AQUATIC INSECTS OF FRESHWATER 



ing patterns and shades in brown. It may be seen on the wing in early 

 summer, deposits its eggs, encased in a gelatinous capsule, on the under 

 side of floating leaves near the edges. The larvae burrow into the leaf 

 until too large to find a refuge, when they bite off oval pieces and fasten 

 them to other parts of the leaf with a gelatinous secretion or silk; and in 

 this secure retreat the molts take place. The more general species are 

 H. obliterans, Fig. 232, which lives on water plants in greenhouses, rarely 

 out-of-doors, H. albalis, H. allionealis, A. ekthlipsis, H. icciusalis, H. 

 obscuralis, H. stenialis, and six other species on the Atlantic slope of 

 the United States. 



China-Marks or Cataclysta are small moths, rarely over ^ inch 

 spread of wings, of which those of the male are white, with bkck mark- 

 ings and of the female brownish with darker markings. The larva is 

 brownish and is most often found among the duckweed, of which it spins 

 together the leaves to form a casing. The more general species are C. 

 fulicalis. Fig. 232, and C. bifascialis, with three other species not so 

 generally distributed in the United States. 



There are several other genera of Lepidoptera which are semi-aquatic 

 but which are not generally distributed and need not be mentioned here. 



Order Arichnid^. This order, consisting of the spiders, scorpions 

 mites and harvest-men, possesses certain characteristics in common with 

 the Crustaceans with which it is allied. All the families have a com- 

 bined head and thorax, a globular, ovate, cylindrical 

 or triangular abdomen connected by a slender waist; 

 eight legs attached to the thorax, and simple eyes, 

 varying from 2 to 12 in number, placed in two trans- 

 verse rows. The mouth parts are armed with 

 powerful forceps to seize, hold and poison their 

 prey, below which is a pair of maxillae, somewhat 

 resembling a pair of legs. The spinning organs 

 are situated at the tip of the abdomen and the ^■„:;^,:r^^^^ 

 breathing apparatus is at the forward portion of the surrounded with air. Enlarged. 

 abdomen. It serves the purpose of lungs, the colorless blood circulates 

 around and through it and is aerated by the absorption of air. There is 

 no metamorphosis, as the young,just issued from the egg, exactly resembles 

 the adult. Molting continues after the spiders have reached the adult 

 stage. All the aquatic genera belong to the Senoculina, or six-eyed group. 

 One species, Argyroneta aquatica. Fig. 233, about ^ inch long, spins a 

 baglike web of silk half the size of an acorn among the water plants with 

 the opening below the surface, and lives in it under the water, taking a 

 bubble of air into it each time it comes to the surface; efi^ected by erecting 



273 



