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The reproductive sequence of sexuparae of the sycamore aphid, Drepanosiphum platanoidis (Schrank) (Homoptera: Callaphididae), observed in the field and glasshouse was examined to elucidate the relationship between host nutrition and sex ratio. The observations were made in autumn when the transition from parthenogenetic to sexual reproduction occurred. A switch occurred in the reproductive sequence of the sexuparae. The production of apterous sexual females (oviparae) was followed by alate males, after a brief reproductive pause lasting 2.5-4.0 days. The switchover period was relatively constant across treatments and years. On poor hosts, the first appearance of the oviparae was a day later, whereas the first appearance of males was a day earlier than those on good nutrition. The primary sex ratio (i.e., proportion of males) was numerically female biased. Under semi-natural field conditions it was 0.22, but altered to 0.18 and 0.29, respectively, under poor and good host nutrition in the glasshouse. In both the field and glasshouse, nymphal development time was significantly longer in oviparae (ca. 22 days) than in males (ca. 18 days). The time from birth to adult was significantly shorter on good hosts (oviparae: 20 days; males: 17 days) than on poor hosts (oviparae: 23 days; males: 19 days). The proportion of nymphs surviving to the adult moult was not dependent on sex in both the field and glasshouse, but the chances of survival were slightly enhanced under good (88%) compared with poor (82%) host nutritive status. In conclusion, the order of morph production and differences in maturation times ensured the synchronisation of the sexes so that mating and oviposition opportunities were optimised before the onset of winter. The female-bias in the sex ratio maximised the fitness of sexuparae, and reduced the chances of local mate competition by economising in members of the competing sex. © 2005 The Netherlands Entomological Society.

Original publication

DOI

10.1111/j.1570-7458.2005.00257.x

Type

Journal article

Journal

Entomologia Experimentalis et Applicata

Publication Date

01/05/2005

Volume

115

Pages

311 - 321