230 



PSYCHE. 



[March 1892. 



these minute spores that the fungus is 

 so rapidly disseminated throughout a 

 field infested with chinch bugs. These 

 spores, however, soon lose their vitality 

 (spores one month old would no longer 

 germinate in our laboratory) and the 

 fungus must make provision for its self- 

 preservation during protracted periods 

 of weather unfavorable to the develop- 

 ment of conidial spores. 



Culture plates in our laboratory, cov- 

 ered with pure cultures of Sporotrichum 

 planted July 9, show the mycelial 

 branches within the culture medium to 

 be swollen at intervals to a diameter of 

 3.9 to S.S micromillimeters ; the aver- 

 age diameter of the unswollen mycelial 

 branches being about 2.5 micromilli- 

 meters. It seems more than probable 

 that the function of these hyphal bodies 

 is to carry the fungus through the cold 

 of winter or the drought of summer. 

 Experiments have been started in our 

 laboratory to test the germinating power 

 of these bodies, but too late to give the 

 results in this paper. 



Resting spores are also found on the 

 culture plates having a diameter of 20 

 micromillimeters, and a thickness of cell 

 wall of i.S micromillimeters. Similar 

 spores are found in the crushed bodies of 

 chinch bugs covered with Sporotrichum. 

 While it was found that pure cultures 

 of Sporotrichum could easily be ob- 

 tained, repeated attempts to inoculate 

 chinch bugs from these pure cultures 

 were unsuccessful. 



As heretofore stated Empusa aphidis 

 was first noticed in our infection case 

 June 28. Eight or ten bugs were found 



covered with a vigorous growth of this 

 fungus. This disease had probably 

 been sent in from some field where it 

 naturally existed. Empusa continued 

 to multiply in the infection cases and by 

 July j 2th it rivalled Sporotrichum in 

 the number of its victims. Active bugs 

 without external signs of disease in the 

 afternoon would be found hanging to 

 the wheat blades the following morning 

 covered with a vigorous growth of Em- 

 pusa. If the fungus were left undis- 

 turbed it would keep on growing at 

 the expense of the tissues of the bug 

 until nothing were left save bits of the 

 chitinous integument. 



Attempts were made to obtain pure 

 fruiting cultures of Empusa, but without 

 success. At first bugs covered with 

 Empusa were placed on the surface of 

 the culture medium in the hope that the 

 spores would be thrown, as is the habit 

 with this fungus, and the growth of these 

 spores would give a pure culture. The 

 spores were thrown in a ring about the 

 bug to a distance of a quarter of an 

 inch, but a rapid growth of bacteria 

 from the bug broke down the culture 

 medium and the Empusa spores did 

 not develop. 



To keep the bacteria from reaching 

 the medium a cover glass was heated 

 over a Bunsen burner until it became 

 very much convexed. This was then 

 placed on the culture medium, convex 

 side up, and upon this were placed 

 three bugs covered with Empusa. A 

 mycelial growth was obtained in this 

 way uncontaminated with bacteria ; but 

 no spores were produced. We have 



