Observations on the heating of grain caused by insects

1. The heat output by the insects, Oryzaephilus surinamensis, Tribolium confusum, Sitophilus zeamais and Sitophilus granarius, was investigated by reading the temperature of the inside of the grain in which the insects were developing in 2 Ib or 7 Ib jars incubated at R.H. 2. All the insects tested increase the temperature of grain, but the amount of heat produced by insects varies with the species of and the developmental stages of the insects. 3. It was found that all the temperature peaks correspond with the peak in number of the fourth instar larvae and the period in which the insects start to cause the heating corresponds to its 1 st and 2nd instar larvae. 4. Sitophilus spp. whose larvae live in the endosperm of the wheat produced more heat than Tribolium confusum and Oryzaephilus surinamensis whose larvae live on the grain. 5. Among the four species of insects, Sitophilus zeamais Produces the highest heat, followed by Sitophilus granarius, Tribolium confusum and Oryzaephilus surinamensis. 6. It is considered from the above results that the heat produced by insects seems to depend upon the species, the number and the age structure of population, and its its surroundings. 7. It is suggested therefore that when comparing the rate of development of insects kept at different densities. the effects caused by heating at the higher densities must be considered.