THE DISEASES OF INSECTS. 81 



"The species of fossil insects now known from North America, 

 number eighty-one : six of these belong to the Devonian, nine- 

 to the Carboniferous, one to the Triassic, and sixty-tivc to the 

 Tertiary epochs. The Hymenoptera, Ilomoptera, and Diptora 

 occur only in tlie Tertiaries ; the same is true of the Lcpido})- 

 tera, if we exclude the Morris specimen, and of tlie Colcoptora, 

 with one Triassic exception. The Orthoptcra and Myriopods 

 are restricted to the Carboniferous, while the Neuroptera occur 

 both in the Devonian and Carboniferous formations." Mr. 

 Scudder describes from the Carboniferous formation of Nova, 

 Scotia, besides Xylobms sigillarice Daws., four additional spe- 

 cies (X. similis, fractns and Dawsoni, and Archhdus xylohio- 

 ides, n. g. and sp,), forming the family Archhdiclcc. 



The Diseases of Insects have attracted but little atten- 

 tion. They are so far as known mostly the result of the attacks 

 of parasitic plants and animals, though epidemics are known 

 to break out and carry off myriads of insects. Dr. Shimer 

 gives an account of an epidemic among the Chinch bugs, which 

 ••was at its maximum during the moist warm weather that fol- 

 lowed the CvVl rains of June and the first part of July, 1SG5/' 



Species of microscopic plants luxuriate in infinitesimal for- 

 ests within the alimentary canal of some wood-devouring insects, 

 and certain fungi attack those species Avhich are exposed to 

 dampness, and already enfeebled by other causes. Among the 

 true entoYthyta ^ or parasitic plants, whicli do not liowever ordi- 

 narily occasion the death of their host. Professor Leidy describes 

 Enterobryns eJegans^ E. t^j^iraJis, E. alteniatus, Arthromit-iiH 

 rristahis, Cladophytnm comatum^ and CorynocJadns radiafHS, 

 which live mostly- attached to the mucous walls of the interior 

 of the intestine of Jnhis marginatus and two other species of 

 Jtdus, and Passaivs cornidus. Eccrina lovga Leidy, lives in 

 Polydesmns Virgiviensis ; and E. monUiformis Leid}' in P. 

 i/ramdatits. 



But there are parasitic fungi that are largely destructive to 

 their hosts. Such are Spliaeria and Isaria. "-These fungi 

 grow Avith gi-eat rapidity within the body of the animal they 

 attack, not only at the expense of the nutJi^itive fluids of the 

 latter, but, aft^-r its death, all the interiar soft tissues api)ear 



