64 



ARTHROPODA 



inches in length. They may be recognized by the division 

 of the under side of the last segment of the abdomen, the 

 attachment of the ovipositor before the tip of the abdo- 

 men, and usually the heavy marginal vein of the front 



wings with a dark 

 spot near its 

 middle. Pimpla 

 inquisitor is a 

 widespread para- 

 site of the tent 

 caterpillar, army 

 worm, tussock 

 moth, and fall 

 web worm. It de- 

 posits from five 

 to ten eggs be- 

 neath the skin of 

 its victim, within 

 which the larvsa feed a few days until they attain adult 

 size. They then emerge and spin their cocoons in a 

 bunch wherein transformation to the adult occurs. 



In the autumn of 1901 fall webworms were so numer- 

 ous in Eastern Pennsylvania that scarcely a tree was to be 

 found that did not harbor from a dozen to a hundred. 

 They crawled over the sidewalks and crept up the houses. 

 In late autumn they formed cocoons of which I collected 

 a large number, and in over ninety per cent of them the 

 insect had been devoured by the larvae of the Pimpla. As 

 a result, the webworms instead of being numerous the 

 following season were very few. 

 A small ichneumon often attacks the large green tomato 



FIG. 50. Pimpla inquisitor, an ichneumon, enlarged 

 about three times. 



