THE FALL WEB-WORM. 49 
caterpillar. The elasticity or the beak (Fig. 21a) of these bugs 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.” 
FUNGUS 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 reveals 
‘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 after they have made their co- 
coons. Nor 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 fungus has been determined by Mr. Roland Thaxter as Hmpusa grylli, 
21061—Bull 10 1 
