218 



severe. After the gregarious habit is lost, the larvae scatter so widely 

 that the damage they do becomes inconspicuous. 



There is one generation annually, the insect pupating in the autumn 

 and hibernating in the pupal stage on the ground. The moths emerge 

 in early summer, generally about the middle of June, and oviposition 

 may begin 3 days later. The eggs are laid in a broad patch of from 

 50 to 400 on the under-side of the leaf, all those of one mass hatching 

 almost simultaneously. The larvae, which pass through nine stages, 

 feed gregariously during the first four, being surface feeders during 

 the first stage. During the second stage on walnut, and the third 

 stage on pomaceous fruits, they feed at the edge of the leaf, destroying 

 everything except the stouter leaf veins. 



The insect is remarkably free from parasites, only one, Pimplor 

 pedalis, Cress., having been recorded. 



The control recommended is that of spraying with arsenicals, which,, 

 however, must be done before the larvae are in e^^dence, as in the 

 later stages they are very difficult to poison. Orchards that have been 

 thoroughly sprayed for codling moth are always free from infestation. 

 In the gregarious stages, the larvae are easily collected and destroyed,, 

 this being the cheapest and most effective way of dealing with a 

 scattered orchard infestation. In young orchards, which would not 

 be sprayed for codling moth, an application about the end of June 

 of 3 lb. lead arsenate paste to 50 U.S. gals, water would prevent 

 injury by this insect. 



HoRTON (J. R.). The Citrus Thrips. — U. S. Deft. Agric, Washington, 

 B.C., Bull. no. 616, 14th February 1918, 42 pp., 3 plates, 10 figs. 



The greater part, of the subject matter of this bulletin dealing with 

 Scirtothrips {Euthrips) citri, Moul., has already been noticed [see this 

 Review, Ser. A, iii, p. 585]. New information included deals with the 

 history and distribution of the insect, the mode of dissemination, 

 and alternative food-plants, the chief ones being pomegranate, grape, 

 California pepper tree, and apricot. Frost exercises a natural check 

 to a certain extent, but natural control by means of insect enemies 

 is a negligible factor. The most important of these is Chrysopa 

 calif ornica, Coq., the larva of which in its early stages feeds upon 

 the larvae of the citrus thrips. Climatic changes and relative in- 

 adequacy of the food supply are the chief factors influencing the 

 numbers of this thrips. 



DiCKERSON (E. L.) & Weiss (H. B.). Idiocerus scurra, Germar, a 

 a Poplar Leaf-hopper.' — Jl. New York Entoni. Sac, Lancaster, Pa., 

 XXV, no. 4, December 1917, pp. 218-224, 1 plate. [Received 

 12th March 1918.] 



Idiocerus scurra, of which I. gemmisimulans, L. & C, is a synonym, 

 is not a native American species, but was probably introduced from 

 Europe in the egg-stage on Lombardy poplar, which was the first 

 ornamental tree introduced into the United States. It first attracted 

 attention in 1916 on poplars in a New Jersey nursery and is widely 

 distributed in New Jersey on Lombardy poplar {Populus nigra italica) 

 and Carolina poplar (P. deltoides). 



