307 



Grossheim (N. a.). flHMeHHafl TJlfl {Brachycolus noxius. Mordwilko.) 

 — «TpyAbi EcTecTBeHHo-McTopMMecKaro Mysen TaepuHecKaro 

 fySepHCKaro 3eMCTBa.» [Memoirs of the Xalural-HLstory Mmeion 

 of the Zemstvo of the god. of Taurida, Simferopol, iii], 1914, 

 pp. 35-78, 11 figs., 2 tables. 



It is only since 1900 that serious attention has been paid to 

 Brachycolus tioxius, Mordw., which is one of the most dangerous pests 

 of field crops. Although outbreaks of it occurred before that date, 

 it appears from a short accomit of the references to this aphid in 

 Russian literature that it was frequently mistaken for Aphis cerealis. 

 It was first described by Mokrzecki in 1900, and in that year was 

 responsible for a loss in the crop of barley in Eupatoria, government 

 of Taurida, amounting to 76 per cent, of the average. It was in 

 the same district that the author conducted observations on this pest in 

 1913. According to both Mokrzecki and Kurdjumov, B. noxius appears 

 in May, the author, however, is of opinion that it occurs much earlier, 

 but that the small number of individuals which survive the winter 

 may escape notice. The winter is passed in the egg, which is deposited 

 either on wanter-sown barley or mostly on self-so'^vni plants that are 

 largely destroyed by cattle and by ploughing in autumn and spring. 

 These aphids only rarely winter on winter-sown wheat. Although very 

 few colonies of hce were foimd on 16th June and the number in each 

 colony was small, both these figures increased greatly after the 21st of 

 that month. While the numbers are small they live at the base of the ear 

 or inside the sheath of the covering leaf. Later, when the crops ripen 

 and the numbers increase, they concentrate on the green parts of the 

 plant, on the tip of the ears, or as low down as the first node of the 

 stem. In the middle of June the colonies consist of adult partheno- 

 genetic wingless females, larvae of various stages, nymphs and winged 

 colonising females, all these stages being described and figured. The 

 excreta and remains of the wingless forms, which pass all their life 

 inside the tube, drop down to the bottom of the sheath and decompose, 

 filhng up, in the case of large colonies, the whole of the tube. It was 

 not possible to ascertain the duration of Hfe in nature, but in captivity 

 the wingless individuals lived 15 or 16 days and the winged ones 12 to 

 14 days. The migration of the winged adults takes place usually 

 during the morning hours, and it is thought that they may be 

 carried by wind over several miles. The first individuals were 

 observed on winter-sown wheat and the migration to barley started 

 after 21st June, their numbers on the latter plant increasing daily. 

 The chief damage is done in June, affecting both the form, colour 

 and time of ripening of the crop. The damage to wheat is less 

 than that to barley, owing to the aphids appearing in large 

 numbers only when the wheat is already well developed and the 

 ears have partly emerged from the sheath. Barley is attacked at 

 a time when it is miable to withstand the pest ; the development of 

 the ear is delayed and the upper two or three leaves often do not unfold 

 at all. Thus damage amounts to either .the total loss of the harvest, in 

 case of yoimg barley, or to a considerable decrease in the case of wheat 

 or older barley. At the end of June, when the grain is nearly mature, 

 the increase of the aphid is at its height. With the ripening of the 

 plants the conditions become less favourable and the numbers drop 



(C161) c2 



