136 EOLAND THAXTER ON THE 



therefore received more attention from earlier botanists. Their imperfect or " Isaria " 

 condition is familiar to all entomologists as a pest in breeding cages and puparia; al- 

 though the ascigerous condition is usually of rare occurrence. They attack all orders 

 of hexapod insects, larvae and pupae as well as imagines, and also certain spiders; often 

 producing what is vulgarly known as a "vegetable sprout" several inches in length. 

 A considerable number of American species are recorded; yet, owing to the lack of suffi- 

 ciently well-marked microscopic characters, as well as to the scarcity of good material 

 for study, the group presents many difficulties, as is usual in cases when too great re- 

 liance has been placed upon gross characters as a means of specific distinction. 



In addition to- the groups above mentioned there are several other isolated instances 

 of entomogenous fungi, among which should be mentioned the so-called Botrytis Bas- 

 siana which produces the disease known as Muscardine, so destructive to silk worms in 

 Europe and apparently identical with a similar form occurring in this country. 



Facultative parasites of insects. — In addition to the obligate parasites briefly enumer- 

 ated above, insects are often subject to the attack of numerous small moulds and bacteria 

 which are in no sense peculiar to them, although they may temporarily assume a habit 

 which is practically that of a true parasite, entering the living host and causing its 

 death. It seems also probable that one or two forms which are truly entomogenous are yet 

 saprophytes, as in the case of a certain Cordyceps ( G. armeniaccC) presiunably growing 

 upon the remains of insects in the excrement of insectivorous birds, as well as the 

 members of the genus Basidiobolus hereafter mentioned, which occur upon the excre- 

 ment of frogs and lizards. DeBary has also pointed out that the species of Cordyceps 

 are normally partial saprophytes, since they attain their full development after the death 

 of the host; but whether wholly parasites or saprophytes, or parasites and saprophytes 

 combined, their peculiarity in growing naturally only upon insects or insect remains con- 

 stitutes them entomogenous, in the sense in which I use the term, to the exclusion of 

 such foi-ms as JPenicillium, Asjoergillus, Cladosporium and the like; which, although they 

 may at times not only grow on insects, but become temporarily truly parasitic upon 

 them, are yet found in nature on a great variety of other substances. 



With this brief reference to entomogenous plants in general we may now turn to the 

 consideration in detail of the group which forms the subject of the present paper. 



Entomophthoiieae. 



General characters. — This family at present comprises several genera, the members 

 of which are not all entomogenous, though closely related structurally. "They are dis- 

 tinguished by the production of numerous hyphae of large diameter and fatty contents, 

 which, in the insect forms, ultimately emerge from the host in white masses of charac- 

 teristic appearance and prodiice at their extremities large conidial spores which are vio- 

 lently discharged into the air and propagate the disease. Tlie common house-fly fungus 

 is perhaps the most familiar example of the kind, and no one can have failed to notice 

 the affected flies in autumn or late summer adhering to looking-glasses or window-panes 

 smTounded by a smoky halo of discharged conidia. In addition to these conidia the 

 propagation of the fungus, after long periods of rest, may be provided for by the forma- 



