302 THE SCOTTISH NATURALIST 



broods varying from thirty to fifty. Pierce ^ mentions that in 

 Porcellio IcBvis, Latr., the broods numbered from eight to 

 thirty, and in Arniadillidiujii vulgare, from twenty-nine to 

 seventy-nine, whilst a pair of Porcellionidcs prninosus (Brandt) 

 produced four broods of young in sixty-two days, there being 

 seventeen, sixteen, and twenty-one days between the broods, 

 which were small. In Armadillidmin the period of incuba- 

 tion is between fifty and ninety days. In Porcellio and 

 Oniscus development is more rapid. 



Moulting. — On leaving the brood-pouch the young are 

 pure white and have six pairs of legs. Pierce ^ records that 

 in Armadillidijim vulgare moulting takes place within 

 twenty-four hours of birth, and another between the 

 fourteenth and eighteenth days, after which the little isopod 

 has seven pairs of legs. They continue to grow, further 

 moults taking place on the twenty-eighth, thirty-sixth, 

 fifty-eighth, and sixty-eighth days. After the first moult, 

 future moultings depend very largely upon the food supply. 

 By the twenty-first day the young were under 3 mm. in 

 length, and at fifty-eight days they had not increased beyond 

 4 mm. Females not over 7 mm. long were found to be 

 capable of reproduction. The largest specimen found was 

 15 mm. in length and probably several years old. Casserley^ 

 has also described the process of moulting in this species, 

 and a very full account has been given by Aubin ^ of the 

 process in Porcellio Icevis, Latr., and P. dilatatus, Brandt. 



Food. — I have elsewhere'^ dealt with the economic 

 importance of these isopods, showing the serious injury they 

 occasion to various plants. They will feed upon almost any 

 vegetable matter, including fungi, algje, mosses, etc. An 

 interesting point in connection with their feeding habits is 

 the large amount of food they will consume when such is 

 plentiful, and the extremely small amount that is sufficient 

 to keep them alive for long periods. 



1 Pierce, U.S. Dept. Agric, Bur. of Entom., Bull. No. 64, pt. ii., 

 1907, pp. 15-22, pi. ii. 2 y^/^_ 



3 Casserley, Science Gossip, 1900, vol. vi. (N.S.), pp. 295, 296. 

 * Aubin, Jour?j. Econ. Biol., 1914, vol. ix., pp. 15-20, 2 figs. 

 " CoUinge, /9«r;/. Bd. Agric, 1914, vol. xxi., pp. 206-212, pi. 



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