151 

 THE WOODLICE OF THE HULL DISTRICT. 



2nd Lieut. T. STAINFORTH. E.R.R.G.A. 



For some time previous to and duiing the early part of the 

 present war I made systematic collections of the terrestrial 

 isopods of the neighbourhood of Hull, and gave an account of 

 the results in a lecture to the Hull Scientific and Field Natura- 

 lists' Club. Since then a list of Yorkshire species by Mr. F. 

 Rhodes* has appeared, but as the present notes, confessedly 

 incomplete, are supplementary to his interesting paper, and 

 contain references noi only to new localities, but also to four 

 species and several varieties not included in Mr. Rhodes' list, 

 I offer no apology in publishing them. 



The British species of Woodlice are greater in num- 

 ber than is suspected by the casual observer, and I was 

 surprised to find that in the city of Hull itself I had taken 

 fourteen species, many of them in the very heart of the city. 

 Woodlice of one kind or another are ubiquitous, and this 

 seems somewhat remarkable since comparatively so few 

 forms of Crastacea have successfully exchanged an aquatic 

 for a terrestrial existence. To many species the presence of 

 free water is a nne qua non for their life's conditions, others 

 merely require damp situations, while a few species are tolerant 

 of dry conditions. Our largest species, the common Ligia 

 oceanica, in its mode of life at any rate, links the more typical 

 marine isopods with the terrestrial forms. It is one of the 

 most characteristic members of the littoral fauna of the Humber, 

 and in my own experience is never found away from salt or 

 brackish water. On the Humber shore it invariably lives near 

 high-water mark, in such positions that it must be submerged 

 at high water. During the present month (March), for example, 

 I have found it common on the shore at Sunk Island living 

 under chalk blocks upon which is a growth of Fitcus. In a 

 paper on ' Changes in the branchial lamellae of Ligia oceanica, 

 after prolonged immersion in fresh and salt water,' Miss 

 Dorothy A. Stewart f gives an account of some experiments 

 tending to prove that Ligia is able to withstand at least 24 

 hours of submergence in fresh water and for several (as many 

 as nine) days in salt water. She found that fresh water acted 

 much more rapidly than sea water in bringing about a fatal 

 result, and concludes that this seems ' to indicate that Ligia, 

 although it spends most time in terrestrial surroundings, 

 possesses a consideiable adaptability in regard to immersion 

 in sea-water, which is probably indispensable in an animal 



* ' The Terrestrial Isopoda (Woodlice) of Yorkshire.' The Naturalist, 

 1916. pp. 99-102, 121-123. 



t Mem. and Proc. Maiich. Lit. and Phil. Soc, Vol. 58, Part, i (i), 

 1913-14. 



1918 May 1. 



