Jan. 15, 1920 Further Studies of Sorosporella uvella 433 



to be susceptible to the disease. The other species of Lepidoptera — 

 Hyphantria textor, Phlegethontius sexta, and Bombyx mori — did not die 

 of the disease when they were inoculated by the usual methods, yet when 

 conidia were injected into the blood of Phlegethontius sexta and Bombyx 

 mori, by means of a capillary pipette, death followed; and when such 

 insects were examined, it was found that blastocysts had developed in 

 the blood in a normal manner. 



In general, the inoculations were made by one of the three methods 

 outlined below, and after infection the insects were placed in sterile bat- 

 tery jars, partly filled with sterile sand, or if a record of specific insects 

 was desired, they were isolated, one each in small sterile boxes. Control 

 larvae were kept with all experiments. 



DIRECT CONTACT METHOD 



Larvae were placed in flasks or bottles of 500-cc. capacity in which 

 there was a well-developed fruiting surface of the fungus. They were 

 allowed to remain therein for varying periods of time in the several 

 tests and were therefore constantly crawling about over the thallus. 

 It was realized that insects in the field would probably be in contact 

 with the source of infection only for a moment; therefore, in order to 

 simulate in artificial cultures conditions as they occur in the field, the 

 length of time which the insects were allowed to remain in contact with 

 the fungus in the laboratory tests was limited in certain cases to one or 

 two minutes, although in other instances the insects were left in the 

 inoculating flasks for several hours. 



In other experiments bits of the fungus thallus were removed from 

 cultures with a sterile needle and rubbed upon the body of the larvae, 

 or in other instances small portions of the thallus were placed in small 

 boxes on the top of a layer of moist sand and fresh larvae were then 

 inserted into the boxes. The fungus was allowed to remain in such 

 receptacles for several days so that the cutworms were in daily contact 

 with it. 



It is obvious, therefore, that although the methods of inoculation 

 varied in detail, the principle underlying all was the same and consisted 

 in allowing larvae to come in direct contact with the fungus. 



In the discussion of the morphology of the conidia the fact was men- 

 tioned that they cohere after ab junction, indicating that a substance is 

 secreted which renders them viscous. This substance is not secreted as 

 profusely as in certain other verticilliacious Hyphomycetes, however; 

 the little heads of conidia were never observed involved in mucus. It 

 is obvious that a substance of this sort would serve also to fasten the 

 conidia to the bodies of insects with which they came in contact; and 

 if certain of the conidia found lodgment in regions suitable for their 

 further development, it is reasonable to believe that infection would 

 result. It is apparent, however, that when the cutworms were allowed 



