ENTOMOPHTHOREAE OF THE UNITED STATES. 135 



fected. Of the clifTerciit stages of insects the imaghies, larvae and pupae may all be 

 parasitized, and in some instances a single parasite may attack all these stages in one or 

 more species of the same or different orders; while in others it may confine itself to a 

 single stage or species. 



Entomogenous plants may in a general way be referred to five principal groups: one 

 including the bacterial fomns whicli produce disease in insects; a second represented by 

 certain entophytous algae; and three others all belonging to the fungi proper. 



The first mentioned grouj), represented by the Bacteria, is chiefly of interest from an 

 economic, rather than from a botanical point of view, as the supposed cause of destruc- 

 tive epidemics among useful as well as noxious insects. Instances of this kind ai-e pre- 

 sented by the disease known as ffacherie so destructive to silk worms, and in aftections 

 of a similar nature in other insects, Avhere the "active principle " has, in some cases, 

 been traced to bacterial forms which have been considered sufficiently peculiar to receive 

 distinctive names. The systematic study of the group is necessai-ily one of great diffi- 

 culty, and any opinion as to the validity of specific distinctions in such cases can only 

 be formed by specialists in this department; but from a jjractical standpoint the existence 

 of such aftections promises to afford an important means of defence against noxious in- 

 sects. 



The second group includes a small inimber of peculiar filamentous algae, represented by 

 Enterohryus and its allies, that live attached to the digestive tracts of certain myriapods 

 and coleopterous larvae. They are apparently nearly related to Oscillaria or Beggiatoa 

 among the Protophytes ; but, owing to insufficient observations upon them, their exact af- 

 finities are nnknoAvn. Their habit is probably one of commensalism, rather than of true 

 parasitism; the partially digested food of the host being absorbed directly from the di- 

 gestive traet.^ " 



The fungoid parasites of insects are, as before mentioned, represented by three chief 

 groups : the Entomophthoreae, the Laboulbeniaceae and the entomogenous forms which 

 constitute the l)ulk of the genus Cordyceps. Since the first of these is to receive spe- 

 cial consideration hereafter, it need only be said that its members are closely allied to the 

 Mucorini among the Zj^gomycetes, and are entomogenous with few exceptions. 



The Laboulbeniaceae constitute a small group of very peculiar and minute forms Avhich 

 have been placed by DeBary among the doubtful Ascomycetes. Their parasitism is 

 an external one, which apparentl}^ results in little if any inconvenience to the host; each 

 individual being fixed by a pedicellate attachment to the legs, thorax or other portion of 

 the affected insect. Several genera on Diptera, Coleoptera, etc., are described by Pey- 

 ritsch^ to whom we ai-e principally indebted for our knowledge of the group, although the 

 first genus of the ftimily {^Lahonlh^nkt) was described and figured by Robin.^ The 

 single American representative thus far recorded has been described by Professor Peck 

 as Ap2:)endicularia entomojjhila, n.g. et sp.* 



The pyrenomycetous genus Cordyceps affords by far the most conspicuous examples 

 of entomogenous plants, many of which are of large size, or brightly colored, and have 



' See Leidy, Smiths. Contr. to Knowletlge, v, pp. 1-67 p. 227 (1873) : 72, i, p. 377 (1875), plates. 

 (1853) and Kobiu I. c, p. 395. ^l.c, p. 622, plates. 



' Sltz. d. Akad. wiss. Wieii., 64, i, p. 441 (1871) : 68, i, * Peck, 38tli Report, p. 95, with plate. 



