Pack Bee KSFORD AND Foster — The Woodlicc of IrelamL 169 



Table II. — List of Species of Woodlice with number of County Divisions 



FROM WHICH EACH HAS BEEN EECOEDED. 





County 

 Divisions 





Countj' 

 Divisions 



Ligia oceanica, 



24 



PorcelUo scaber, 



40 



Trichoniscus pusillus, . . 



40 



,, pictus, 



20 



„ vividus, . . 



4 



,, dilatatus, 



14 



,, roseus, . . 



17 



, , laevis, 



S 



,, pygmaeus, 



14 



Metoponorthus pruinosiis, 



10 



„ stebbingi, 



1 



„ cingendus, 



10 



Trichoniscoides albidus, 



4 



„ melanurus, 



1 



Haplophthalmus mengii, 



8 



Cylisticiis convexus, . . 



11 



„ danicus, 



2 



Annadillidium vulgare, 



23 



Philoscia muscormn, . . 



40 



,, pulchellum, 



6 



,, couchii, 



1 



„ nasatum, 



3 



Platyarthrus hofimannseggii, 



S 



Eluma purpurascens, 



1 



Oniscus asellus, 



40 







In order to facilitate the identification of any species, we give (Plate YIII, 

 fig. 1) a diagrammatic view of the dorsal surface of a Woodlouse, and also (fig. 2) 

 a face view. 



The " tracheae " on which some of the distinguishing characteristics are 

 based, and which are not shown in the diagram, are seen as white spots in the 

 breathing-plates or pleopods, which are borne under the abdominal segments. 



It may be well to note here that the colouration of some of the species 

 presents many variations, rendering this character of little value in classi- 

 fication. Fiu'thermore, in the examination of specimens preserved in spirit it 

 is found that ia many cases the life-colours are entirely changed, as in 

 Trichoni'icus roseus, which, on immersion in spirit, almost immediately loses its 

 bright rosy colour and becomes •^\n.te,OT: Metoponorthus pruinosus, from which 

 the bluish bloom is instantly removed. 



Coming now to a more detailed re%iew, we may remark that the twenty- 

 five species 1-mown to inhabit Ireland are included in twelve genera. The 

 characteristics which distinguish these genera may be set out in. tabular form 

 as follows : — 



Genera.' 



A. The two rami of the uropods alike in shape. 

 I. The flagellum with more tlian ten joints. 



(a). Abdomen broad ..... Ligia. 

 (h). Abdomen narrow Zigidium. 



' By the aid of this table, which is adapted from that published by Wehh and Sillem in " The 

 British Woodlice," 1906, it is possible to identify the genus to which any given specimen belongs. 

 For the benefit, however, of auyone who is not acquainted with these tables, it may be well to take a 



