NATURAL CONTROL OF CITRUS MEALYBUG IN" FLORIDA. 7 



wall bulges out in the direction of least resistance, with the result 

 that asymmetrical, egg-shaped, or even dumb-bell-shaped bodies 

 are formed. They represent the vegetative stage of the fungus, 

 the stage in which the parasite grows at the expense of its host. 

 Such bodies live, so far as can be determined, primarily in the blood, 

 absorbing nourishment therefrom, but after having absorbed the 

 blood, or at least after all of the body fluids have disappeared in 

 diseased mealybugs, other tissues break down and evidently furnish 

 additional food. As they grow they reproduce rapidly by a budding- 

 off process. While at first they apparently impede the blood circu- 

 lation slightly, they later fill up every nook and crevice of the body 

 cavity and must therefore nearly inhibit it. Later the muscles and 

 all other soft tissues are destroyed, leaving only the heavily chitinized 

 structures, until at last the interior of the insect's body is completely 

 and solidly filled. It is at this stage of development, when all liquid 

 matter has been absorbed, that the body cuts like a piece of cheese. 

 This condition marks the end of the vegetative stage. 



All subsequent development of the parasite which takes place 

 after the insect is dead is reproductive. Two types of reproductive 

 bodies are formed, conidia and resting spores, the type depending 

 upon factors that are only in part understood. In certain ^other 

 species they may be formed simultaneously in and on the same in- 

 dividual, though in the present instance resting spores and conidia 

 are not associated in the same specimen. Whichever reproductive 

 body is formed, however, they both arise from the hyphal bodies, 

 which obviously must behave cliiferently in each instance. 



When conidia are to be produced the hyphal bodies send out simple 

 " germ tubes " in the manner shown in Plate I, 20, which bore through 

 the body wall of the host into the open air. Thousands of hyphal 

 bodies produce as many germ tubes, and the latter on the outer sur- 

 face of the insect's body, together with the conidia which are formed 

 at their tips, cause the slate-gray colored wool-like appearance 

 mentioned below. They stand out from the insect's body in much 

 the same manner as the fascicles of hairs extend out from the body 

 of a hairbrush. They swell up at their tips (PI. I, 1) and into the 

 swollen portion flows the entire protoplasmic content of the hyphal 

 body and germ tube. By a process which is characteristic of this 

 group of fungi, the swollen portions are cut off from the germ tube 

 by transverse walls, and the resulting fusiform elliptical conidium 

 is literally shot off from the germ tubes. The force by which this 

 is accomplished is considerable, because the conidia are thrown to 

 a distance of 6 or more millimeters. In some species of Entomoph- 

 thora the conidia are thrown nearly an inch away from^ the body of 

 the infected host. This phenomenon was observed several times 



