large numbers of these Pimplas. 

 One of the females after running about for a few seconds will 

 suddenly thrust its ovipositor through the cocoon into the body 

 of the caterpillar which will writhe with pain. The Pimpla, 

 however, will remain apparently undisturbed and push its ovi- 

 positor in to its full extent, remaining motionless in this position 

 for about five minutes during which time the abdomen is slightly 

 moved in a peristaltic manner as if forcing the eggs out and down 

 through the ovipositor. She will then turn round, take a step or 



Fig. 39. — Pimpla inquisitor; b, c, eggs; d, larvae; e, cocoons. 

 (Author's illustration.) 



two, and finally give the caterpillar what is apparently a coup 

 de grace with two or three thrusts in quick succession. Some- 

 times the same operation is repeated. The eggs are not thrust 

 into the body of the caterpillar when the latter is enclosed in its 

 cocoon but sometimes are to be found loose between the cocoon 

 and the caterpillar and sometimes not firmly attached to the skin 

 of the caterpillar standing upright on end. The eggs are elon- 

 gate, somewhat wider at one end than the other, pure white in 

 color and perfectly smooth appearing highly polished. The 

 average length is one mm., and the greatest width about one 



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