DIAMOND-BACK MOTH. 121 
it on a field of Swedes to-day. As in 1894, my attention was drawn 
to this field by the constant presence of Gulls. In addition to the 
Herring Gull, Common Gull, and Kittiwake, I noticed a few Black- 
headed Gulls, an uncommon variety in this district, 
‘©The Turnip leaves are very much cut, but I have not been able 
to find many caterpillars. For the last two years we have not been 
affected by this pest, and the Turnip fields have been unoccupied by 
Gulls; so that everything tends to confirm my previous proposition, 
namely, that the Gull is in search of the caterpillar. 
‘‘T fear, however, that the remedy is rather drastic, for the Swede 
leaves in some places are badly cut, suggesting the nip of a bird’s beak 
rather than the ravages of a caterpillar. 
«¢P.S.—I have omitted to mention that although the Swedes and 
Yellow Turnips are both attacked, and the Gulls are feeding in- 
differently amongst both kinds of roots, it is only the Swedes that 
have apparently suffered from the birds’ bills. Have the Gulls greater 
difficulty in removing the caterpillar from the Swede leaf than from 
that of the common Turnip?’—(W. W.A.). 
The sample sent was of Diamond-back Moth caterpillar, then 
beginning to spin up, and in all probability, the attack being for the 
most part come to the stage of spinning for change to the chrysalis 
state, would be the reason why, although so much damage had been 
done, yet at the time so few caterpillars were observable on the leafage. 
The thin whitish webs of the chrysalis cocoons are not nearly so 
observable as the green caterpillars. In the sample sent me the web 
was completed by Sept. 17th, the day after receipt, and was so fine 
and open that I could easily see the characteristic markings on the 
pale head, and on the next segment, through it. 
On July 20th, Mr. Anderson favoured me with a further note that 
in the course of further examination he had come across a few more 
caterpillars, and that most of the Gulls had left the field, although a 
few still remained ; and that it appeared as if no further damage had 
been done to the crop (at least to any appreciable extent) since date of 
his previous letter. 
On July 20th, in course of examination of some Turnip leafage 
sent to me by Sir William Gordon, Bart., of Karlston House, Kirk- 
cudbright, N.B., relatively to a much distorted growth con- 
jecturally caused by injury from Cecidomyia (Gnat-midge) larve, I 
found a few specimens of caterpillars of Diamond-back Moth present, 
although the leafage sent had not been much eaten. The caterpillars 
were full, or nearly full grown, and still of a beautiful apple-green 
colour. 
On Aug. 21st the following observation was sent me, with speci- 
mens of Diamond-back caterpillars about fully grown and cocoons in 
