114 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



Ero tho 

 racica. 



Fig. 110. Cocoon 

 of Argyrodes 

 trigonura. X2. 



Ero thoracica, a spider common to Europe and America, weaves a 

 small flossy cocoon, containing about twelve eggs, which it suspends to 

 various objects, grass, twigs, etc., by a long thread. (See Fig. 

 111.) Emerton has found this spider in New England ; it is 

 common in winter under leaves; he has also seen cocoons like 

 those of the European Ero as above described, but has not identified them 

 with the American species, whose web he has not seen. 



Something similar to this, but a little more complicated 

 in structure, is the pretty orange brown cocoon of Theridium 

 frondeum, which is found suspended ordinarily to a stretched, 

 stiffened cord among rocks or leaves. It appears jiarticularly 

 to love shady positions; at all events, I have found it most 

 frequently among rocks on banks of streams, in ravines, or 

 moist and secluded spots, as far west as the hills of Eastern 

 Ohio. It is about an eighth of an inch long, but varies some- 

 what in length. 



On opening this pretty little cocoon of Theridium frondeum, 

 it is found to be filled with a delicate white silken floss, in 

 the midst of which the eggs are deposited and the young will be found 

 after hatching. The number of eggs appears to differ a good deal. I 

 have counted as many as twenty-five in one cocoon, but many less than 

 this in others. The flossy padding is compacted well towards the top of 

 the cocoon, and passes out of a round opening therein in the shape of a 

 carded cord of straight lines of white silk, which gradually diminishes 

 until it is comj^acted into the stiff white cord by which the 

 whole is suspended. A curious arrangement is shown in the en- 

 larged figure of a dissected cocoon (Fig. 113), which is used by 

 the spider as a cap to the open top of her cocoon. In other words, the 

 cocoon, instead of being a continuous piece of spinningwork 

 gradually tapering into a point, as it appears at the first 

 careless glance, proves to be composed of two pieces. First 

 is the principal part or sac, which has already been referred 

 to as having a round opening at the summit. Fitted di- 

 rectly upon this, but easily separated from it by pulling, is 

 a conical cap, which surrounds the lower part of the sus- 

 pensory cord already described. This cap, by manipulation 

 under the microscope, can be unraveled so that it is seen 

 to have been formed by lapping the yellowish cocooning 

 thread, of which the main sac has been woven, around and 

 around the base of the suspensory cord, after that has been 

 spun. (See Fig. 114.) The whole cocoon forms a very beau- 

 tiful and delicate bit of spinningwork, and shows considerable deftness 

 in weaving on the part of its little architect. 



Somewhat similar to this is the cocoon of Ero variegata (Theridium 



Cocoon 

 Structure 



J 



FIG. 111. Cocoon 

 of Ero thoracica, 

 slightly enlarged. 

 (After Cambridge.) 



