1-84'- Mr. J. Blackwall on the Structure, Functions y (Economy , 



This common spider, which is widely distributed in Great 

 Britain, frequents shrubs, buildings, and crevices in rocks and 

 walls. It pairs in autumn, and the female constructs a subglo- 

 bose cocoon of soft pale brown silk of a loose texture, measuring 

 J an inch in diameter, in which she deposits 80 or 90 spherical 

 eggs of a brown colour, slightly cemented together in a subglo- 

 bose mass. The cocoon is attached to walls and the inferior 

 surface of stones by a thin covering of whitish web. 1 have ob- 

 served that the female changes her integument five times before 

 she arrives at maturity, once in the cocoon, and four times after 

 quitting it. 



In December 1842 and March 1843 I procured several co- 

 coons of Epeira calophylla comprising larvse of two distinct spe- 

 cies of insects belonging to the family Ichneumonid(S, which fed 

 iipon the ova contained in the cocoons and increased rapidly in 

 size; on being converted into pup^e, the females were observed 

 to have the ovipositor turned over the posterior extremity of the 

 abdomen. In the spring of 1843 both sexes of each species, in 

 the imago or perfect state, issued from the cocoons, which I had 

 placed in closed phials. These insects are very dissimilar in 

 size and colour, and the eggs deposited by each in a single 

 cocoon differ in number inversely as the dimensions of the 

 females which produce them ; occasionally I have noticed the 

 larvse of both species in the same cocoon, but I have never detected 

 them in the cocoons of any other spider, however favourable the 

 circumstances might be as regards time, condition, and locality 

 under which they were examined. 



Epeira calophylla usually employs a radius as a medium of 

 communication between its net and a small tubular cell of white 

 &ilk which constitutes its retreat, instead of spinning a separate 

 line for that purpose ; and this peculiar appropriation, whether 

 the radius be in the plane of the net or whether it be withdrawn 

 from that plane, as is frequently the case, imparts an unfinished 

 appearance to the snare, as it prevents the spider from giving a 

 spiral form to the elastic line on which the viscid globules are 

 disposed, though this is sometimes attempted with a greater or 

 less degree of success. No sooner does the spider arrive at one 

 of the radii adjacent to that in connexion with its cell than it 

 returns, traversing the framework of the snare till it arrives at 

 the adjacent radius on the opposite side, when it retraces its 

 steps, and thus, oscillating between the two, spins a number of 

 curved, viscid lines or arcs of circles diminishing in length from 

 the circumference of the net towards the centre. Lister was 

 well acquainted with this peculiarity, so common in the snare of 

 Epeira calophylla, but has fallen into the error of supposing that 

 it occurs invariably. See his ' Tractatus de Araneis,' p. 48. 



