178 



as many earlier workers have considered. It seems probable, however, 

 that environmental conditions maj;' exert an influence by restricting 

 or encouraging metabolism and thus affecting the production of winged 

 forms ; further investigations in relation to temperature, humidity 

 and food factors, and further cytological studies, are necessary to 

 determine this. Winged viviparous females tend to produce apterous 

 viviparous females, and these to produce either apterous viviparous 

 females or a mixed progeny, including a very variable percentage 

 of winged forms. The apterous condition is to be regarded as an 

 adaptation to seasonal food and temperature conditions. The great 

 variability in the numbers of winged forms produced by apterous 

 individuals is an important point. 



The author's investigations also tend to show that the appearance of 

 sexual forms is associated with changes in the chromosome complex 

 rather than with food and temperature. It would appear that in 

 some species the sexual forms develop after a definite number of agamic 

 generations have been passed through, but this is not the case in all 

 species, as experiments with Callipierus irifolii, Mon., have proved. In 

 the case of Siphonaphis padi, L. {Aphis avenue, F.) and Toxoptera 

 graminum, Rond., in America, an extension of favourable seasonal con- 

 ditions appears to produce a corresponding extension of the agamic 

 generations, which seem to be interpolated between the winter egg and 

 the sexual generations as an adaptation to seasonal conditions. It is 

 shown in the author's experiments that certain of the apterous, partheno- 

 genetic females may carry on the parthenogenetic strain throughout 

 the winter if given favourable food and temperature conditions. This 

 cannot, however, be considered as w^holly due to these two factors, 

 because sexual forms and agamic forms appear together in each 

 generation under the same environmental conditions. 



Generalisations on the biology of the Aphids as a whole cannot, 

 however, be drawn from the study of one species, and further inves- 

 tigations on their cytology, in conjunction with breeding experiments, 

 are necessary for an understanding of their biology. 



Beeson (C. F. C). The Bee-hole Borer of Teak. A Preliminary 

 Note on the Ecology and Economic Status of Duomitus ceramicus, 

 Wlk., in Burma. (Lepidoptera ; Cossidae.) — Ind. Forest Records, 

 Calcutta, viii, pt. 3, 1921, 105 pp., 36 tables, 6 plates, 4 diagrams. 

 [Received 7th February 1922.] 



An introduction to this paper by Mr. A. Rodger gives a detailed 

 account of the previous history, distribution and economic aspect 

 of the damage caused by Duomitus ceramicus, Wlk., in Burma. Teak 

 {Tectona grandis, L.) is the only food-plant of this moth in Burma 

 and Java ; it also occurs in Sikkim, Singapore, Nias, Ceram, British 

 New Guinea and the Trobriand Islands. The geographical distribution 

 of the borer in Burma seems to coincide with the distribution of the 

 teak tree. It occurs in localities with a rainfall of 50 to 150 in., 

 and at elevations of 250-2,000 ft., but decreases in abundance towards 

 the dry zone and towards regions of high elevation and heavy rainfall. 



A full description is given of all stages of this Cossid, together with 

 its life-history, habits and natural enemies. In captivity a single female 

 will deposit 300-600 eggs in four to six days. These are usually laid 

 in cracks and imder the scales of the bark. No field records are avail- 

 able for the duration of the egg stage. The youngest larva was 

 found on 21st May. The food of the larvae is partly sap and partly 



