1917- Carpenter. — Useful Shidies for Field Naturalists. 69 



want of observation in former years, but to an actual change 

 in the mode of Ufe of the species observed. Thus the study 

 of an obscure group of insects is found to have an unexpected 

 economic bearing, and the behaviour of the creatures in 

 relation to cultivated plants may give the naturalist an 

 opportunity of noticing change of habit on a large scale 

 — a fascinating line of enquiry from the biological point 

 of view. 



In the case of one springtail, at any rate, such a change 

 of habit has been certainly observed. Tobacco is a newly 

 introduced crop in Ireland, raised entirely from seed, so 

 that no insect-pests can have been introduced with it. In 

 April, 1907, tobacco seedlings from Kilkenny were found 

 to be covered with multitudes of dark greyish springtails, 

 which proved on examination to belong to Isotoma tenella, 

 a Finnish and North German species hitherto unrecognised 

 in the British Islands.^ There can be no doubt that this 

 scarce insect had suddenly increased in numbers through 

 the introduction of a new crop which happened to afford a 

 large and suitable food-supply. 



It is interesting to notice also that the tobacco grown in 

 Ireland has attracted several of our common and always 

 abundant farm-pests such as wireworms (Agriotes larvae), 

 and caterpillars of the Cabbage Moth [Mamestra hrassicae) 

 and of its ally il/. oleracea, as well as the familiar " surface 

 caterpillars " of the Turnip Moth {Agrotis segetum). 



Many years ago I received from a Westmeath farm a 

 number of root-eating beetle-larvae which none of my 

 friends, specialists in the Coleoptera, were able to identify. 

 In February, 1908, the same larvae turned up again — 

 injurious to roots of oats and grasses in Co. Dublin. On 

 this occasion I succeeded in rearing a beetle which proved 

 to be the common Dascillus cervinus f then I learned that 

 similar observations on the habits of the larva had been 

 made in Denmark by Prof. J. E. V. Boas,^ and that some 

 description of its structure had been given by Dr. C. J. 



^See Irish Naturalist, vol. xvii., 1908 (pp. 174-6) and Econ. Proc. R. 

 Dublin Soc, voi. i. (1908, pp. 574-6). 



^Econ. Proc, R. Dublin Soc, vol. i. (1909, pp. 589-592). 

 ^Tidsskift for Landbrugets Planteavl, vols. iii. x., 1896-1903. 



