and Laboratory Methods. 2219 



then began to put out branched filaments in various directions, after the manner 

 of germinating hyphal bodies or conidia (Figs. 128-30). The cause for this 

 second growth cannot be explained unless it be by some change in the amount 

 of moisture in the air. Had not this growth occurred, there is a possibility that 

 resting bodies would have been formed the same as was found in the caterpillars 

 that had been kept for some time. 



Cultures from Conidia. Since I had had so much difficulty in obtaining pure 

 cultures from hyphal bodies, I thought by resorting to the conidia from the cater- 

 pillars that a much larger percentage of pure cultures could be obtained. Cater- 

 pillars were placed in sterile Petri dishes, one caterpillar to a dish, with a few 

 drops of water at either side of the caterpillar, but not touching it. When the 

 conidia began to be thrown upon the cover they were removed with a sterile 

 needle and cultures made from them. Even with these precautions bacteria, 

 yeast and fungous spores were found to be attached to many of the conidia. 

 They probably became attached to the surface of the basidia from the outside of 

 the caterpillar, or were carried from the inside of the body when the hyphae 

 broke through the segments. Something like three hundred plates were made 

 from conidia obtained in this way, and not over one per cent, of them was pure. 



The conidia germinated readily, and the hyphae grew rapidly for a few days 

 (Figs. 32-35), but they did not give as good results as the conidia which were 

 produced from the hyphal bodies grown in agar. There is a possibility that the 

 fungus in the latter case had begun to adapt itself to the medium and become 

 semi-saprophytic. The growth of the hyphae from the conidia was essentially 

 the same as those from the hyphal bodies. A conidium produced one or more 

 hyphae, the contents of the conidium passing into the hypha, leaving the cell 

 wall of the conidium empty. Septa were formed in some of the hyphae in about 

 fifteen hours after the conidia germinated. The hyphee from the conidia obtained 

 directly from the caterpillars were for the most part simple, and but one hypha 

 from a conidium (Figs. 32-35), while those from the hyphal bodies grown in 

 agar were either simple or branched, and with one or more hyphae from a coni- 

 dium (Figs. 36, 37, 38), indicating that a mycelium may be formed in the body 

 of the host. The difference in the amount of branching can probably be attrib- 

 uted to the difference in the age and not to any essential difference in the 

 conidia themselves. 



It will be necessary to experiment with media of different compositions before 

 one is obtained that is suited to the best development of the fungus, or else 

 the fungus must be able to gradually adapt itself to some standard medium 

 before it can be grown with anything like success and in any considerable quan- 

 tity, in a medium more closely resembling the contents of the body cavity of 

 insects, one containing the essentials of muscle and fat. A bouillon-glycerin 

 medium is being tried for cultures of Empusa from the house f^y. Sufficient 

 work has not yet been done to test it thoroughly. 



Now that it has been demonstrated that Empusa can be grown artificially, 

 . the next thing to determine will be what the proper medium is and the condi- 

 tions under which it grows best. No economic importance can be attached to 

 it for the destruction of grasshoppers or other noxious insects, more than what 



