392 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



measures one-third of an inch in length and one-tenth in diameter. It 

 is of an oblong quadrilateral figure tapering to its extremities, one of 

 which is more pointed than the other. It is lashed to its site by numer- 

 ous fine silken lines. In about one month the perfect insect appears. 

 Blackwall found this parasite on four species of Epeira and two of Liny- 

 phia. 1 The same author figures Hermeteles fasciatus and H. formosus, 

 ichneumon parasites on Agalena brunnea. 2 



A correspondent of "Science Gossip" gives an interesting note with draw- 

 ings of an ichneumon wasp larva that preys upon a small spider in Cey- 

 lon, India. The spider usually attacked is a small black ani- 

 n n la ma ^ w ^h globose abdomen, that spins a loose irregular web on 

 the under surface of leaves. The ichneumon wasp appears to 

 oviposit upon female spiders only, the males being much smaller and 

 unable to support the wasp grub. The egg is fixed to the abdomen of the 

 spider close to its junction with the cephalothorax. The newly hatched 

 larva immediately pierces the skin, and commences to absorb the juices 

 of its host. The spider continues to feed, and re- 

 mains apparently in good health until the parasite 

 is full grown, when the latter destroys its victim, 

 leaving nothing but the empty skin. The larva then 

 commences to spin a flask shaped silken cocoon, at- 

 tached generally to the under side of a cinchona 

 leaf. It builds up the cocoon gradually, complet- 

 FIG. 327. Parasitic larva on j n g. fae walls as it proceeds, forming first a cup 



the body of an India spider. * ' * 



shaped receptacle, which is lengthened by regular 



additions to the open edge, and finally closed. A specimen under observa- 

 tion completed its work in forty-eight hours. 3 



It is an interesting fact, to which Blackwall has called attention, 4 that 

 immature spiders infested by the larva of Polysphincta carbonaria do not 

 change their skins. In what way the parasite can affect the animal thus 

 to cause a suspension of so ordinary a function is not known, but the 

 economy of the fact is apparent. If the moulting were to proceed, the 

 parasitic larva would probably be cast off with the skin and would inevi- 

 tably perish, thus causing a failure of its manifest end in Nature, which is 

 to conserve the life of its kind both directly and indirectly directly by 

 feeding upon the body of the spider, and indirectly by checking the undue 

 increase of that deadly enemy of insect tribes. 



Spiders are also attacked by parasites within the body. A full grown 

 specimen of Epeira cinerea, 5 sent me by Mrs. Treat, had been dropped into 

 alcohol to kill it. Immediately there issued from the abdomen a white 



1 Ann. and Mag. Nat. Hist., Vol. XI., 1843, pages 1 and 2, and Spiders Gt. Br. & Ir., 

 page 352. 2 Spiders Gt. Br. & Ir., pi. xii., A A, B B. 



3 E. Ernest Green, Science Gossip, July, 1888, pages 159, 160. 



4 Ann. and Mag. Nat. Hist., Vol. XI., 1843, page 4. 5 Epeira cavatica Keys. 



