Tlie Diamond-bacJc Moth. 
601 
The food plants of the diamond-back caterpillars are, by prefer- 
ence, turnip, cabbage, and other cruciferous plants, including not- 
ably what we know in England as " Charlock " {Sinapis arvensis,!^.), 
in Scotland as " Runches" or " Skellocks." It also attacks, amongst 
other weeds, " Jack-by-the-hedge " {Sisymbrium AUiaria, Scop.), 
a common hedge, or ditch-side plant of early foliage ; also the Hedge 
Mustard or Flixweed {Sisymbrium Sophia, L.) ; and it is stated to 
attack the Saltwort {Salsola Kali, L.), a plant to be found on sandy 
shores, but on inquiry I did not find that this plant had been 
observed as being infested in the past summer. 
The specific scientific name appended to that of Phitella (namely 
cruciferariim) is a very appropriate one, as it well describes the habits 
of the caterpillar in mainly feeding on cruciferous plants, namely 
those of the cabbage kind. The word Xylostella appended to 
Cerostoma, by which synonym this moth was formerly known, refers 
to the habit it was in early days of observation supposed to have of 
feeding on the Lonicera Xylosieum, L., the upright or two-flowered 
honeysuckle, a shrub to be found in thickets, aud more especially 
in Sussex.' 
Here, however, it seems to me that there may have been some 
confusion of species. As the case stands at the present day, the 
Cerostoma Xylostella of Stainton's Manual is distinguishable by 
several clear characteristics from Plutella crxcciferarum. 
The moth of C. Xylostella, besides being rather broadly yellowish- 
white along the hinder margin of the upper wings, " has an extremely 
narrow oblique white streak running half across the wing beyond 
the middle. " Also the caterpillars are green tvith a broad red stripe 
on the back and are tapering to the head end, and make a Jirm cocoon.^ 
During my own investigations, I found a very few green cater- 
pillars striped with brown or reddish brown which may possibly have 
been of this kind. 
The only parasite insect foe of tlie diamond-back caterpillars 
appears to be a small Ichneumon fly, Campoplex, given by John 
Curtis as jMiiiscus of Gravenhorst. This is only about a quarter of 
an inch in length, with ovipositor almost half the length of its body, 
and somewhat under half of an inch in expanse of the wings, black, 
with legs for the most part reddish, and with two pairs of transparent 
iridescent wings. This insect is stated by John Curtis " to be 
abundant in J uly upon almost every umbelliferous plant in fields 
and hedges, feeding in the flowers, and searching for caterpillars for 
the purpose of depositing eggs in them." 
Particulars of the Recent Attack. 
The following notes chiefly refer to first observations in the 
summer of 1891 of the diamond-back moth caterpillars, and the 
ravages on turnip leafage immediately following, and are for the 
most part given with date, also with name of sender and locality of 
' Manual of Brituh Botany, by Charles Cardale Babington, F.R.S. 
' See Stainton's Tineina, p. 70. 
VOL. U. T. S. — 7 R R 
