178 Proceedings of the Royal Irish Academy. 



PORCELLIO. 



The genus Porcellio contains very nearly a quarter of all known species 

 of Woodliee, and ranges all over the world, though the great majority of 

 species are found in Europe and northern Africa. Only four species have up 

 to the present been taken in Ireland, as compared with six in Great Britain. 

 The two species {rathhei and ratzehurgii) which have not yet occurred in 

 Ireland are, however, included in the following table, as they are very likely 

 to be eventually taken here : — 



Species.^ 



A. Five pairs of tracheae.' 



(rt.) The basal joint of the flagellum about 



half the length of the terminal joint . ratzeburgii. 



[h). The two joints of the flagellum nearly 



equal in length .... rathkei. 



B. Two pairs of tracheae. 



I. Lateral plates of the first body-segments pro- 

 duced backwards, more or less sharp, 

 (a) Apex of telson rounded .... dilatatus. 

 (b). Apex of telson sharp-pointed. 



{¥). Basal joint of flagellum much 



longer than the terminal joint jdctus. 

 (b^). The two joints of the flagellum 



nearly equal in length . . scaber 

 II. Lateral plates of the first body - segments 

 hardly produced backwards, blunt 

 and rounded 

 Porcellio scaber Latreille. 



THs is one of our very eommonest 

 species. It is often found in company 

 ■with Oniseus asellm, and, like that 

 species, may he found in. large colonies 

 under the bark of trees. It also exists 

 in enormous numbers amongst decaying 

 seaweed and debris on the seashore. 

 Though usually of a uniform gi'ey, 

 specimens with reddish side-plates are 

 often seen, and bright-coloured and 

 speckled specimens are not unusual. 

 Equally common in Great Britain, 



' These diaracteristics are those given by M. Budde-Iaind in bis " IsopodaTeiiesma." 

 - This characteristic, wliich is easily detected in living specimens, is hardly to he recognized in 

 preserved ones. 



• 



• 





■ 



laevis. 



Porcellio 



scaher, i 



in fact, 



seems to range 







35 



34 



iO 



39 









33 



36 



37 38 





27 



28 



29 



32 









26 



2S 



30 



31 





16 



17 



2i 



23 



22 







13 



18 



19 



21 





9 



10 



ii 



13 



20 



2 



8 



7 



11 



12 





1 



3 



5 



6 







over the 



whole 



world 



wherever the 



climate is sufficiently temperate. 



