THE THERIDID^ 



123 



middle (fig. 287). The front of the head is rounded and a 

 third as wide as the thorax. The eyes are close together and 

 all about the same size. The males have the cephalothorax 

 larger and rougher, but in size and color resemble the females. 



Latrodectus mactans. — 

 This is the largest spider 

 of the family. It is some- 

 times half an inch long, 

 with the abdomen round 

 and the whole body black, 

 except a bright red spot 

 underneath and one or 

 more red spots over the 

 spinnerets and along the 

 middle of the back (figs. 

 289, 290). The spots turn 

 yellow or white in alcohol. 

 The cephalothorax is 

 about as wide as long, and 

 the grooves between the 

 head and thorax are deep. 

 The lateral eyes are 

 farther apart than usual in 

 this family. The legs of 

 the male are much larger 

 than those of the female, 



and each joint is orange brown in the middle and black at the 

 ends. The abdomen of the male has a row of red and white spots 

 in the middle line, as some females do, and across the front end, 

 and along the sides four pairs of stripes, red in the middle 

 and white at the edges (fig. 291). The young of both sexes 

 are colored somewhat like the male and, when very small, have 

 very little black on them. The males vary much in size, some 



Figs. 292, 293, 294, 295. Argyrodes trigonum. — 

 292, side of female enlarged eight times, the 

 dotted line showing the abdomen bent dovvn- 

 ^vard. 293, tip of abdomen seen from above. 

 294, top of cephalothorax. 295, cephalothorax 

 of male. 



