INFLUENCE OF CONSANGUINITY ON THE SEX-RATIO AND DIAPAUSE OF DIPRION-PINI L (HYM, DIPRIONIDAE) POPULATIONS .2. EFFECT OF INBREEDING ON DIAPAUSE

Experiments were undertaken in 1990 and 1992 to prove the effect of co nsanguinity on diapause and to study its links with sex determinism an d possible genetic factors. These experiments were realized on the pro genies of colonies collected in Fontainebleau forest. From adult emerg ences in April different ways of breeding were comparatively carried o ut during two generations: inbred brother-sister crosses, non-inbred c rosses with insects from another origin, in particular with a referenc e rearing strain reared for many generations; and breedings of virgin females. The progenies of these crossings were reared in the same stan dard laboratory conditions favourable to development without diapause (16 degrees C, 15 h L-9 h D photoperiod for the young larvae, 20 degre es C, 16 h 30 L-7 h 30 D thereafter). Diapause rates and sex-ratio wer e simultaneously observed. The results show an important increase in d iapause rates and male rates in the progenies of inbred insects. We al so found a link between sex and diapause, its rates being higher in ma les. On the other hand, crossings with the rearing strain corroborate the existence of a genetic factor strengthening diapause which would b e eliminated in reared populations if only the without diapause insect s are bred from generation to generation. Some hypotheses about the in teraction between consanguinity, sex determinisms and the existence of this genetic factor are drawn from these results. It is suggested tha t these phenomena may have a noticeable importance for population dyna mics ofD. pini.