338 



SCIENCE. 



[Vol. XX. No. 515 



one to five in number, being nailed horizontally to them. In 

 this case, the uncultivated or ungrazed margin is greatly re- 

 duced, but even this form of fence offers some protection to 

 various species of insects. Any one who will observe the num- 

 ber of cocoons and eggs that are ensconced betweeu the boards 

 and posts, where these come in contact, will be astonished at 

 their number, especially if his examinations be made during late 

 autumn or winter. 



The minimum protection is probably afforded by a fence con- 

 structed of posts and wire. The vegetation can be grazed off or 

 otherwise removed, reducing the protection thus afforded to the 

 least possible amount, and the wires offer no hiding-place where 

 they are attached to the posts. It is this form of fence that is, to 

 a very large extent, displacing all others except the stone-wall, 

 especially throughout the area above mentioned, and this change 

 materially reduces the protection before offered a considerable 

 number of injurious insects. Of the species thus more or less 

 fostered may be cited the chinch bug, Blissus leucopterus Say, 

 which passes the winter protected by the thick covering of leaves 

 and matted grass. The army worm, Leueania unipuncta Haw., 

 often originates in such places in abundance. A large portion of 

 the larvae of the Stalk Borer, Hydreecia nitela Cauen, pass the 

 «arly part of their larval stage in the stems of grass growing in 

 such localities. Grasshoppers breed there in abundance. The 

 Fall Web-worm, Hypantria cunea Drury, delights to pass its 

 adolescent stage in the crevices about rail and board fences and 

 stone-walls. If, as is often the case, the border of fields along 

 the line of and in the corners of such fences, is allowed to grow 

 tip in a wilderness of blackberry and raspberry bushes, these will 

 harbor the Root-borer, Bembecia marginata Harris, the Rasp- 

 berry Saw-fly. SelandriarubiHurv., and the author of the Gouty 

 gall of the raspberry, Agnlus ruficollis Fab. The Tarnished 

 Plant-bug, Lygus pratensis Linn., will pass its winters in com- 

 fort among the leaves of mullein which adorn such places, and 

 which constitute a veritable nursery for these and other injurious 

 insects, from which they readily spread to adjoining gardens, 

 orchards, and fields. 



Soon after the adoption of barbed wire as a fence material, it 

 ■was discovered that domestic animals were more or less liable to 

 injury from the barbs. This led to a modification, to the extent 

 of placing one board horizontally above the wires, and, while done 

 especially for the protection of animals, it has an entomological 

 and botanical signification which was wholly unlocked for, even 

 by the entomologist or botanist. 



The fall brood of the larvas of Spilosoma virginica Fabr., famil- 

 iarly known as the Common Yellow Bear, reaches maturity in 

 September and early October, and appears to then acquire a some- 

 what nomadic habit of life, possibly being in search of a suitable 

 place for cocooning. In their travels they seem to take advan- 

 tage 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 impas- 

 sable for these caterpillars, on account of the difficulty of crawl- 

 ing 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 larvee, and they 

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

 as with mankind, disaster overtakes them in the midst of pros- 

 perity. This fall brood of larvas seems especially liable to attack 

 from a fungous disease, Empusa aulicm Reich, as determined for 

 cne by Dr. Thaxter, of Harvard University. A caterpillar when 

 affected by this Empusa becomes first paralyzed and limp, but 

 later it is rigid and attached so tenaciously to the board that it 

 only disappears by becoming disintegrated 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 

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

 row path and adding to the danger for other travellers. You can 



readily see that in a short time the narrow way will become so 

 filled with dead that to travel for any distance along this high- 

 way without contracting this fungoid disease is almost an impos- 

 sibility. In proof of this, tbe upper edge of this board, where it is 

 used, becomes literally strewn with corpses. In a distance of 

 forty-eight feet I recently counted seventeen dead caterpillars, 

 and clustered on the surface of the upper end of a post, compris- 

 ing an area of two by six inches, six bodies were observed. As 

 these caterpillars are not gregarious, and being general feeders, 

 their chances of being reached by the spores of Empusa is com- 

 paratively small unless they rub against a diseased larva, or 

 come within a cei'tain radius of such a one when the spores are 

 thrown off or " shot," as it is termed. Hence, as now appears, 

 this mortality is largely due to the cause indicated, and which 

 seems to be a powerful agent in holding the species in check. 



It may be suggested that these larvae might have been attacked 

 before they made their way to the fences, as it is, I believe, a 

 characteristic of Empusa that its hosts seek high objects, and 

 crawl up as far as possible before dying. In my own observation, 

 while this has proved true in the majority of cases, affected in- 

 sects have been observed to travel about but little after reaching 

 sucii elevation. Furthermore, these caterpillars have been ob 

 served in abundance crawling along fences when Empusa did 

 not appear to be present. 



WATCHING A SNAKE FOR AN HOUR. 



BY WAiDO DENNIS. 



One bright morning in July I was walking in the woods, when 

 a snake crossed my path only a few feet in front of me. It was 

 about two feet long, and its dark blotches made it resemble a 

 water snake. It had not been disturbed by my presence, as it 

 moved very slowly, and this slow movement led me to watch it. 



It scarcely crossed the path before it began to ascend a medium- 

 sized dogwood tree (Coi'nus Florida). This to me was a coveted 

 opportunity. The story of an eye-witness as to how a blacksnake 

 had climbed the naked comer of a house to a height of ten feet 

 had left me curious to see something of the kind myself. 



The dogwood tree, near the ground, was about seven inches in 

 diameter, and was a rather smooth-barked one. The tree leaned 

 but slightly for about ten feet of its height, but then it curved 

 sharply to a horizontal, making the highest part of the body 

 about fifteen feet from the ground. The snake started up on the 

 under side of the slant, and apparently found no more trouble 

 going up the tree than it had in going over the ground. It made 

 no effort to wind itself around the tree nor to hug the tree by 

 winding back and forth, as the blacksnake had been reported to 

 do on the corner of the house. It went straight up without crook 

 or turn. 



After ascending about three feet, it seemed to feel its hold 

 weaken, and threw its body into folds. But this was only for a 

 few inches of its course, and it found no occasion to repeat even 

 this expedient. The very acute angles of two or three of the 

 folds, however, showed how well this could be done when neces- 

 sary. When such a protuberance as a knot came in its way, it 

 seemed to care very little for its advantage, and left it to on© 

 side. 



After getting up four or five feet, it stopped ; being anxious 

 that it should go on up, and fearing it would come down, I touched 

 it with a stick, whereupon it moved faster, gliding quickly out of 

 my reach, showing thus that it had been going so slowly from 

 choice, and not from any difficulty in going faster. When it was 

 about eight feet high it stopped again, which made me have re- 

 course to a larger stick. When it had reached the highest point 

 from the ground, I shook the tree, as well as one could a tree of 

 such size, to see if it could keep its hold. This it did, only lifting 

 up its head and poking it out from the tree, where it lay, four or 

 five inches, as if to see what was the matter. It occurred to me 

 to wonder how it would manage its descent, so I left off experi- 

 menting in this line and retired to watch. 



I had to wait but a few minutes before the snake began to turn 

 round by doubling on itself. But after crawling along toward 



