570 



so seriously infested that the crop is not worth harvesting, they are 

 ploughed in, thus giving the pest an opportunity of completing its life- 

 cycle. Crop rotation and autumn ploughing are not practised by many 

 commercial onion-growers, though the latter method would expose 

 many puparia to the sun and to natural enemies, such as birds and 

 Carabid beetles. Experiments in the control of the adult during the 

 preoviposition period showed that a poison consisting of 28 grains 

 sodium arsenite, 1 U.S. gal .water and | pt. molasses killed the flies within 

 one day. In the field, the first application of the spray was made 

 on the 10th July. Thorough spraying was found to be unnecessary, 

 since the diluted molasses attracted the flies. Four applications were 

 made to control the second brood, the bait being renewed once each 

 week. The results obtained in an isolated field were encouraging, but 

 the effectiveness of the spray against the first brood in non-isolated 

 fields remains to be tested. Specimens of Tritoxa flexa, Wied. (black 

 onion fly), were captured on 27th August. Chaetojms aenea, Wied. 

 (barred-winged onion fly), was bied from decaying and smut-infested 

 onions. Euxesla notata, Wied., was reared from similar onions and 

 from decaying onion leaves. The larvae were frequently found together 

 with those of H. anfiqua. The first noticeable injury caused by Thri])s 

 tabaci, Lind., was observed at the end of June, when the thrips were 

 abundant between the two central leaves ; in August the leaves bad 

 a whitened appearance produced by the attacks of the insect. Agrotis 

 (Noctua) c-nigmm, L., and Lycophotia margaritosa, Haw. {Peridroma 

 saucia, Hb.) caused slight injury in some districts. The former 

 species was highly parasitised by Apanteles sp. The following insects 

 were occasionally observed : Ceramica {Mamestra) 23icta, Harr. 

 (zebra caterpillar), Diacrisia virginica, F. (yellow bear caterpillar), 

 Celerio {DeilepMIa) lineata, F. (white-hned sphinx), Lggus -pratciisis, L. 

 (tarnished plant-bug), and Diabrotica l2-punctata, Oliv. 



MozNETTE (G. F.). Notes on the Brown Lace-Wing {Hemerobiiis paci- 

 ficus, Bks.). — Jl. Econ. Entom., Concord, viii, no. 3, June 1915, 

 pp. 350-354, 1 plate. 



Hemerobius pacificus, Bks., is of considerable economic importance, 

 in that it is predaceous in its larval stage on Acariiia, Aphididae and 

 other soft-bodied insects. It destroys the oviparous females of Aphis 

 sorbi, Kalt. (rosy apple aphis) and of Myzus ribis, L. (currant aphis). 

 During July 1913, it was abundant in hop yards, feeding on the wingless 

 females of the summer generation of Phorodonhumidi, Schrank, and on 

 Tetranychus telarius, L. (red spider). It has been recorded from 

 Oregon, California, Washington, New Mexico, Arizona, and British 

 Columbia. On 3rd November 1913, eggs and larvae were found 

 among colonies of A. sorbi on apple trees ; most of the eggs were 

 deposited on the lower surface of the leaf next the midrib, lateral vein, 

 or in the axil of the two. Eggs laid on marked leaves on 1st December 

 1913, hatched out under artificial conditions 9 days later. The larvae 

 of H. piacificus developed more rapidly in warm than in cool weather ; 

 the average larval period was 14 days. The food supplied consisted 

 of A. sorbi, Kalt., Macros ipkum ly coper sici, Clark, and Rhopalosiphum 

 {AmpiJiorophofa) lactucae, Kalt. Pupation usually took place in 

 crevices of the bark, occasionally in the curled leaves of the apple. 



