Diapause Behaviour Research Articles

The reproductive biology and diapause of the British fungal‐breeding Drosophila

Abstract. Seasonal reproductive development was investigated in four obligate fungivorous species, D.phalerata Meigen, D.transversa Fallen, D.cameraria Haliday and D.confusa Staeger. Samples of females taken from woodlands over a 2 year period were scored for reproductive status and fat content. Populations of D.phalerata and D.cameraria maintained in an outdoor insectary provided information on developmental time and adult mortality throughout the year. Experiments in controlled environmental chambers gave percentage diapause curves against day length for all four species. In D.phalerata the influence of temperature and fungus upon diapause behaviour was also investigated. In D.phalerata the optimal strategy for reproductive development can vary from month to month. Maturation of females may be immediate, dependent upon a fungal cue or completely prevented.

Relict diapause in an introduced weevil in New Zealand

The Argentine stem weevil Hyperodes bonariensis Kuschel, a stem boring weevil native to the southern part of South America, was first reported in New Zealand in 19271 where it has become a widespread and serious pest of Graminae. Recent investigations2 have demonstrated the existence of reproductive hibernatory diapause induced by a critical photoperiod in the population in Canterbury, New Zealand (latitude 43°39′S). Coincidentally, it was noted that similar ovarian diapause occurs in H. bonariensis found at a corresponding latitude (41° S) in the Bariloche region of Argentina3. Owing to the imminence of the autumnal equinox at diapause induction (early March in both localities), identical daylengths are experienced successively over a wide latitudinal range within a week. In the present report, examination of the New Zealand population at this time, sampled over at 8° range of latitude, revealed a corresponding synchronous induction of diapause without the usual latitudinal and therefore temperature-related shift in critical photoperiod4. This lack of temperature-related shift and the relatively mild winters suggest that the diapause behaviour of H. bonariensis throughout New Zealand is an adaptively inappropriate relict response resulting from the recently arrived weevils cueing into the same photoperiodic seasonality as their South American counterparts, which in regions such as Bariloche, must have evolved diapause behaviour to survive.

Effects of Photoperiod and Temperature Regimens on the Biology of European and United States Alfalfa Weevil1 Populations2

The different responses of populations of the alfalfa weevil, Hypera postica (Gyllenhal), from Europe and from the eastern and western United States to temperature and photoperiod indicated that European and Western United States populations are more closely related than European and eastern United States populations or western and eastern United States populations. This conclusion was based on feeding and diapause behavior of adults after larvae were reared under the various regimens. When reared under 8 h photophase, adults from Europe and from the western United States fed for a shorter time following emergence and entered extended diapause; the opposite was true of adults from an eastern United States population. Differences occurred in larval and pupal development time, larval survival, and adult emergence rates of the 5 different populations.

The accumulation of piperidine in the central ganglia of dormant snails

During a 2-month period of experimentally induced hibernation (diapause), piperidine content in the snail central nervous system increased to 5 times the amount found in active snails. A higher rate of piperidine synthesis in the brain of dormant snails than in controls is inferred (a) from opposite gradients for endogenous and tritiated piperidine between the blood and brain tissue, and (b) from the highest conversion of piperidine precursors in the brain. A possible involvement of piperidine in controlling the diapause behavior is suggested.