ENEMIES AND Til Kill INFLUENCE. 



379 



to the one and inimical to the other, may be seen in tlie nunilxr of ara- 

 neads in that or the succeeding year. This is also true of the alnmdance 

 or lack of a natural food supply. For example, the boat houses, fences, and 

 outbuildings at Atlantic City fairly swarm with Epeiroids, especially Sclop- 

 etaria and Strix. This abundance is probably caused by the presence of 

 greenhead flies with which the district is infested and which, affording 

 an excess of food for the adult and partly grown spiders, relieves them 

 from the necessity of preying upon their own species, whicli tJius increase 

 enormously as compared with sections a little distant. 



But with these and such like exceptions, and notwithstanding all other 

 variations, the distribution of a given orbweaving species in a given sec- 

 tion will be found surprisingly uniform from year to year. Tlie balance 

 of hostile and unfriendly influences is held well poised by Nature's even 

 hand. The enemies of spiders 

 may be divided generally into 

 those which assail the animal 

 itself and those whicli affect 

 its eggs. 



Among the enemies of spi- 

 ders, as of all other creatures, 



may be placed the 

 Season ■, c iv 



~, c|janges oi the sea- 



sons. The araneads' 

 power to endure cold is great, 

 but an unusually cold and 

 moist winter will destroy 

 many. Heavy rains prove fa- 

 tal, especially to the young, 

 and to females great with 

 eggs — beating down the foliage 

 in whicli they are ensconced, or sweeping the creatures themselves to the 

 ground. The extreme tension of the abdominal sac under the distended 

 ovaries makes fatal a shock that otherwise would work little harm. 



It is well known that toads and lizards take kindly to a spider diet. 

 In southern Florida I once found a young lizard, while in the act of 

 shedding its skin, and with the white moult still adliering to it, 

 devouring a large Tetragnatha. (Fig. 321.) Many birds relish 

 spiders and j^ursue tlieni at all seasons, plucking the Sedentary species out 

 of their very webs. In the autumn, when the broods of younglings are all 

 afloat upon their little aerial ships, swallows and swifts, birds that take 

 their prey upon the wing, have been seen skimming the tiny balloonists 

 into their bills as they coursed the air. A specimen shot for examina- 

 tion showed the accuracy of the observation by the presence of spiderlings 

 in the crop. It may be said in brief that all the larger animals with 



Fig. 321. A moulting lizard eating a spider. 



Animals. 



