PARASITES OF SPIDERS AND THEIR EGGS. 



From the above examples of life history, which are fairly characteristic, /c";- . 

 one may get the following summary of habits, which, while open to correc- 

 tion at some points, is substantially accurate : 1 . The parasite mother passes V/- \ 

 from point to point in search of a suitable host with a rapid, jerky, intense Vo^J^va, 



action ; 2. discovering her victim she deposits an egg upon the 

 Sum- abdomen, 3. and in so doing she will creep along the lines of 

 H bit spinningwork to the point where the spider is suspended. 4. When 

 near her victim she backs down thereto and deposits but one egg 

 upon each host, which is placed upon the abdomen close to the cephalothorax. 

 5. In about two days the egg hatches into a footless, white larva, which in 

 some cases creeps within the body, probably by some of the natural open- 

 ings, and becomes an internal parasite. 6. The external parasite fastens upon 

 the dorsal base or dorsum of the anterior part of the spider's abdomen, and 

 in two or three daj^s wholly consumes that soft organ, meanwhile growing 

 rapidly, and then begins to spin its cocoon. 7. The cocoon is cylindrical, 

 about six millimetres long and two thick, woven of open and loose white 

 or yellowish silk, and is suspended to the spider's web or other object by 

 a slight band, braced beneath by a similar support. 8. The spinning occu- 

 pies from one to three days, several days are spent in the pupal change, 

 and in about a week the imago appears. 9. It is probable that some larval 

 parasites which are hatched late in the autumn hibernate \vith their hosts. 

 The habits of those parasitic Ichneumonids which infest spider eggs 

 canilot be summarized with even as much satisfaction as the body para- 

 sites, but the following may at least suggest something better. 



Bg-gPara-j^ Soon after the spider mother has laid and enclosed her eggs, 



sitss ' . 



Q ■ and sometimes probably during oviposition, the Ichneumon mother 



inserts her eggs, penetrating the cocoon case when necessary with 



her ovipositor, and leaving a number of eggs or the entire brood within 



a single cocoon. 2. Each egg harbors one parasite, which in certain species^ 



enters it as soon as the larval appetite awakes and entirely destroys it. 



3. In some species it would appear that the larval parasites feed upon the 



eggs indiscriminately, and then spin stiff, close, white cocoons, through 



which the imago gnaws a hole and escapes from the spider cocoon in the 



same way. 4. These parasites are in turn exposed to parasitism from other 



members of the Ichneumonid family.'^ 



VIII. 



Mr. Howard has kindly furnished me a list of known American and 

 European hymenopterous parasites of spiders.* Some of these, together 

 with those heretofore referred to, I have arranged as below, with a view 



' Acoloi'des saitides Howard. ^ See Vol. II., page 395. 



' Since this manuscript was prepared Mr. Howard has published his revised list and 

 my table has been corrected thereby. 



