14 



THE STUDY OF INSECTS 



Uloborus. — The spiders of this genus make round webs which re- 

 semble at first sight those of the orb weavers; but they differ from the 

 ordinary orb webs in that the spiral thread is made of the hackled-band 

 silk. These webs are nearly horizontal, and are usually made between 

 stones or in low bushes. The spiders of this genus are not common, but 

 they are widely distributed. 



Family Theridiidve 



The Comb-footed Weavers 



Many are the kinds of webs spun by different spiders. Some of them, 

 as the orb webs and the funnel-webs, delight us with their wonderful 

 regularity of form; while others appear to be a mere shapeless maze of 

 threads. Such are the structures whose presence in the corners of our 

 rooms torment thrifty housewives, and which arc disrespectfully termed 

 cobwebs. The most common spinner of cobwebs is the abundant house- 

 spider, Theridion tepidariorum, which spins its irregular webs composed 

 of threads extending in all directions with no apparent regularity, in any 

 convenient corner. The spider, which hangs in its web with its back 

 downwards, will serve well as a representative of this family. 



These spiders have eight eyes and 

 three tarsal claws. In addition, they 

 have on the tarsus of the fourth pair 

 of legs a distinct comb consisting of a 

 row of strong, curved, and toothed 

 setae (Fig. 29). As the presence of this 

 tarsal comb distinguishes these spiders 

 from all others, they may well be called 

 the comb-footed spiders. The comb is 

 used for flinging silk, often in a quite 

 liquid state, over the entangled prey. 

 Although the house-spiders are the most famil- 

 iar members of this family, a large number of 

 species spin their webs in the fields on bushes. 

 These webs usually consist of a flat or curved 

 sheet, under which the spider hangs back 

 downward. This sheet is supported by threads 

 running in all directions to the neighboring ob- 

 jects. Frequently there is a large number of 

 these supporting threads above the web, which 

 serve the additional purpose of impeding the 

 flight of insects, and causing them to fall into 

 the web, where they are caught. A few species 

 which do not live in webs and spin very little, 

 are found under stones, or in the moss and 

 leaves, and run with great rapidity. 



One spider of this family, Latrodcctits mac- 

 lans, commonly known as the "black widow" 

 or hour-glass spider is, outside of the tarantulas, the one poisonous spider 

 in this country. It is a coal-black spider with a red marking in the form of 

 an hour-glass on the underside of the abdomen (Fig. 30). The female is 



Fir,. 2Q. — Comb of Theridion; b, a tooth 

 of comb, enlarged. (From the Spider Book, 

 Doubleday, Page and Company.) 



Fig. ?o. — The hour glass spider. 

 Ventral side aboye to show the red 



marking 



