GENERAL OOCOONING HABITS OF SPIDERS. 129 



yellowish eartli or clay; but balls from Central Illinois are made out of 

 the rich black soil common to the prairies. They vary in diameter from 

 one-half to one-fourth of an inch. (Figs. 147, 148.) From most of them 

 a slight silken cord protrudes (Figs. 147, 148, 153, 154), by which they are 

 often found attached to the under side of a board or stone. The cord is 

 sometimes thickened into a cup shaped patch at the point of attachment, 

 and is occasionally composed of several threads. When these mud balls 

 are softened in water one is able to open them, and in some cases tin- 

 mud peels off in little layers like the skin of an onion, indicating that the 

 method of structure is to plaster a thin coating of mud upon the entire 

 cocoon, and add successive layers, which likewise cover the whole surface 

 before another layer is begun. It is evident that no little mechanical skill 

 is involved in such even distribution of the mortar. 



In the centre of the mud ball is found a cocoon of delicate structure 

 and pure white color (Figs. 151, 152), within which a few eggs are depos- 

 ited. This can be lifted out of its matrix, leaving the round 

 concavity smooth and well defined, as shown at Figs: 149, 150. 



Structure ^ ie stoc ^ ^ * e cocoon * s carried at one point entirely through 

 the mud ball, and issues at the surface in a thin cord wlmsr 

 use has been alluded to above. This stalk or suspensory cord is, of course, 

 spun before the plastering begins, and is covered over gradually, an act 

 which must require delicate manipulation. 



By keeping some of the cocoons in a moist condition, I was able to 

 batch from one, May 30th, a brood of about thirty lively young Drassid 

 spidcrlings. They apparently belong to the genus Micaria, and I therefore 

 named the species Micaria limicume, 1 although with much hesitation, as 

 it is difficult to determine species from young spiders. 



These mud balls in external form closely resemble the spherical mud 

 egg nest of the wasp Eumenes, which I have often found attached to the 

 stalks of weeds, grasses, etc., in the neighborhood of Philadelphia, (Fig. 

 156.) It is certainly interesting to observe that this habit of concealing 

 the future progeny within a globular cradle of mud belongs to a spider 

 as well as to a wasp, and to note how maternal' solicitude finds expression 

 in like forms among widely separated orders. 



Limicunse appears to be much subject to the attacks of hymenopterous 

 parasites. Mr. Webster found parasitic ichneumon flies in some of his 

 boxes, which had evidently crawled out of one of the mud balls. 

 Limicu- g ome o f the balls seen by him had openings in the side about 



nee s 



Par it one millimetre in diameter (Fig. 148), from which evidently 

 the ichneumon had escaped, since it contained the stiff white 

 silken case commonly spun by the larva of this insect. I secured from 

 one of my specimens, in the process of hatching the spiderlings, two of 



1 Proceedings Acad. Nat. Sci., Philadelphia, 1884, page K>:i. 



