28. THE ENTOMOLOGIST. 



LEPIDOPTEROUS LARV^ IN WALNUTS. 



By F. V. Theobald, M.A., F.E.S. 



Economic Entomologist to the S.E. Agricultural College. 



Seeing Mr. Adkin's paper on Carpocapsa pomonella [ante, p. 2) 

 as a nut-feeder (which is of interest economically), I thought 

 that perhaps a few additional notes on larvae in walnuts might 

 not be out of place. For some years past I have been investi- 

 gating the insect-pests of the walnut, and have found the larvae 

 of two moths present in the nuts, namely, Carpocapsa splendana 

 and Plodia interpunctella. So far I have never come across 

 C. pomonella myself in nuts, and am sorry to add this destructive 

 Tortrix to the list of walnut insects. 



C. splendana has been sometimes abundant in the nuts in 

 this country, both in green as well as in ripe fruits. At first, on 

 examining the larvae, I came to the conclusion they were those of 

 the apple or codlin moth (C. pomonella), but in all the samples 

 of English walnuts I have examined they have turned out to be 

 the nearly-allied species, C. splendana, which also feeds on the 

 acorn and Spanish chestnut. The immature larvae I have found in 

 young fruit at the end of July and in August, on several occasions 

 at Kingston-on-Thames, one tree losing quite 10 per cent, of the 

 crop in 1892, owing to this pest. It was also plentiful at Great 

 Staughton in August, 1894 ; and a few examples have occurred 

 at Wye, Taplow, and other places in the green fruit. 



In those that I have kept the larvae lived in the nuts until 

 full-grown, when they made their exit. This took place during 

 September, and a few even in October. After a short time the 

 maggots spun a pale silken cocoon at the sides of the " cages." 

 Numbers were also found (just as we find C. pomonella) spun in 

 the crevices of the walnut bark. I called attention to this 

 species in my Eeport on Injurious Insects for 1894. 



The second species, Plodia interpunctella, Hiibn., or the 

 " Indian meal moth," is also often abundant in walnuts. So far 

 I have only had my attention drawn to it in reference to stored 

 nuts. P. interpunctella is the " maggot " that we generally find, 

 to our surprise, at dessert. Where the moth lays its eggs I do 

 not know. According to Mr. Crittenden (* Year-book' of the 

 U.S. Department of Agriculture, 1895), this larva attacks all 

 manner of stored provisions — currants, roots, herbs, figs, nuts, 

 and other commodities. These larvae I find generally, like those 

 of C. pomonella described by Mr. Adkin, and unlike those of 

 C, splendana, pupate in the nuts, in a mass of silk. This 

 Phycitid breeds somewhat rapidly in stores, five or six genera- 

 tions appearing in the year. The presence in walnuts of G. 

 pomonella is not surprising, when we consider the other Carpo- 



