96 



increase of the beetles in the general area or to the starting or extension 

 of an epidemic of beetles. On an area of about 48,000 acres of badly- 

 infested pine forest, a count of young and matured beetles that 

 developed in an average foot of bark, and of the exit-holes, showed 

 that there is a notable decrease in numbers during the development 

 of the broods each year on account of the increase of natural enemies 

 and other disturbing factors. This offers some explanation of the 

 epidemics of beetles that rise and fall within a limited period, and why 

 the western yellow pine forests are naturally protected from total 

 destruction. While many beetles die in their earlier stages, normally 

 an average of 150 beetles to the square foot of bark develop into 

 adults in a case of average infestation, and since it requires an average 

 of about 10 beetles to the square foot to kill a vigorous, healthy tree, 

 it is obvious that all the pine timber of the western forests would soon 

 be destroyed if it were not for natural and artificial control. Destruc- 

 tion of timber by insects can largely be prevented by cutting the 

 trees in late autumn and early winter and piling the wood loosely 

 until it is thoroughly dry. Damage to posts can be prevented by 

 laying them on the ground where they will receive the full force of 

 the sun, and turning them occasionally so that the young stages of 

 the borers will be killed by the heat. Attention has lately been drawn 

 to several instances of beetles damaging lead [see also R.A.E. , A, viii, 81], 

 A particularly serious instance occurs in California, where a wood- 

 boring species is able to throw hundreds of telephones out of order 

 by boring holes in the cables through which water can enter, rendering 

 the connections useless. It has been found that for the control of 

 wood-boring insects chemical substances are very seldom as effective as 

 management in logging and manufacture to render the bark and 

 wood unfavourable to attack. For example, one of the most destruc- 

 tive species of termites cannot live if deprived of moisture in ground 

 or foundation timber. 



The work for the suppression of the gipsy moth [Porthelria dispar] 

 and brown-tail moth [Nygmia phaeorrhoea] during the year is reviewed 

 [R.A.E. , A, vii, 60, 103, 104, 176, 341]. Investigations into the spread 

 of the parasites showed that Schedkis huvanae could not survive the 

 winter in New Hampshire, and was scarce in Massachusetts ; Anastatus 

 bifasciatus showed better results ; large colonies of each have been 

 liberated in the autumn. The situation with regard to the parasites, 

 Compsilura concinnata, Blepharipa scutellata, Apanfeles melanoscelis 

 and Calosoma sycophanta is discussed, no remarkable change having 

 occurred in their status since the previous report. Nygmia 

 phaeorrhoea, while confined to a smaller area, increased slightly in 

 numbers in the Eastern part of the territory. Apanteles lacteicolor 

 was present in small numbers in about 10,000 larvae examined ; 

 Meteorus versicolor was much less abundant. The commonest parasite 

 found in these collections was Zygobothria nidicola, about 20 per cent, 

 of the caterpillars being parasitised by it. 



The extension and demonstration work carried out during the year 

 is described. The use of powdered lead arsenate or calcium arsenate 

 against the cotton boll weevil [Anthonomus grandis\ which was 

 advocated in last year's report, is being greatly extended with 

 promising results, but care is required in its application and instructions 

 are being distributed for this purpose. As a remedy against the moth 



