34 B. C. ENTOMULUGICAL PROCEEDINGS, 1912. 



the woolly alder aphis, is a well Itnown species. In the Coleoptera the 

 chief predaceous families are the Coccincllidae, the Carabidae, and the 

 Cicindelidae. In the Diptera many species of Tachina flies are useful 

 parasites, while numerous species of Syrphidae are predaceous on aphides. 

 The order Hymenoptcra probably contains more parasitic forms than 

 all others, members of the orders Ichneumonidae, Braconidae, Chalcidae, 

 Proctotrupidae and others taking part in this useful work. 



Any stage in the life of the host insect may be attacked. Among 

 the parasites of most service to man, those which attack the egg are not 

 the least important. Hubbard, in 1880, found that a minute parasite, 

 Trichogrammii pretiosa, alone and unaided, almost annihilated the fifth 

 brood of the cotton worm in Florida, 90% of the eggs being attacked. 

 A tiny Proctotrupid, Telenomus orgyae, has been reared from the eggs 

 of the White-marked Tussock Moth and Telenomi are known to attack 

 the eggs of fourteen species of Lepidoptera in America. The elm leaf 

 beetle which for several years had proved a serious pest to the elms in 

 the vicinity of Paris, was in one season almost wiped out by an egg 

 parasite, Tetrastichus xanthomelaenaf. Numerous egg parasites of the 

 Gypsy and Brown Tail have been imported into the Eastern States and 

 have there become established. 



The larval stage is particularly susceptible to attack from parasites. 

 A Braconid Apanteles glomeratus has done good work against the 

 imported cabbage worm, it having been imported from England for that 

 purpose. Another important parasite of the same pest is a chalcis fly, 

 Pteromalus puparum. The larvs of nearly all the leaf eating cater- 

 pillars are attacked by numerous hymenopterous or dipterous parasites. 

 Even when apparently well protected larva are frequently discovered 

 and attacked by their parasites. The larva of the May Beetle 

 {Lachnosterna fusca) feeding under ground upon the roots of grasses 

 is often parasitized by a tiny Scoliid (Tiphia linornata.) 



Though not so numerous as larval parasites, pupal parasites are, 

 nevertheless, frequently found. The Ichneumon, Pimpla conquisitor, is 

 parasitic on several species of Lepidoptera, and is an important pupal 

 parasite of the Tussock Moth. 



The imagoes of injurious insects are subject to attack from numer- 

 ous predaceous forms. 



Take the history of any insect pest over a number of years and 

 it will be found to be one of epidemics alternating with periods of 

 comparative immunity. This is due chiefly to the work of its parasites. 

 As the host insect increases in numbers the parasites also multiply with 

 the greater supply of food, and ultimately succeed in reducing the 

 numbers of their host, sometimes almost to the verge of extermination. 



