180 



of the beetle synchronises with that of the rainfall in the first few weeks 

 of the monsoon. In a wet year 75 per cent, of the beetles emerge 

 in the first month of the rains ; in a dry year the period is prolonged 

 to six or eight weeks. Similar work on the emergence periods is being 

 done with other species of borers. It is believed that the control of 

 borers of this class will be obtained by modifications of the felling 

 and seasoning rules. 



Teak borers include Duomitus ceramicus (bee-hole borer), Haplo- 

 hammus cervinus, Phassus malaharicus , etc. Investigations on the 

 bee-hole borer, which is the most important, are recorded in detail 

 in the preceding abstract. 



HusAiK (M. A.) & Bhasin (H. D.). Preliminary Observations on 

 Lethal Temperatures for the Larvae of Trogoderma khapra, a 

 Pest of Stored Wheat. — Rept. Proc. 4th Ent. Meeting, Pusa, 

 February 1921, Calcutta, 1921, pp. 240-248, 1 plate, 2 charts. 



The two problems that require to be solved for the successful storing 

 of grain are the rendering of it free from all stages of insect life before 

 storage, and the keeping of it free from insects when stored. The 

 methods devised for these purposes include processes which aim at 

 accomplishing both of these objects by means of a single operation. 

 Under this heading come the use of naphthaline balls, of castor oil 

 and other oils, of mercury, the mixing of sand with the grain or covering 

 the grain with a uniform layer of it, and the hermetical sealing of 

 the grain. This last method, if found successful, should be the simplest 

 and best for grain storage. In a second category are those processes 

 in which the grain is first subjected to treatment to free it from 

 infestation, and is then kept in insect-proof stores. These include 

 fumigation, mechanical separation of the insects from the grain, 

 and superheating. All these methods are briefly reviewed, the author 

 pointing out that there is at present no really satisfactory method 

 that can be recommended generally, especially for grain in bulk. 



An instance of the difficulty of treatment is the elevator at Lyallpur, 

 containing 32 bins, eight of which have a total capacity of 2,938 tons. 

 Wheat in this elevator was found to be infested with Trogoderma 

 khapra at the top and with Rhizopertha dominica at the bottom of 

 the bins. Though the temperature of the bins filled with wheat was 

 found to rise as high as 113° F., the insects remained unaffected. 

 It has been stated that a temperature of 110° F., maintained long 

 enough to penetrate the tissues of the insects, kills all grain pests, 

 but it would appear that insects in the tropics, which are accustomed 

 to high temperatures, can stand excessive heat better than those in 

 cooler regions. 



In view of these considerations, experiments were undertaken with 

 the larvae of T. khapra, the commonest wheat pest in the Punjab 

 and the one of which the larvae are most resistant to high temperatures. 

 The apparatus devised for exposing the insects to varying temperatures 

 is described and the results recorded. At 185° to 212° all insects 

 were dead after 30 seconds ; at 122° all were dead after five hours, with 

 proportionate periods for intermediate temperatures. The effects 

 of various high temperatures on the germinating capacity of wheat 

 of different types are discussed ; all types tested gave 100 per cent, 

 germination after 15 to 20 minutes exposure to 212° F. 



