56 8 BIOLOGY OF CHALCIDIDiE — HOWARD. 



THE INSECTS AND STAGES OF INSECTS INFESTED BY CHALCIDIDS. 



Kepresentatives of all of the origiual Liuiiajan orders of insects are 

 parasitized in one or another of their stages by species of this family. 

 Of the fifteen orders of Brauer, forms of but seven are infested by 

 chalcidids, and these are the seven Linnfean orders in their restricted 

 sense. Neither Thysanura, Epliemeroptera, Odonata, Plecoptera, Pla- 

 typtera, Dermaptera, Thysanoptera, nor Mecoptera have ever been proven 

 to be parasitized, largely from the fact that the larger number are 

 aquatic in their early stages,* while most of the land forms are exces- 

 sively minute, but, of course, the vast majority of insects belong to the 

 older and more important orders. The most extensively parasitized 

 orders are Lepidoptera, Hymenoptera and Hemiptera-Homoptera. 



Lepidopterous insects in all stages are infested. The minute chal- 

 cidids of the genus Trichogramma, apparently few in number of species, 

 but enormously abundant in individuals, attack the eggs of Ehopalo- 

 cera, bombycids, noctuids, geometrids, and tortricids, and probably of 

 members of other families. So numerous are these tiny creatures at 

 times that hundreds of thousands of eggs of ii)jurious noctuids are de- 

 stroyed by them, and so small are they that twentj' will develop in a 

 single Qgg of Papilio turnus, the entire contents of which will not ex- 

 ceed 1.5 cubic millimeters. Reverting again to the numbers of indi- 

 viduals, Hubbard found in 1880 that Trichogramma pretiosa, alone and 

 unaided, almost annihilated the fifth brood of the cotton worm {Aletia 

 xylina) in Florida, fully 90 per cent of the eggs of this most abundant 

 and prolific noctuid having been infested. (Fourth Report U. S. Ent. 

 Com., p. 103.) It is interesting to note that these little egg-parasites, 

 although so very abundant in this country, seem comparatively rare in 

 Europe, although the family and its different genera were originally 

 founded on European material. They seldom occur in the European 

 lists, and a few years ago Dr. Gustav Mayr wrote me asking for a 

 specimen of Trichogramma^ saying that he had never seen one! 



The eggs of some of the larger Lepidoptera are also parasitized by 

 species of the genus Eupelmus. Prof. Riley, for instance, has reared 

 species of this genus from eggs of Anthera'a pernyi, Telea pohqyJtemvs, 

 Saturnia io, Datana ministra, and of a s[)bingid on cherry, probably 

 Smerintlms my ops. 



The larva* of Lepidoptera are more extensively parasitized than per- 

 haps any other group of insects. Among the Ch.ilcidid;e representa- 

 tives of eleven of the twenty subfamilies affect lepidopterous larviie. 

 Certain forms attack them when young, others when half grown, and 



* Hymenopteroas parasites of aquatic insects are excessively rare. Agriott/pas 

 cn-matns. an ichneunionid, has been j)roven by Westwood to be a parasite of the cad- 

 dis-fly, Aspatherinm piciconie, and one oftlie Ephydras of our alkaline western lakes 

 is attacked by a chalcid, possibly, however, after the puparia are washed up upon 

 the banks. Moreover, in Europe the egofs of Agr'ion, one of the dragon-flies, are said 

 to be parasited by a species of the inymarid genus Poltjnema. 



