PARASITES OF SPIDEKS AND THEIR EGGS. 61 



then encompassed with a maze of closely intercrossed lines, which to the 

 human judgment seems impenetrable by the mother hymenopter. Yet this 

 cocoon is among those most frequently parasitized. 



Of course, one is always at liberty to offer as explanation the suggestion 

 that this very exposure to attack has, in the struggle for survival, produced 

 the evolution of the more perfectly armored cocoons. In short. 

 Effect of t^hgi-g i^jjs ijggj^ a^ conflict between the mother aranead and the 

 for Sur-'' i^otl^^i' hymenopter, something like that between defensive plate 

 vival. armor on battle ships and offensive projectiles. The difficulty 

 with such an explanation is to establish a point of contact be- 

 tween mother, offspring, and the facts of life from which to postulate con- 

 ceivable interaction and reaction. The theory craves an available pou sto. 

 The danger, if apprehended at all, would only be discerned by the eggs, 

 which are the objects attacked ; moreover, the impression must be conveyed 

 through those eggs within the parasitized cocoon which were fortunate 

 enough to escape destruction. To suppose that the reactionary influence of 

 environment could thus operate through a sensitive egg to a conscious 

 spiderling, and so to the maternal instinct of the adult female, and thus 

 on by heredity, through infinitesimal increments of the protective wards 

 and armor of a silk enswathed or mud daub cocoon, lays a rather heavy 

 burden upon the scientific imagination, even in this heyday age of evolu- 

 tionism. The possibility of cocoon evolution by transmittal through the 

 adult mother need not be considered ; for in the case of the above named 

 species, and most others upon the list, the mother is necessarily eliminated 

 from the problem. In point of fact, she usually dies immediately, or soon 

 after ovipositing and cocooning, and knows nothing of her offspring or 

 their dangers save by anticipative instinct, that foreordination in Nature 

 which is everywhere so manifest in life habits. 



Perhaps one might be permitted to approach the problem from another 

 direction, and suggest that instead of the instinct of the parasitic hymen- 

 opter reacting upon the spider mother to cause increased cocoon safeguards, 

 that instinct simply perceives the well armored cocoon and selects it as 

 the one most secure for her own progeny. 



The cocoon of Agroeca brunnea (see Vol. IL, page 124) is also well 

 devised to preserve the enclosed eggs, and withal is overcoated by the little 

 mother with a plaster of mud, which adds to the protection of armoring 

 that of mimicry. Yet this spider's eggs give hospitality to no less than 

 six parasitic species, showing it to be especially assailable, or at least espe- 

 cially available for such purposes. In this case, however, we can suggest a 

 reason ; for although the spider's cocoon is so well armored, the mode of 

 suspending it (see Figs. 134, 135, Vol. II.) permits the mother parasite to 

 approach it with comparative ease, by crawling along the foot stalk from 

 the plant on which it hangs. Indeed, speaking generally,. one would infer 

 that the cocoons of Tubeweavers and such other species as are placed 



