CRUSTACEANS 



Scientific literature appears to contain scarcely any specific records 

 relating to Crustacea in Worcestershire. Nevertheless, with a view to 

 the growing interest in questions of distribution and in the details of every 

 local fauna, it may not be superfluous briefly to indicate what groups of 

 Crustacea will beyond question be found represented within the limits of 

 the county, and some of the species the search for which will more or 

 less certainly be rewarded with success. 



The zoological class with which we are concerned is commonly 

 divided into two principal branches, the Malacostraca and the Entomos- 

 traca. The former of these two has attained a position by far the higher 

 in what may be called the scale of intellectual development, although by 

 parasitic habits a few of its members have fallen back into a state of 

 disgraceful degradation. Many persons are much surprised when first 

 they hear that the unfavoured woodlouse is not only a crustacean, but be- 

 longs to the aristocratic section of the class, and is distinguished even in 

 that section by having had the energy and enterprise to forsake an aquatic 

 existence for life upon land. The tremendous character of the change 

 from water-breathing to breathing air may be realized by any one who 

 attempts to reverse the process. The woodlouse is a terrestrial isopod. 

 An isopod is a sessile-eyed crustacean of the kind which as a rule has the 

 breathing apparatus in the appendages of the pleon or tail-part. Of the 

 land isopods some go wherever man goes ; some have their special pro- 

 vinces, districts, or isolated localities. England, without being very 

 richly provided, has several genera and species, and some of these are so 

 generally distributed over the country that their occurrence in this 

 county, as in others, may be affirmed with the utmost confidence. Such 

 are Oniscus asellus, Linn., ' very common throughout England, Scotland 

 and Ireland under decaying vegetable and animal matter, not only in 

 damp, but in the dryest localities ' ; ^ Porcellio scaber, Latreille, of which 

 Bate and Westwood say that they have ' found it partial to growing 

 vegetables, and it appears to possess a strong partiality for nearly ripe 

 wall-fruit,' this dainty animal ' being widely distributed throughout 

 England and Ireland';^ Armadillidium vulgare (Latreille), one of the 

 ' pill-millepedes,' not to be confounded with the larger and less common 

 G/omeris margwata, not a crustacean but a myriapod, with which it shares 

 the habit of rolling itself up into a complete ball. Bate and Westwood 

 expressly state that the Armadillidium is very abundant in the midland 



1 Bate and Westwood, British Sessile-eyed Crusttnen, vol. ii. p. 471. 2 /,(,,■ (-,7 p ^yj, 



126 



