A HISTORY OF HERTFORDSHIRE 



known for the whole of Great Britain and Ireland, only reaches the 

 number of twenty. Of these one is found in Ireland and has not 

 hitherto been found in England, while five have been found in England 

 which have not yet been discovered in Ireland. Two of the twenty 

 species are not to be expected at any great distance from the coast, and 

 a third is perhaps only a recent importation into our island, an immi- 

 grant from the continent. Of the ten species found in the Berkhamsted 

 garden one was an addition not merely to the fauna of the county but 

 to the fauna of the country, completing the score of which the United 

 Kingdom can boast. 



The Oniscoidea, or terrestrial isopods, best known among us by the 

 name of woodlice, and in French as cloportides or door-nails, are divided 

 into four principal families the Ligiida?, Trichoniscidae, Oniscidae, and 

 Armadillidiidas. These are separated by numerous differences, and united 

 by numerous points of agreement. All in common have sessile eyes, 

 unless they happen to be blind. All in common have seven pairs of 

 trunk-legs, though as a rule they quit the egg with the seventh pair un- 

 developed or ineffective. All in common have the breathing apparatus 

 not connected with the head or trunk, but pertaining to the appendages 

 of the pleon or tail part, the branchial structure being sometimes modi- 

 fied the better to suit atmospheric respiration. In all these respects they 

 differ strikingly from the crayfish, though equally with it belonging to 

 the Malacostraca. With the first of the four families, the maritime or 

 coast-loving Ligiida?, we are not here concerned. The other three fami- 

 lies are represented in Hertfordshire by nine genera, including the ten 

 species already referred to, on which some brief notes may be offered. 

 The first three species to be mentioned belong to the family Trichonis- 

 cidas. 



Trichoniscus roseus (Koch) has been described under two other 

 generic names, Itea and Pbilougria, the latter meaning a lover of damp, 

 which would be a fairly appropriate designation for almost all the iso- 

 pods that ever existed. The specific name roseus refers to a character 

 which the inexperienced would little expect to find, and which is in fact 

 very rare, in a woodlouse, namely the beautifully delicate rose-tint of its 

 colouring. Many species display bright colours and highly effective 

 patterns, while some are modestly dressed in white or creamy hues, and 

 others in sober greys and browns. But no other species is at once so 

 beautiful and so unobtrusive as the little Tricboniscus roseus. Its distribution 

 is widely extended. It is very agile, like many others of its family. It 

 may not have a feeling for poetry, but by all its manoeuvres to escape 

 observation it shows plainly that, if ' many a rose is born to blush un- 

 seen,' such is the privacy it earnestly desires for itself. 



Tricboniscus pusillus, Brandt, is a still smaller species, which has 

 passed under the same series of generic names and also under three 

 specific names other than that which is proper to it, one of these syno- 

 nyms being ce/er, in allusion to the great celerity of its movements, by 

 which it is quite capable of foiling the efforts of a pursuer who is 



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