CRUSTACEANS 



unready and inexpert. Its glossiness, its nimble movements, its red- 

 brown colour, and its angular outstanding spiny little second antennae 

 make it easy of recognition. 



Haplophthalmus danicus, Budde-Lund, was not known in England 

 until discovered by Dr. Norman, who says, ' I have found this pretty 

 little species in my garden here (the Red House, Berkhamsted, Herts). 

 It occurs in company with Trichoniscus roseus in a cool greenhouse. The 

 genus is allied to T'richoniscus. The species may be recognized by its 

 simple eyes and the longitudinal series of tubercles which pass down the 

 body. Other specimens in my collection are from Denmark (Copenhagen 

 Mus.). It has also been found in Norway, Holland, and France. A 

 near ally, H. mengii, Zaddach, which is known to have a wider distri- 

 bution, may be found in Great Britain. It is distinguished from its ally 

 by having six longitudinal finely crenulated ribs passing down the body, 

 instead of the rows of tubercles, and by the peculiarity of having two 

 very prominent ribs on the back of the third segment of the pleon.' 1 



This quotation may serve to stimulate research for these minute 

 forms, in which, as the generic name implies, the eyes are simple. In 

 Trichoniscus the eyes have each three visual elements. Haplophthalmus 

 danicus is greyish white in colour, and not quite a sixth of an inch long. 

 The companion species is scarce an eighth of an inch long, but Professor 

 Sars says that 'it moves very slowly, and, in spite of its small size, is 

 easily detected by the pure white colour of the body.' Yet, as the 

 young ones of some of the larger woodlice are also slow-moving, small 

 and white, there is opportunity for untrained eyes to be deceived. 



The six following species are all included in the family Oniscidae : 



Oniscus aseHus, Linn., is found not only here, but everywhere, if by 

 everywhere we are contented to understand Europe and North America, 

 with the Azores, Iceland, and Greenland. As it attains a length of two- 

 thirds of an inch, and is one of the broadest of our woodlice, its familiar 

 form can be discerned by most persons without the aid of microscope 

 or even spectacles. 



Philoscia muscorum (Scopoli), though not nearly so large as the 

 preceding, is of respectable size and very common, the inseparable com- 

 panion of rural life. 



Platyarthrus hoffmannseggii, Brandt, is humble in size, though so 

 ample in name. Its legs are short and thick, and the second antennae 

 have the joints of the peduncle flattened, whence Brandt gave it a generic 

 name meaning broad of limb. But it has no eyes, so that another 

 author, Schobl, later on, in ignorance of Brandt, named the genus Typhlo- 

 niscus, meaning the blind woodlouse ; while in between these two authors 

 Koch called the species Itea crassicornis, in allusion to the thickness of 

 its antennae. Notwithstanding its extensive distribution, the only chance 

 of finding it is by peeping into ants' nests, and then when the disturbed 

 ants are scurrying about, as if the world depended on the security of 

 their offspring, it is an almost pathetic sight to see the little white, sight- 



1 Annals and Magazine of Natural History, ser. 7, vol. iii. p. 73 (1899). 



185 



