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The Diamond-hack Moth (Pkitella cruciferarum.) Zell. 

 By George Bolam, Berwick-on-Tweed. 



The year 1891 was remarkable, from an entomoloj^ical point of view, 

 from the pestiferous abandance of this small Moth, and in the agricultural 

 mind will long be associated with the ' Caterpillar Plague,' from which 

 the root crops suffered so serioasly. The insect which caused the damage 

 is the Plutella cruciferarum of Zeller,* the Gernstomo. xylostella of Curtis ;t 

 though not the C. xylostella of Stainton,;|: who applies that name to an 

 entirely different moth, and retains Zeller's designation of this species, as 

 also does Mr. South in his more recent " Synonymic List of British 

 Lepidoptera." 



The moth has been so often, and so accurately, described and figured, 

 that it is unnecessary to go over the same groand in a paper such as the 

 present, suffice it therefore to say that it is, roughly speaking, a small grey 

 inconspicuous looking insect, bearing a rather strong resemblance to one 

 of our common ' clothes moths.' The wings are narrow, the upper pair 

 thickly freckled with minute black spots, and having along their inner 

 margin (or, that is, along the hack when the wings are closed) a narrow 

 strip of paleochreous white, with three or four angular projections running 

 on to the darker colour, which have been thought to assume the appear- 

 ance of diamonds, and hence the popular name given to the moth, ft rises 

 from the grass or herbage, as we walk along, in a sudden, jerking manner 

 and usually makes only a short flight before alighting again ; if we follow 

 it to its resting place, we shall find a very narrow, greyish looking, moth 

 sitting crosswise upon a blade of grass, moving its white, many-jointed 

 antennae or 'horns,' about in front of it, and on being again disturbed, the 

 same tactics are pursued. 



The caterpillar, to the unassisted eye, is green, rather pointed towards 

 either end, and about half-an-inch in lensth when full grown, the magni- 

 fying glass disclosing many minute tubercles along its entire length, each 

 emitting a short black hair, while in some examples thei-e is more or less 

 indication of a darker stripe, along each side, jnst above the legs. They 

 are found most commonly upon the under side of the leaf, often sur- 

 rounded by a fine web, and, on being disturbed, drop from the food plant 

 and hang suspended by a fine silken thread, by means of which they can 

 afterwards regain their position. 



The insect is always very common in this country, and seems to be very 

 generally distributed, and it has besides a very wide geographical range, 



* Zeller, " Entomologische Zeitung," 1843, p. 283. 

 t " Farm Insects," by John Curtis, published in 1859. 

 :J: " Insecta Britannica," vol. iii., Tineina by H. T. Stainton, published 

 in 1854. 



