200 



ENTOMOLOGY 



the insects, and the dissolved nitrogenous matter is absorbed into the 

 plant. Utricularia has little bladders which entrap small aquatic in- 

 sects. These plants are only partially dependent on insect-food, how- 

 ever, for they all possess chlorophyll. 



Bacteria cause epidemic diseases among insects, as in the flacherie of 

 the silkworm; and fungi of a few groups are specially 

 adapted to develop in the bodies of living insects. 



Those who rear insects know how frequently cater- 

 pillars and other larvae are destroyed by fungi that 

 give the insects a powdered appearance. These fungi, 

 referred to the genus Is aria, are in some cases known 

 to be asexual stages of forms of Cordyceps, which forms 

 appear from the bodies of various larvae, pupae and 

 imagines as long, conspicuous, fructifying sprouts (Fig. 



The chief fungus parasites of insects belong to 

 the large family Entomophthoraceae, represented by 

 the common Empusa muscce (Fig. 252) which affects 

 various flies. In autumn, especially in warm moist 

 weather, the common house fly may often be seen in a 

 dead or dying condition, sticking to a window-pane, its 

 abdomen distended and presenting alternate black and 

 white bands, while around the fly at a little distance 

 is a white powdery ring, or halo. The white interseg- 

 mental bands are made by threads of the fungus just 

 named, and the white halo by countless asexual spores 

 known as conidia, which have been forcibly discharged 

 from the swollen threads that bore them (Fig. 252) by 

 pressure, resulting probably from the absorption of 

 moisture. These spores, ejected in all directions, may 

 infect another fly upon contact and produce a growth 

 of fungus threads, or hyphce, in its body. The fungus 

 may be propagated also by means of resting spores, 

 as found by Thaxter, our authority upon the fungi of insects. 



Empusa aphidis is very common on plant lice and is an important 

 check upon their multiplication. Aphids killed by this fungus are 

 found clinging to their food plant, with the body swollen and discolored. 

 Empusa grylli attacks crickets, grasshoppers, caterpillars and other 

 forms. Curiously enough, grasshoppers affected by this fungus almost 

 always crawl to the top of some plant and die in this conspicuous position. 



FIG. 251. Fruc- 

 tifying sprouts of 

 a fungus, Cordyceps 

 ravenelii, arising 

 from the body of a 

 white grub, Lachno- 

 sterna. Slightly 

 reduced. After 

 RILEY. 



