ENTOMOIMITIIOUEAK OF THE UNITED STATES. 



L39 



The formation of zygospores is also quite peculiar, and always results from the conju- 

 gation of two adjacent cells in the s<tni<' hypha, except in some instances where two co- 

 nidia may conjugate directly. In either case conjugation is preceded by tlx; formation 

 of finger-like processes from cither of the conjugating cells, which, arising opposite each 

 other, are usually closely applied. Conjugation, however, does not take place by means 

 of these processes which, at first sight, would suggest a Jihijnchonema-Wka type; hut by 

 the absorption of the partition wall between the conjugating cells and the direct passage 

 of the contents of one into the other. In this instance, as well as in Conidiobolus, the 

 cell in which the zygospore is to be formed is recognizable before conjugation by its 

 larger size. The function of the finger-like processes above mentioned seems wholly 

 connected with the division of the nuclei which pass into them and become divided in 

 two parts; the upper portion disappearing without becoming a new nucleus while the 

 lower passes as a nucleus into the zygospore. The zygospores are of two varieties: one, 

 larger than the more common form, is very thick walled and covered by a peculiar brown 

 incrustation which renders it opaque; the smaller and more usual variety was made to 

 germinate in nutrient solutions and produced hyphae which developed the characteristic 

 conidia of the species. 



Two genera remain to be mentioned: TaricMum of Cohn and Massospora Peck. The 

 former, as has been several times pointed out by writers on Entomophthoreae, is, with- 

 out doubt, merely the resting stage of some Empusa, the conidia of which are as yet 

 unknown. In Massospora, however, which has not, I believe, been previously referred 

 to the present family, we have a form quite peculiar, the near affinities of which cannot 

 be determined by reason of the absence of any knowledge concerning the formation of 

 its resting spores, or the germination of the multitudinous internal spores which char- 

 acterize the genus. 



With this brief mention of the remaining genera we may now pass to a consideration 

 of the genus Empusa, which, with its subdivisions, includes only entomogenons forms. 

 I have preferred to consider these subdivisions as a whole under Empusa as a matter of 

 convenience, as well as from the fact that I am not at present inclined to believe that 

 they have more than a subgeneric value; but my reasons for this course, as well as for 

 my use of the name Empusa in preference to Entomo-phthora, may be better given here- 

 after Avhen the principal morphological differences in the species have been touched 

 upon. 



The Genus Empusa. 



Infection and production of hyphal bodies. — As has already been mentioned, infection 

 among entomogenous Entomophthoreae results from contact with a conidial spore which, 

 adhering to the insect host, enters its body by means of a hypha of germination. The 

 exact method of this entrance is hardly a subject for actual observation unless, perhaps, 

 in insects which, like many aphides; are semitransparent, and, owing to their soft integu- 

 ment, afford an easy entrance to the hypha at almost any portion of the body. In other 

 insects, more especially beetles, grasshoppers, ichneumons and the like, the horny integ- 

 ument must diminish considerably the chances of infection; and in such cases the stig- 

 mata or the thin membrane connecting the body segments and leg joints must be the 



