Observations on Some Entomoplitliorecc. 175 



the wires, and, while done expressly for the protection of the 

 animals, it also took on an entomophthological aspect wholly 

 unexpected by the naturalist. The fall brood of the larvre of 

 Spilosoma virgi7iica P'abr., familiarly known as the Common 

 Yellow Bear, reaches maturity in September and early Octo- 

 ber, and appears to then acquire a somewhat nomadic habit of 

 life, possibly being in search of a suitable place for cocooning. 

 In their travels they seem to take advantage of fences, and 

 convert them into highways, over which they travel in great 

 numbers. Now, with a fence of rails or boards, the travel is 

 distributed over all of these, though the uppermost seems to 

 be preferred. A barbed wire fence is well-nigh impassable 

 for these caterpillars, on account of the difficulty of crawling 

 along the wires and over an occasional barb which stands in 

 the way. The addition of the top board to a fence of barbed 

 wire settles the transportation problem with these larvae, and 

 they crawl along upon the upper edge in great numbers ; but, 

 as with mankind, disaster overtakes them in the midst of 

 prosperit}'. This fall brood of larvae seems especially liable 

 to attack from a fungous disease, Einpusa aidicce Reich., as 

 determined for me by Dr. Thaxter, of Harvard University. 

 A caterpillar, when aflfected by this Empiisa becomes first 

 paralyzed and limp, but later it is rigid and attached so tena- 

 ciously to the board that it only disappears by becoming dis- 

 integrated and washed off by rains. Now, when a caterpillar 

 dies from this cause, it usually becomes firmly affixed right in 

 the way of the migrating larvae, so that one of these can 

 scarce pass in either direction without rubbing against the 

 corpse, as the way is only an inch in width. In thus coming 

 in contact with the dead body of its fellow, in all probability 

 some of the spores of Empusa become attached to its own 

 body and soon do their work, the dead, as before, lying in the 

 narrow path and adding to the danger of other travelers. 

 Now, one can very readily see that in a short time the narrow 

 way will become so filled with dead that to travel for any 

 distance along this highway without contracting this fungoid 

 disease is almost an impossibility. In proof of this, the upper 

 edge of this board, where it is used, becomes literally strewn 

 with corpses. In a distance of forty-eight feet, on a fence of 

 this description, near Wooster, Ohio, in October, 1892, I 



