NATURAL COISTTEOL OF CITEUS MEALYBUG IN FLORIDA. 9 



noted, this stage has been found much less abundantly in Florida 

 than the conidial stage. This is perhaps due to the fact that the 

 insects in which it occurs are invariably small in size, and usually 

 hidden in bark crevices or other situations where their detection is 

 difficult. The method of formation appears to be zygosporic, but a 

 sexual process has never been actually observed. Specimens have 

 occasionally been observed such as that drawn in Plate I, 18, but 

 the exact nature of the association of the hyphal bodies to the resting 

 spores has not been determined. The mature resting spore, how- 

 ever, is invariably provided with a hyaline papilla or protuberance 

 which indicates that a sexual process somewhat like that described 

 by Thaxter in E. fresenii^ to which E. fumosa is in many other re- 

 spects similar, has taken place. It is, in fact, difficult to explain the 

 presence of this protuberance in any other way, for no known type 

 of azygosporic formation produces such an appendage. 



The nature of the factors which in the one instance cause the 

 hyphal bodies to form conidia and in the other instance to form 

 resting spores is incompletely understood. In certain species of En- 

 tomophthora both types are formed simultaneously in and on the 

 same individual, but in E. fumosa they are not associated, diseased 

 insects showing either conidia exclusively or resting spores exclu- 

 sively. In E. pseudococci the writer ^ showed that zygospore forma- 

 tion could be readily induced by placing cultures containing " ma- 

 tured " hyphal bodies in darkness, and it seems probable that the 

 same factor plays a part in the present instance, because, while the 

 fungus was collected at various hours of the day, only mature 

 resting spores were observed. None were seen in the process of 

 formation during daylight hours. In certain other similar fungi, 

 such as Massospora cicadina, the seasonal factor seems also to play 

 a rather definite role. Eesting spores of this form are produced 

 late in the season only, after the conidial formation has ceased. In 

 E. fumosa resting spores were in fact first observed at the time the 

 mealybugs were becoming noticeably less numerous, though the 

 small size and inconsj)icuousness of such infected insects may likewise 

 have been factors preventing an earlier discovery. 



As in many other species of the genus, the resting spores have 

 never been observed to germinate. Failure to secure germination 

 is apparently due to the fact that suitable artificial environmental 

 conditions have never been supplied. In certain species, such as 

 E. pseudococci^ however, a germ tube arises from the resting spore 

 which produces a conidium that is discharged in the usual manner; 

 from analogy, therefore, it is believed that a similar process occurs 

 in the species that have not yet been cultivated artificially. 



» Speare, A. T. Op. cit. 



