REPORT OF TEE ENTOMOLOGIST 227 



SESSIONAL PAPER No. 16 



ture of -21 degrees F. The females become active in the spring, probably as soon as the 

 snow disappears and the eggs then begin to develop. The length of the egg state in 

 the spring is from ten to fifteen days and in the summer from four to seven days. 

 The larvae are similar in general form to the adults. The length of the larval stage 

 \ aries from two weeks in the early spring to about four days in midsummer. Tbe 

 first winged adults appear in May or June. The whole life cycle occupies from twelve 

 to thirty days. 



Korolikoff* has recently investigated several species of thrips injurious to cereals 

 and grasses in Russia in the neighbourhood of Moscow. He found that the insects 

 passed the winter in the green, soft tissues in the leaf sheaths of young plants, and 

 when the spring comes they migrate to the early cereals and later to the summer crops. 

 Their injuries to' plants are caused chiefly by the fact that they feed up»n the juices 

 of the different parts of the flowers, and especially on the ovary, that is, in the cereals, 

 the young grain. They migrate from one species of plant to another, for example, from 

 rye to wheat and oats. He recommends the destruction of weeds, especially those 

 belonging to the families Leguminosse, Gramineae and Compositae, and the sowing of 

 what one may term ' bait ' crops such as rye or oats round the fields under cultivation. 

 This should be done a fortnight before the time of sowing the winter cereals in order 

 to attract the insects and afford them shelter when the crops are coming up. When 

 the ' bait ' crops are removed later, a large number of the thrips are removed also. 



The various species of thrips appear to hibernate where they have been feeding : in 

 the stems of grains which have died down, in crevices in the ground or under rubbish. 

 In the case of species infesting cereals and grass crops they can be attacked only by 

 the adoption of cultural methods. The hibernating stage is the most convenient stage 

 of their life history to combat them. The burning of the grass or stubble in the 

 J 'all and, either as an additional measure or as an alternative, the deep ploughing of the 

 soil, will result in the' destruction of a large portion of the hibernating individuals. 

 Grain which has been infested should be cut as early as possible in the spring to 

 remove the individuals recently emerged from hibernation before they have reproduced 

 in any considerable numbers. After threshing, the screenings and chaff which contain 

 large numbers of the insects, should be burnt. 



THE WHITE-MARKED TUSSOCK MOTH (Hemerocampa leucostigma S. and A.) 



This insect was extremely abundant in certain places in Ontario, New Brunswick, 

 Nova Scotia and Prince Edward Island during the summer of 1910. In the cities of 

 Halifax, N.S., and Charlottetown, P.E.I., and Kingston, Out., its defoliation of the 

 shade trees, well known in Toronto, caused the citizens some alarm. In Charlottetown, 

 T found on examination that the larvae had been fairly well parasited, and to some 

 extent also in Halifax. Further observations on collected material indicate the same 

 fact. It is not improbable that the outbreaks will be checked by natural means, but 

 the uncertainty of the operation of such natural controlling agencies as the experience 

 of the insect in Toronto exemplifies, necessitates the employment of thorough eradica- 

 tive measures in cities where the value and importance of shade trees is unusually 

 great. 



Life history. — During the winter the conspicuous white or creamy-white egg 

 masses having a frothy appearance may be found on the trunks and branches of trees, 

 on fences and other places to which the caterpillars crawled when full grown. The 

 young caterpillars hatch out at the end of May or early in June, and become full 

 grown towards the middle or end of July. The mature caterpillar is distinct in form 



* Korolikoff, D. M., ' Tripsi jivoustchie na. nacikh Slakakh.' Lsviestiia Moskowskago 

 Splskhosiaistvennnago Instituta. (Annals of Agron. Inst. Moscow), Vol. 16, pp 192- 9 01 

 Moscow, 1910. 



16—154 



