

THE FALL WEB-WORM. 49 



caterpillar. The elasticity 01 the beak (Fig. 2la) of these bags must be 

 very great; they can bend it in any direction, and yet keep it in suck- 

 ing operation. The poison contained in the beak must act very rapidly, 

 since caterpillars impaled by it squirm but for a very short time, and 

 then become quiet." 



FUNGI'S DISEASES OF THE WEB-WORM. 



''The first brood of these caterpillars showed in some quite well-de- 

 fined localities the indications of a fungus disease.* This did not be- 

 come, however, as general as later in the season, when it prevailed 

 everywhere; yet it could be observed that the contagion had started 

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

 diseased and large numbers of the dead were huddled together 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-grown, or rather caterpillars in 

 their last larval stage, were thus affected. The dry remains had 

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

 their color as well. Before dying the caterpillars had fastened themselves 

 very securely to trunks, twigs, and leaves of various trees, somewhat 

 like the common house-fly, that dies by a similar disease in large num- 

 bers during September in our houses, and produces around itself such 

 a characteristic halo of white spores. Caterpillars infested by the in- 

 cipient stages of this disease wander about aimlessly and at an irregu- 

 lar speed; often they halt for some time, then squirm about frantic- 

 ally to start again, and frequently in an opposite direction 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 their 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 eventu- 

 ally drop to the ground. The magnifying glass, however, still re\ 

 some spores adhering to the hairs, upon the underside, and upon the 

 bark or leaf of the tree in their immediate neighborhood. 



"This fungus kills caterpillars even alter they have made theil 

 coons. Xor does the pupa escape. In the latter case the spores form 

 a white crest over every suture of the thoracic segments ; the abdom- 

 inal segments, however, remain free from it. Evidently the caterpillars 

 were nearly full-grown when attacked by the disease, and possessed 



* This fangus has been determined by Mr. Roland Thaxtei as Empu*a ■■>-i/Ili 



