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-live to the 

 Tertiary epochs. The Ilymenoptera, Ilomoptera. and Diptera 

 occur only in the Tertiarics; the same is true of the Lepidop- 

 tera. if we exclude the Morris specimen, and of the Coleoptera, 

 with one Triassic exception. The Orthoptera and Myriapods 

 are restricted to the Carboniferous, while the Neuroptera occur 

 both in the Devonian and Carboniferous formations. No fossil 

 Spiders have yet been found in America." (American Nat- 

 uralist, vol. 1, p. G30.) One species of Spider has been found 

 in the Coal-measures of Europe, and a large number in Prus- 

 sian Amber. 



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 cold rains of June and the first part of July, 1865." 



Species of microscopic plants luxuriate in infinitesimal for- 

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

 and certain fungi attack those species which are exposed to 

 dampness, and already enfeebled by other causes. Among the 

 true < ntophyta, or parasitic plants, which do not however ordi- 

 narily occasion the death of their host, Professor Leidy describes 

 Enterobryus elegans, E. spiralis, E. alternates, Arthromitus 

 (T/.s/ctfMs, Cladophytum comatum, and Corynodadus radiatus, 

 which live mostly attached to the mucous walls of the interior 

 of the intestine of Julus marginatus and two other species of 

 Juhis, and Passalus cornutus. Eccrina longa Leidy, lives in 

 Polydesmus Virginiensis ; and E. moniliformis Leidy in P. 

 granvlatus. 



Uut there are parasitic fungi that are large!}' destructive to 

 their hosts. Such are Sphaeria and Isaria. "These fungi 

 grow with great rapidity within the body of the animal tlu-y 

 attack, not only at the expense of the nutritive fluids of the 

 latter, but, after its death, all the interior soft tissues appear 

 6 



