Arachnida. 9737 



distinctive marks of the two sexes in the viviparous lizard ? This is 

 a point on which I should much like information. 



Humphrey P. Blackmoke. 



Salisbury, July, 1865. 



Notes on the Water Spider (Argyroneta aquatica). — It was wliile dredging for 

 fresh-water shells, last spring, that I had the pleasure of making the acquaintance of 

 this interestins creature. I had the net on the bank of the pond, and was examining 

 the result of the last draught, when a large spider ran out of the ooze and wiack at 

 the boltoin of the net. Being engaged wiih the shells, I gave little heed to the spider 

 uiitil I c.ime to put the rejectamenta back into the pond, which I make it a rule to do, 

 when I observed the spider to run along the surface of the water for some distance, 

 and then dive beneath it. This act (diving) showed me tliat it was no common spider, 

 but that the creature I had so carelessly tossed back into the water was the real Aranea 

 aquatica of Linneus, an aniinil for a sisihl of which many naturalists have longed. 

 By slipping the net beneath the spot where it had dived I fortunately succeeded in 

 recapturing it. It was a female, and had the usual reddish cephalothorax and legs, 

 the abdomen being blackish, with hairs having a hoary appearance when the head of 

 the creature is turned towards the observer. This one I lost owing to my having left 

 the jar in which she was kept uncovered. A second dredging in the same pond 

 resulted in the capture of more specimens, particularly a male and female: these two 

 I placed together in the same vessel, which was the cylindrical body of a glass shade, 

 live and a half inches high by four inches wide, to which a glass bottom was cemented 

 by Canada balsam. A sprig of Potainogeton crispus was placed in the jar to oxygenate 

 the water. The male almost immediately commenced to build a uest at the top of the 

 plant, jusi beneath the surface of the water: it was about an inch in diameter, nearly 

 globular, and of a transparent texture. From this air-filled lurking-place he would 

 often issue to attack boat-flies, caddis-worms or the larvae of dragon-Hies, which I had 

 put in to serve as food lor the couple. Meanwhile the female was busily engaged in 

 performing her nidifactory duties: her uest was built down at the bottom of the jar, 

 was less than that of the male, and of a different shape, being higher and not so broad. 

 Its chief peculiarity, however, was that the upper portion of it was made of white 

 opaque threads, or perhaps of the ordinary threads so closely compacted as to be im- 

 pervious to the lifiht, the lower portion of it being transparent, like that of the male: 

 this nest she filled with air, and, having frequent occasion to renew the supply, she 

 spun a ladder of threads to facilitate her frequent journeyings to and from the surface; 

 for the water spider, although of almost exclusively aquatic habits, is not a very dex- 

 terous swimmer, it being about as much as she can do to oveicome the buoyancy of 

 her air-clothed body. The air in the nest is constantly diminishing, owing to the 

 breathing of the spider replacing the oxygen by carbonic acid, which is quickly ab- 

 sorbed aiid carried off by the water: this renders frequent replenishment necessary, to 

 accomplish which the female creeps out at the bottom of the nest, and, after watching 

 an instant to see that all is clear, she walks up the ladder until her fore feet touch the 

 surlace of the water: she then turns as if on a pivot, and thrusts the apex of her abdomen 

 out of the water, with her two hind legs curved so as to bring the tarsi into contact with 

 the abdomen a little below the apex (that is, belotv when the si)ider is in the position 

 described), the one on the back and the other on the front of the abdominal region. 



VOL. XXIII. 2 z 



