199 



ABNORMALITY IN SPIDERS. 



WM. FALCONER, 

 Slaithwaite, Huddersfiehi. 



Mr. Parson's note (page 214), bears upon a subject, to which 

 arachnologists have hitherto given scant attention, and which 

 may therefore be considered not unworthy of more than passing 

 notice. It is now a matter of common knowledge that in both 

 the animal and vegetable worlds, types are not fixed, but admit 

 of a certain range of variability, which is of interest to, and 

 recognisable only by, systematists. Outside the permissible 

 limits, abnormality results. Amongst spiders cases of real 

 abnormality, the more pronounced deformities in, and defi- 

 ciencies of, structure, coloration and shape, are most exceptional, 

 and though in the course of a long experience as a student of 

 the arachnida, I have naturally met with several such examples 

 of one kind or another, they have nevertheless been exceedingly 

 few in number compared with the thousands of quite normal 

 form and aspect which have passed through my hands. 



The number, size, and arrangement of the eyes form very 

 important discriminatory characters in the diagnose of genera 

 and species of spiders, so that any peculiarity in them is readily 

 observed. Especially is this the case if some form of blindness 

 is present. This, when it occurs, may be either partial or total, 

 according to the number of eyes affected, and is usually asso- 

 ciated with a more or less abnormally shaped caput. One 

 would imagine that the more complete the degree of blindness, 

 the more severely would the unfortunate creature be penalised 

 in the struggle for existence and the less likely to escape a 

 violent death from the ferocious jaws and deadly beaks of its 

 numerous enemies. The range of vision in spiders, however, 

 is supposed not to be very great, and if they depend, as has been 

 surmised, upon other senses far surpassing our own in percepti- 

 bility, even more than upon that of sight, for preservation from 

 danger and for the capture of prey, then the deprivation will 

 be less serious in its consequences. How'ever this may be, 

 I can only remember to have seen during the last eleven years, 

 two individuals in which all trace of eyes had been completely 

 obliterated, the one described by Mr. Parsons in his note, and 

 the other, a female, Walckenaera acuminata BL, collected by 

 myself in Roundhay Park, Leeds, on November nth, 1908. 

 The latter had its copulatory organs fully developed, and the 



jgio May i. 



