THE AERIAL WEB SPINNERS 183 



isolated groups only imperfectly bridged by intermediate forms, if 

 at all. 



The big- jawed spiders of the subfamily Tetragnathinae are in 

 certain respects among the most generalized of all orb weavers. 

 Most are greatly elongated spiders with very long, thin legs; the 

 chelicerae are of great size, especially those of the males, which 

 often project forward in a horizontal position. During mating, the 

 chelicerae of the female are gripped in those of the male by means 

 of long spurs that clamp the fangs, and, thus firmly hooked, are 

 rendered impotent. Most tetragnathids live in grassy areas, and are 

 especially common on the border of swamps and along streams. 

 Some place their snares horizontally over and close to the water, but 

 more frequently they are inclined or vertical, and framed in grass 

 or shrubs. The snare, which has an open hub, is quite delicate, and 

 is best suited to the capture of midges, mosquitoes, crane flies, and 

 other small insects with weak flight. 



The stilt spiders of the genus Tetragnatha, which appress their 

 slender bodies and legs closely against stems or hang as inanimate 

 straws in the center of their webs, are the best-known members of 

 this series. When disturbed, they drop on their draglines, often to 

 the surface of the water, over which they stride like aquatic bugs. 

 A dozen or more species occur in our fauna, most of them widely 

 distributed and abundant. One of the largest is the half-inch-long 

 Tetragnatba elongata, a grayish stick spider with great jaws longer 

 than its carapace. Even commoner is Tetragnatha laboriosa, a 

 smaller, yellowish species with a silvery abdomen, which lives in 

 grass, often in dry areas. 



The thick-jawed spiders of the genus Pachygnatha resemble the 

 stilt spiders, but their chelicerae are shorter and heavier, inclined 

 downward, and their legs are shorter. They live near the soil in 

 deep grass or under debris in damp places, cattail swamps being 

 especially favored. They do not spin a usable web, but wander in 

 search of small insect prey, as do the short-sighted vagrant spiders. 

 They are limited quite largely to the north temperate zone, and are 

 replaced southward by smaller, globose species that still use an orb 

 web as a means of capturing insects. These latter belong in the 

 genus Glenognatha, and differ in having the single tracheal spiracle 

 advanced far in front of the spinnerets. Our best-known species is 

 Glenognatha foxi, an eighth-inch-long, pink and silver spider of 

 quite globose shape, which lives in meadows and grassy situations 

 all over the South. Its delicate orb web, three or four inches across, 



