n8 AMERICAN SPIDERS 



funnel in a crevice, under rocks, or in thick vegetable growth, and 

 then continue the silk out over the ground as an expansive sheet. 

 The spider hides in the funnel, and waits for insects to fall upon the 

 funnel or become entangled in the sheet webbing, whereupon it 

 rushes out and captures its prey. This type of web is called a sheet 

 web; it is the same in general plan as those spun by the American 

 grass spiders, by some wolf spiders, and by one group of atypical 

 tarantulas. The spiders that use this device for capturing insects 

 are usually agile creatures, which can rush to the location of their 

 prey with great speed. Their movement on the flat sheet has, in a 

 nice comparison, been likened to a skier gliding over the top of the 

 snow, whereas the bulky insects make headway on the yielding silk 

 like a man walking through heavy drifts. 



The sheet-web tarantulas are specialized creatures. They have 

 developed the best eyesight of all the mygalomorph spiders. Their 

 bodies are quite long and flat, and the tarsi of their long legs are 

 provided with an unpaired claw, as in the trap-door spiders. Since 

 much of their prey drops on the webs during the day, they hunt 

 equally well then as at night. Their spinnerets are frequently 

 greatly elongated and widely separated. The terminal segments of 

 their long lateral spinnerets are provided with many small spools, 

 from which can be spun a wide sheet of silk when the organs are 

 moved from side to side. Except for two genera (Hexathele of 

 New Zealand and Scotinoecus of Chile, which have six) only four 

 spinnerets are present. 



Most of the diplurids live in the tropics, where large species and 

 great sheet webs are conspicuous objects. In the United States 

 occur only two genera, and they are not notable for size or for 

 their web building. Microhexura is of particular interest because 

 it is one of the smallest of all tarantulas, averaging about one-eighth 

 inch in length. These tiny creatures carry their egg sacs around 

 with them in their jaws, held beneath the body between the front 

 legs much as in the fisher spiders. Three different species are now 

 known, one from the high mountains of North Carolina and Ten- 

 nessee and the other two recently discovered in the mountains of 

 Washington and Idaho. Although we can probably assume that 

 these tiny diplurids spin a sheet web, its exact character has not 

 been observed. They live under pieces of bark, decaying wood, 

 logs, and deep debris, in moist deciduous woods or fairly dense 

 coniferous forests. 



The species of Evagrus are considerably larger than Microhex- 



