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-five to the 

 Tertiary epochs. The Hymenoptera, Ilomoptera, and Diptera 

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

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

 with one Triassic exception. The Orthoptcia and Myriopods 

 are restricted to the Carboniferous, while the Neuroi)tera occur 

 both in the Devonian and Carboniferous formations." Mr 

 Scudder describes from the Carboniferous formation of Xova 

 Scotia, besides Xyhbi^ts sigillarice Daws., four additional spe- 

 cies (X. similis, fractus and Datvsoni, and Archiulus xylohio- 

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



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 c\ VI 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 eyitojihyta, or parasitic plants, which do not however ordi- 

 narily occasion the death of their host. Professor Leidy describes 

 Enterohryna elegans, E. spiralis, E. cdternahis, Arthromitus 

 a-istatus, Cladophytnm coonattim, and Corynodadus radiatvs, 

 which live mostly attached to the mucous walls of the interior 

 of the intestine of Jdlus marginatus and two other species of 

 Jidus, and Passcdus cornutus. Eccrina loiiga Leidy, lives in 

 Polydesmus Virginiensis ; and E. moniliformis Leidy in P. 

 granidcdus. 



But there are parasitic fungi that are largely destructive to 

 their hosts. Such are Sj^haeria and Isaria. "These fungi 

 gi-ow with great rapidity within the body of the animal they 

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

 latter, but, after its death, all the interior soft tissues ai)pear 

 6 



