OF WASHINGTON. 105 



diidae (micro-theridiidae) there is little difference in size between 

 the sexes. In the Epeiridaeand Theridinse the male is commonly 

 smaller, often very much smaller ; in the Oxyopidae and Lycos- 

 idas there is not much difference in size, and with the Attidae the 

 males are never much smaller than the females. In the male sex 

 of Thomisidae, Epeiridae, some Theridiidae, and a few Clubionidae 

 the legs are proportionally or actually longer than in the female. 

 The difference in coloration between the sexes of many Attidae 

 has been dwelt upon by Prof. Peckham. It is far more promi 

 nent in this family than elsewhere in spiders. The Thomisidae 

 often show slight differences, and they are, in a few cases, I think, 

 due to sexual selection. In at least one species {Xysticus tri- 

 guttatus} there are two forms of the male, one colored as the 

 female, the other, and much more common form, marked in a 

 different manner. In the Oxyopidae, Oxyopes salticus shows a 

 very marked difference in the color of the sexes. In the Lycos- 

 idae there are few cases, none very prominent. The male of 

 Lycosa ocreata has the tibia I clothed with long, black, erect 

 hair, which might well be considered as an ornament. In sev 

 eral species of Pardosa the male is very much darker than the 

 female. In some Theri diidae certain parts are more brightly 

 colored in the male sex. In Latrodcctes\he male is much marked, 

 and resembles the young of both sexes. In a few species of 

 Dictyna the male is of a different color from the female. 



The secondary structural characters in spiders are perhaps 

 more interesting and less understood. I know of no case in 

 either the Thomisidse or the Lycosidag. In the Attidae we quite 

 frequently notice that the mandibles of the male are much longer 

 and larger than in the female, as Zygoballus, Philceus, Epiblc- 

 mum scenicum, and Icius mi trains. In the males of some 

 species of Habrocestum there are small projections on the tips of 

 the patellae and tibiae of the third pair of legs. These projections 

 are sometimes prominently colored, and are probably for orna 

 ment. In the Tetragnathidae the mandibles of the male are 

 usually larger and furnished with more teeth than in the female. 

 Yet in the female they are much elongated. It is probable that 

 this character is partly due to the general lengthening of all parts 

 of the body, and later was especially modified in the male. But 

 not all long and slender spiders have elongate mandibles ; as in 

 Hyctia and Tibellus they are of usual size. 



In the Epeiridae we notice that in the males of some species 

 the tibiae of the second pair of legs are thickened, and thickly 

 clothed with stout spines, while the metatarsi are curved ; for 

 example in E. trivittata, E.foliata, etc. Sometimes the tibia 

 bears a curved projection as in Maliadeva. These characters 

 may be of so Tie use in holding the female and preventing her 

 from turning and biting the male. In the males of a few species 



