152 PROCEEDINGS OF THE ACADEMY OF [1884, 



these Mr. Webster had bred a parasitic ichneumon-fly. One box, 

 in which mud-balls had been placed the preceding summer, was 

 found by him in the autumn (November) to contain such para- 

 sites together with a number of young spiders, all dead. The 

 spiders were not preserved, but the mud-balls were sent to the 

 S|jeaker for determination. One of these had an opening in the 

 side about one millimetre in diameter from which evidently an 

 ichneumon parasite had escaped. It contained the stiff, white 

 cell commonly spun by the larva of this insect. The other 

 resembled closely the spherical mud egg-nest of the wasp 

 Eumenes, there being even a small nozzle at one pole, from which, 

 however, unlike the mud-daub of the wasp, a slight silken cord 

 protruded. Dr. McCook was much puzzled to decide upon the 

 nature of these objects, but on the wliole believed them to be the 

 work of some hymenopterous insect, and not of a spider. Two 

 ichneumons, which emerged from similar cells, were determined 

 by Mr. E. T. Cresson to be Pezomachus meabilis Cresson. 



Subsequently Mr. Webster sent other specimens, some of which 

 were opened. They contained silken sacks imbedded in the centre 

 of the mud-ball, apparently of spider spinning-work, and within 

 these were fifteen or tv/enty yellowish eggs, evidently of a spider. 

 This, of course, modified the speaker's view, and he set aside the 

 specimens, of which he had now a number, in the hope of hatching 

 out the contents. The disjecta membra of two adult spiders 

 taken near the balls, though much broken, enabled him to deter- 

 mine them as Drassids (Drassoidas, a family of the Tubeweavers), 

 and probably of the genus 3Iico,ria. Mr. Webster simply found 

 these near the mud-balls, but did not know that they had anj'^ 

 connection with them. Dr. McCook moistened the cocoons in 

 order to give a natural condition more favorable for the escape 

 of the spiderlings. should they hatch, and May 30, 1884, on 

 opening a box, he found about thirty lively young spiders 

 therein. On the bottom of the box was a dead ichneumon, wliich 

 had cut its way out of the side of one of the balls, by a round 

 hole. The spiderlings seemed to have escaped from their ball 

 along the slight duct left at the point where the bit of silken 

 cord was imbedded in the hard earth, and thence protruded, 

 forming the cocoon-stalk by which the ball was attached to an 

 undersurface. • The appearance of the spiderlings indicated that 

 they had been hatched two or three days when first seen. They 

 were Drassids, evidently the same species as the broken speci- 

 mens above alluded to. Thus the interesting habit of concealing 

 her future progeny within a globular cradle of mud was demon- 

 strated to belong to a spider, as well, as to a wasp. That this 

 particular species is much subject to the attacks of hj^menopterous 

 parasites is already proved ; but that it is more exposed than 

 many other species which spin silken cocoons otherwise unpro- 

 tected in the very same locality, does not appear. There is no 

 evidence that so strange a habit has developed from necessity, 



