Temperature Relations of Teneral Development and Behaviour in Aphis Fabae Scop

Abstract

1. The teneral stage in Aphis fabae Scop. is defined as the interval between eclosion of the alate imago and flight when flight is not extrinsically activated or inhibited. 2. In field marking experiments the teneral stage is shown to be usually development-limited, not behaviour-limited, by its relationship to temperature. 3. It is suggested that the logistic curve fits the rising temperature x development-velocity curve because this is a statistical distribution like the Pearson type 1. 4. The logistic curve is fitted to teneral period in naturally varying temperatures by a method of successive approximation. 5. In trapping experiments take-off is inhibited by light below c. 100 f.c. and by temperature below c. 16° C. at 1 ft. in a bean crop. 6. These behaviour responses sometimes lengthen the apparent teneral period. 7. The results are confirmed in the laboratory at constant and at varying temperatures. 8. This also confirms that temperature changes per se even over a range of c. 7-34° C., and other climatic factors, have negligible effect on rate of development during the teneral period. 9. Individual variation is a constant proportion of teneral time at all temperatures. 10. In laboratory experiments the same criteria apply to Aglais urticae L. 11. This period of inactivity warrants further examination in an ecological context.