150 ROLAND THAXTER ON THE 



In my own experience,! have never observed the gernihiation of resting spores in any 

 instance, although I have continued cultivations of them in water for upwards of three 

 months. I have not, however, had an opportunity of adopting the plan suggested by 

 Eidam of cultivating them in nutritive solutions, and a trial of this method might lead 

 to more satisfactory results. A germination of the resting spores of certain species is 

 reported by Nowakowski, Sorokin and Ivrasilstchik; and the first-named author states 

 that such spores placed in water in the autumn gei-minate during the following spring. 

 I have, howevei", seen no account of successful ciiltures of this nature unless it exists 

 in the text of Nowakowski. The descrij)tion given bj' Ki-asilstchik of a species {E. 

 uvella), in which he obtained a germination m four days, seems hardly reconcilable Avith 

 the facts as known in other genera. From analogy with Basidiobolus and Conidiobolus, 

 it is not to be questioned that the resting spores germinate, as in these cases, producing 

 the usual conidia; but whether this has been determined by actual experiment, I am un- 

 able to say. The period of rest before gei-miiiation is probably very variable, and its 

 primary object is, of course, to afford a means of hibernation, or of withstanding simi- 

 lar protracted conditions unfavorable to develoiiment, and of long duration. Although 

 a single season is pi'obal>ly the normal period of this resting state, it has been suggested 

 by Brefeld that it may be extended over more than one season, thus allowing the insect 

 host to i-ecover from the effects of Emjnisa epidemics. 



The causes which induce the formation of ix'sting spores can be explained with as 

 little satisfaction among Empusae as in other similar cases. The observations of Brefeld 

 in his experiments with E. spliaerosjierma Fres. {JE. radicans Bref.), which indicated 

 that their production takes place towards the end of the season, gradually su[)planting 

 the conidial form, are not corroborated by my own experience. This, at least, does not 

 seem to be the course followed in the natural development of the fungus out-of-doors; 

 since the examination of some thousand or more of specimens shows that as a rule the 

 lelative number of individuals of a given species, which contain resting spores, remains 

 about the same from the middle of June to the middle of October. Whether the pro- 

 duction of resting spores bears any relation to the number of ])revious generations of 

 conidia is a matter to be determined only by careful and repeated cultures in different 

 cases. None of the remaining causes usually assigned as inducing zygos])oric forma- 

 tion have any appai-ent iniluence in the present instance. But here also repeated experi- 

 ments in different cases, under known and variable conditions of moisture, temperature 

 and nutrition, are necessary to determine whether variation in these respects seems to 

 have any definite connection with the kind of spores produced. 



The hosts of Empusae include representatives from all the hexapod orders; but among 

 them the Diptera are the greatest sufferers, at least in so far as the numbei- of Eni^JU- 

 sae which prey ujion them is concerned. The Hemiptera come next, followed by the 

 Lepidoptera and Coleoptei-a ; while the Neui-optera, llymenoptera and Oi'thoptera are 

 about equally affected, and are attacked by two or three species, only, in each instance. 

 The liability to infection is shared by both larvae and pupae as well as by imagines, 

 although the latter are most commonly affected. In insects where the larvae and pupae 

 differ but slightly from the imago, both these stages are equally susceptible to the dis- 

 ease. Mr. L. O. IIoAvard has also shown me specimens of E. Grylli that had devel- 



