Effect of temperature and photoperiod on the life cycle in lineages of Myzus persicae nicotianae and Myzus persicae s. str. (Hemiptera: Aphididae)

Male production was examined in 70 Myzus persicae s.str and M. persicae nicotianae clonal lineages at 17 degrees C and 10L : 14D. Sixty nine were characterised by a partial loss of sexuality (androcyclic producing few males,. and intermediates producing some males and mating females), and one was found to be permanently parthenogenetic. High within and between lineage variation was detected. Most (81%) of the clonal lineages produced few males (0-5 males per parent) and only 6% had male production (10-16 males per parent) comparable to that (12-23 males per parent) of seven lineages with a sexual phase (holocyclic) which were examined under the same conditions. The length of prenatal exposure to 10L : 14D increased the production of males. Continuous rearing under 10L : 14D at 12 degrees C adversely affected male production in another intermediate clonal lineage. Temperature was found to affect the production of sexuals and to modify the short day photoperiodic response. The production of males and mating females was higher at 12 degrees C than at 17 degrees C in most of the 20 aforementioned clonal lineages with a partial loss of sexuality. Six lineages were permanently parthenogenetic at 17 degrees C, but two of them produced a few males and the other four a few males and mating females at 12 degrees C. Seven lineages which produced a few males at 17 degrees C, also produced some mating females at 12 degrees C. Lastly, photoperiod similarly affected the production of sexuals in two of the aforementioned clonal lineages, one with a sexual phase and one intermediate, although the regimes for the peak of sexuals were different. In both lineages, however, males appeared in a 0.5-1 h shorter scoto-phase than mating females.