ß26 Theophilus S. Painter, 



with regard to the presence of a pair of small chromosomes in the 

 gray males, and the absence of this bodies in these tufted males. On 

 this cytological basis. an attempt was made to explain the dimorphism. 

 If intermediate forms exist. however, as stated by Emerton, 

 "Common Spiders", p. 60, then the explanation would have to be 

 modified. 



The present study was made in order to determine the exact nature 

 of the dimorphism and the particulars in which the so called "Inter- 

 mediate forms" differ from the typical males of botli types. Two 

 other points were investigated. First, the ratio of the females to 

 males, in nature, and the ratio of the gray to tufted males. Second, 

 observations have been made on the dancing of the two types, it 

 being stated by the Peckhams (1889a) that the two varieties of 

 males behave difi'erently in this regard. 



As far as I can determine, Maevia vittata was first discribed by 

 Hentz, in 1845, under the name of Ättus vittatus, the gray male, 

 and Athis 7iiger, the tufted male. He assigns them, thus, to diiferent 

 species. C. Koch, in his work entitled, "Die Arachniden", describes 

 the gray male as Plexippus undaüis, and the tufted male as Maevia 

 penicillata. He assigns the two species to different genera. 



The Peckhams (1889b), were the first to assign the two forms 

 to the same species, Astia vittata. They remark that we have here 

 males, "presenting two distinct varieties; the first has the thoracic 

 part of the cephalothorax light brown, . . .; the second variety 

 {niger), has the cephalothorax black, . . ." etc. Farther on, "Inter- 

 mediate between these two varieties, is one which is nearly as dark 

 as niger with pale legs but wäthout cephalic tufts. ... As this is 

 an extremely common species, we have compared large numbers of 

 them but have never found the tufts present in the first variety, 

 which most resembles the female." "Attidae of North America", 

 p. 70. 



The dimorphic males have been described by many other authors, 

 Emertün (1891), Simon (1903), etc. 



My material has all been collected in a plot of woods near 

 New Haven, by the usual method of sweeping the grass and low 

 bushes with a net. An area, of perhaps two acres, was swept 

 repeatedly, in this way, during the late afternoon. This is the 

 best time for collecting, as far as the experience of the Author 

 goes. Altogether, 156 specimens have been obtained, of which 



