28 



OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. 



primary but are probably secondary, are reared from the bags. Three 

 of these are Ichneuinonids, viz: (1) Pimpla conquisitor Say (Fig-. 11); (2) 

 Pimpla inquisitor Say, and (3) Eemiteles thyridopterigis Riley (Fig. 12). 



Fig. 12. — Hemiteles thyridopterigis : a, male: b, female; 

 c, sack of bag worm cut open, showing cocoons of parasite, 

 natural size. 



Of these, the last-named is most abundantly bred, and we have always 

 considered it as the most important parasite of the Bag- worm. The 

 past season, however, we have ascertained that three species of the 

 genus Hemiteles, viz: H. utilis, and two uudescribed species, are un- 

 questionably secondary parasites, and this renders it quite likely that 

 H. thyridopterigis may also be secondary, or, in other words, a parasite 

 of one of the true parasites of the Bag- worm. It is a question, how- 

 ever, which only the most careful study, with abundant material, can 

 decide, as the law of unity of habit in the same genus finds many excep- 

 tions in insect life. The other parasites are as follows: (4) Chalcis ovata 

 Say. This parasite is a very general feeder on Lepidopterous larva3, and 

 we have bred it from seven widely different species. (5) SpiJochaJcis 

 wiarice (Riley). This species, while parasitic on Thyridopteryx, is more 

 partial to the large silk-spinning caterpillars, as we have reared it from 

 the cocoons of all of our large native Silk-worms. (6) Pteromalus sp. 

 This uudescribed Chalcid is found very abundantly in the Bags, but 

 may be a secondary parasite. (7) Dinocarsis thyridopterygis Ash mead. 

 This parasite was bred from the Bags in Florida by Mr. William H. 

 Ashmead, who believes it to be parasitic on the eggs. (8) Tacliina sp. 

 We have bred a large bluish Tachinid from the Bags. Its eggs are 

 commonly attached to the Bags externally, near the neck, and the 

 young larvae, on hatching, work their way into the case. They fre- 

 quently fail, however, to reach the Bag-worm. 



