THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



" per litora spargite museum, 



Naiades, et circim vitreos considite fontes : 

 PoUice virgineo teneros hlc carpite flores : 

 Floribus et pictum, divae, replete canistrum. 

 At vos, o Nymphas Craterides, ite sub undas ; 

 Ite, recurvato variata corallia trunco 

 Vellite muscosis e rupibus, et mihi conchas 

 Ferte, Dck pelagi, et pingui conchylia succo." 



Parthenii Eel. 



No. 67. JANUARY 1843. 



I. — Account of a Species o/' Ichneumon whose Larva is para- 

 sitic on Spiders. By John Blackwall, F.L.S.* 



-Immature spiders of the species Epeira afitriada and 

 Epe'ira cucurbitina, and adults of the species Linyphia minuta 

 and Linyphia pusilla, are frequently Infested by the larva of a 

 small Ichneumon, which feeds upon their juices and ultimately 

 occasions their death. This parasite is always attached to the 

 upper part of the abdomen, near its union with the cephalo- 

 thorax, generally in a transverse but occasionally in a longi- 

 tudinal direction, and, though it proves a source of constant 

 irritation, is secured by its position from every attempt of the 

 spider to displace it. Being apodous, it appears to retain its 

 hold upon its victim solely by the instrumentality of the 

 mouth and of a viscid secretion emitted from its caudal ex- 

 tremity. I never saw more than a single larva on the same 

 individual spider, which, indeed, could not supply sufficient 

 nourishment for two. 



In the earlier stages of its growth this parasite has an ob- 

 long oviform figure, somewhat depressed on the under side ; 

 it is whitish with a faint tinge of yellow extending along the 

 medial line, which seems to be occasioned by the contents of 

 the viscera. At this period of its existence the external co- 

 vering presents a smooth uniform surface ; but when it has 

 completed its moultings and attained its full size, the head 

 becomes visible, the body exhibits thirteen distinct segments, 

 and the prevailing hue is pale greenish yellow. 



* Read at the Mancliestev Meeting of the British Association. 

 ^ Ann. ^ Mag. N. Hist. Vol. xi. " B 



