528 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



among Silk- worms?* both imported and wild, in some of the Eastern 

 States, and that in the fall of 1870 it was so common around Saint 

 Louis that we found hundreds of hairy caterpillars stiffly fastened to 

 their food-plants and covered with the white efflorescence. On sev- 

 eral occasions in Saint Louis we found the Hyphantria larva? gen- 

 erally affected by it. 



The latest authority upon this fungus (Saccardo) gives it as living 

 upon Bombycid larvas, particularly upon the Silk-worm of commerce, 

 in France, Italy, and North America. Botrytis tenella, which he 

 described in his "Fungi Italicce'' as a new species, he noAV considers 

 as only a variety of B. hassiana. This variety is found upon dip- 

 terous larv£e and pupae, upon wasps of the genus Vespa, and upon the 

 larvtb of the coleopterous genus MelolontJia. (P. A. Saccardo, SyU 

 logo Hyphomycetum omnium huscusque cognitorum, Vol. IV, p. 

 Ill), Patavia, ISSG.) 



The first brood of the Web-worms at Washington in 1886 showed 

 in some quite well-defined localities the indications of a fungus dis- 

 ease, which was probably only a variety of this Botrytis. _ It did not 

 become, however, so general as later in the season, when it prevailed 

 everyAvhere; jat it could be observ^ed that the contagion had started 

 from certain points. In such localities almost all the caterpillars were 

 diseased and died, and large numbers of the dead were huddled to- 

 gether as in life. But when investigated their bodies were hard and 

 dry, and would readily crumble to pieces when pressed, producing an 

 odor like that of some mushrooms. Only full-grovv^n, or rather cater- 

 pillars in their last larval skin, were thus affected. Tlie dry remains 

 had retained the original shape, and, if killed but recently by the 

 fungus, their color as well. Before dying the caterpillars had fas- 

 tened themselves very securely to trunks, twigs, and leaves of various 

 trees, somewhat like the common house-fly, that dies by a similar dis- 

 ease in large numbers during September in our houses and produces 

 around itself such a characteristic halo of white spores. Caterpillars 

 infested by the incipient stages of this disease wander about aimlessly 

 and at an irregular speed; often they halt for soine time, then squirm 

 about frantically to start again, and frequently in an opposite direc- 

 tion to the one they were going before. If such a diseased caterpillar 

 is confined to a glass jar and observed, it is soon seen that a white 

 mealy substance gradually grows out of all the soft spaces between 

 the segments, which eventually covers the whole insect, leaving 

 generally only the black head and tips of hairs visible. Before long 

 many spores are scattered about, forming a circle of white dust around 

 the caterpillar, and, if not arrested by an obstruction in its expulsion, 

 the halo thus formed is quite regular and about 2 inches in diameter. 

 Outdoors this white dust is but seldom observed, because even the 

 slightest draft of air will carry it away and drift it about. Even 

 the white mealy substance adhering to the caterpillar itself is usually 

 swept away, and the victims look very much like healthy caterpillars; 

 but they darken with time, and eventually drop to the ground. The 

 magnifying-glass, however, still reveals some spores adhering to the 

 hairs upon'the under side and upon the bark or leaf of the tree in the 

 immediate neighborhood. 



This fungus kills caterpillars even after they have made their 

 cocoons. Nor does the pupa escape. In the latter case the spores 

 form a white crest over every suture of the thoracic segments ; the 

 abdominal segments, however, remain free from it. Evidently the 

 caterpillars were nearly full-grown when attacked by the disease, 



