The Life of Spiders 



surrounded by a thick layer of flossy silk, which in turn is en- 

 closed in the firm, brown, closely woven outer covering that 

 gives the characteristic pear-shaped form to this sac. 



Many egg-sacs are more or less nearly spherical in outline. 

 This is true of some of those that are suspended in the web as 

 is the case with those of the common domestic spider, Tberidion 

 tepidariorum; many others are lenticular in form as for example, 

 the egg-sacs of the Drassids (Fig. 198). While still others depart 

 widely from either of these simple forms. The egg-sac of Miranda 

 aurantia, mentioned above, is pear-shaped; that of the closely 

 allied Metargiope trifaciata is cup-shaped with a flat top; and 

 the egg-sac of Argyrodes irigonum reminds one of a beautiful 

 Grecian vase (Fig. 199). 



The outer covering of most egg-sacs is opaque; but in a few 

 cases it is translucent; the beautiful elliptical egg-sac of the cave 

 spider, Meta menardii, (Fig. 200) does not conceal the enclosed 

 mass of eggs; neither does that of the egg-sac of Aranea trifolium. 



Some spiders after they have completed the silken portion 

 of the egg-sac add a protecting layer of some foreign substance. 

 The grass-spider, Agelcna ncevia, makes its egg-sacs beneath the 

 loose bark of a dead tree, or in some other similar situation, and 

 covers them with bits of rubbish (Fig. 201). A beautiful pear- 

 shaped egg-sac (Fig. 202) which has a complete coating of mud is 

 often found attached by a cord of silk to the lower surface of a 

 stone or a piece of wood lying on the ground. The maker of this 

 mud-coated egg-sac has not been determined as yet. The egg- 

 sacs of Tetragnatha have the appearance of bearing a coating 

 of foreign matter due to the presence of curiously twisted tufts 

 of silk differing in colour from the rest of the egg-sac (Fig. 203). 



Most spiders fasten their egg-sac in some secure position. 

 It is often built against some object as the side of a stone or the 

 branch of a tree or the side of a building. Many are attached to 

 trees beneath the loose bark. The labyrinth-spider (p. 465) 

 fastens its series of egg-sacs to a strong silken cord that holds it 

 in place through the winter, and the species of Miranda anchoi 

 theirs by means of many strong silken threads (Fig. 197). Some 

 species suspend the egg-sac, by a cord, in or near the web. Ir 

 Theridiosoma (Fig. 417) the sac is fastened to twigs or to the sider 

 of cliffs in the damp localities frequented by this spider; this, 

 too, is the case with Ero furcata which envelops its egg-sac in a 



210 



