42. The Evolution and Distribution of Indian Spiders 



belonging to the Subfamily Aviculariinae. 



i 



By F. H. Gravely, M.Sa, Assistant Superintendent in the 



Museum 



[With Plate XXXI]. 



On pp. 201-210 of the last volume of this Journal, atten- 

 tion was called to the correlation of distribution with pro- 

 gressive specialization in Passalid beetles of the subfamily 

 Aceraiinae, in whip-scorpions and in crinoids. I have now 

 obtained evidence showing that a similar correlation exists in 

 the case of certain spiders. The evidence is, unfortunately, 

 less complete, as the material available for reference in 

 Calcutta is almost entirely Indiau, Assamese and Burmese. 

 But it is so strong as far as it goes that a record of it seems 

 desirable. Specialists dealing with material from other parts 

 of the Indo-Australian area will no doubt be able to com- 

 plete it later. 



The Aviculariinae are a subfamily of Mygalomorph spiders, 

 and include the largest of these spiders found in India, where 

 they are popularly called Tarantulas. 



The special interest of Mygalomorph spiders from a 

 zoogeographical point of view has already been emphasized 

 by Pocock (1903, pp. 341-2). He points out that "owing to 

 the relatively large size and great weight of the newly hatched 

 young of the Mygalomorphae, coupled with the reduction in 

 the number of spinning appendages and the greater simplicity 

 of the silk-glands, it seems probable that aerial sailing is not 

 practised to any great extent by the members of this sub- 

 order." In a footnote he adds, "The young of the only 

 British representative of this group, namely Atypus, have 

 been seen to scatter over small areas by this method of travel- 

 ling (F. Enoch, Tr. Ent. Soc. 1885)" and notes that the distri- 

 bution of this genus is exceptionally wide. 



Of the eleven groups into which Simon divides the Avi- 

 culariinae (1897, pp. 918-9) five are characterized by the 

 presence of stridulating organs between the chelicerae and 

 palps. All but one of these five are exclusively Indo-Australian, 

 the exception being the Harpactireae from Africa. In the six 

 remaining groups stridulating organs of this nature are found 

 only in the genus Psalmopeous (group Avicularieae). 1 * 7: * l% * u ~ 



With 



1 Published with the permission of the Trustees 

 seum. 



