DIAMOND-BACK MOTH. 107 



best tlianlis to all my contributors for the prompt care and courtesy 

 with which they were good enough to reply to my requests for 

 information. 



LiFE-HISTOKY AND HaBITS OF THE DiAMOND-BACK MoTH, 



Pliitella cniciferarum (of Zeller). 



This moth is common and abundant in this country in many places 

 during the summer, but it is rarely that bad attacks of its caterpillars 

 to the Turnip crops have been recorded. One of the first records of 

 really serious ravage appears to be that given by John Curtis, as 

 occurring near Petersfield, Hants, in August, 1837.* The next notice 

 of widespread presence and severe damage does not appear to have 

 taken place until 1851, when it was recorded on the high authority 

 respectively of Prof. J. 0. Westwood, and of Mr. Stainton ; and since 

 then, until the past summer of 1891, I am not aware of any large area 

 being infested in this country by this Turnip-leaf pest. 



Local attacks, of which observations were sent me, occurred in 

 1883 and 1884 ; f these were for the most part at widely separated 

 localities, — as near Harwich, Essex ; King's Lynn, Norfolk ; Liverurie, 

 Aberdeenshire, and (in both years) at a few places in Yorkshire ; and 

 it was from the benefit that appeared to be derived from the use of the 

 sciifflers, and quite certainly from application of nitrate of soda in 

 some of these cases of infestation, that I felt justified in suggesting 

 these measures on the outbreak of the threatened caterpillar devas- 

 tation of the past season. J 



Diamond-back Moth. — The size of these moths is only about, or 

 rather under, two-thirds of an inch in the spread of the wings, and to 

 ordinary observation when at rest they appear as brownish-grey moths, 

 about the size of furniture moths, but long and narrow in shape. 

 When at rest, and the upper wings laid along the back, with the edges 

 meeting, the pale patterns along these edges form diamond-shaped 

 marks, whence the English name "Diamond-back Moth"; if seen 

 sideways, the curved-up extremity of the wings, as shown at 3 and 4 

 in the figure on page 105, is very striking. 



On minute examination it will be found that the front wings are 

 long and narrow ; greyish brown, darker towards the centre, but 

 marked with some small brown spots in front ; a rather broad whitish 

 or ochreous-grey band runs along the hinder margin, with three 



* ' Journal of Eoyal Agricultural Society,' vol. iii. (first series), p. 71. 



•f See my ' Keport on Injurious Insects ' for 1883, p. 72 ; and for 1884, p. 81. 



X I have not enumerated occasions ■where this attack has been mentioned, as 

 matter of reminiscence, as having occurred ; for it is no easy matter to discriminate 

 from memory alone between attacks of various kinds of green caterpillars which 

 work by gnawing Turnip leaves. . . 



