WOODLICE 9 



Thompson, 1952). The degree of nocturnal activity in different 

 species is correlated with the ability to withstand water-loss by 

 transpiration (Cloudsley-Thompson, 1956). 



Isopods show a regression in the size of their sense organs 

 which may be correlated with reduction in the rapidity of move- 

 ment on becoming terrestrial, for the aquatic forms are rapid 

 swimmers. Lz]^'/^ spp. however, which can run particularly rapidly, 

 have retained the big eyes of their marine ancestors. 



In a recent review of the adaptations of woodlice to the terres- 

 trial habitat, Edney (1954) concludes that different species can 

 withstand terrestrial conditions of drought to varying degrees, but 

 probably all species spend most of the time in an atmosphere 

 saturated with water vapour and merely differ in the length of 

 time that they are capable of surviving away from dampness. 

 Thus even Annadillidium and Hemilepistus spp. can venture into 

 dry places with immunity only for comparatively short periods. 

 Edney also suggests that the reason why so little progress has been 

 made toward full exploitation of the land by woodlice may lie in 

 the fact that the conquest of the land by the Isopoda took place 

 via the littoral zone, for Ligia and Halophiloscia are undoubtedly 

 primitive morphologically. Now animals crossing this zone may 

 well be subjected to extremely high temperatures, and the ability 

 to lose heat by evaporation of water may have considerable sur- 

 vival value in all species. 



Food and feeding habits 



Woodlice are omnivorous and no doubt useful as scavengers. 

 Some species are of economic importance because they do not 

 confine their attention to dead and decaying matter but some- 

 times attack seedlings, ripe fruit such as plums, peaches or melons, 

 and mushrooms — indeed they will eat anything that is soft and 

 juicy though they do more mischief by disfiguring than by con- 

 suming any large quantities. They are sometimes difficult to dis- 

 lodge from hot houses as they find shelter in every little crevice. 



NichoUs (1931) has shown that although Ligia oceanica feeds 

 principally on Fucus vesiciilosus and other algae, nothing edible 

 comes amiss, particularly if it be in the nature of animal offal, and 

 cannibalism frequently takes place in captivity. The gut contents 



