428 ON SOME RARE ARACHNIDS 



A. Sturmii on the other hand is a much greyer spider. 

 Few examples show any yellow at all. The oblique lines on 

 the fore part of the abdomen are nearly always conspicuous 

 and white, not yellowish. The hinder part of the abdomen 

 shows on each side a broken white dentated line. These 

 lines converge towards the spinners, and their margins are 

 bordered within by correspondingly indented greyish brown 

 bands. The hinder part of the portion of the abdomen in- 

 cluded by these lines is usually suffused with greyish brown. 

 A branched central marking may be present, but I have not 

 yet seen an example in which it was well developed. 



The 7}iales of triguttatus are usually yellowish brown as to 

 the abdomen, and of Sturmii greyish brown. In either case 

 the abdomen may be quite without any pattern, but frequently 

 triguttattis bears three large yellow macules at the anterior 

 part, and Sturmii a dentated pattern on the posterior part. 



The females are very easily distinguished by the vulvae, 

 which I here figure (see plate). Drawings are much more 

 useful than descriptions in this connection. 



The male palpi are figured by Chyzer and Kulczynski, and 

 Bosenberg. They draw their distinctions from a dentigerous 

 process placed on the inner side of the palpal organs. This 

 is a fairly good but variable distinction, and the difference 

 after all is only one of degree. There is, however, an excellent 

 difference in the palpal organs. This is best seen from the 

 inner side, but is also visible from above. It is difficult to 

 describe, so I give figures showing its position amongst the 

 processes of the palpal organs, and also others showing its 

 details of structure. I think it will be found useful, and when 

 once it is appreciated the males can be easily distinguished. 

 The whole palpal organs and tarsus are distinctly larger and 

 bulkier in A. Sturjfiii than in A. triguttatus. I believe that 

 Blackwall* possessed both species, which he included under 

 the name of Epeira agaletia (Bl.). I think his descriptions 

 of the abdomen refer to A. Sturmii, and those of the sexual 



* Spiders of Great Britain and Ireland, p. 334, pi. xxiv., fig. 242. 



