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Using Demographic and Health Survey data from 20 sub-Saharan African countries, this article compares the actual lengths of birth intervals to women's reported preferred lengths, and assesses the implications of the difference between the two for selected demographic and health indicators. The results show a clear pattern. In Comoros, Ghana, Kenya, Rwanda, and Zimbabwe, women prefer much longer birth intervals than those they actually have, compared with women in the other 15 countries studied. As a consequence, the potential effects of spacing preferences on the level of fertility and on the prevalences of short (less than 24 months) birth intervals and child malnutrition are greatest in the same five countries. The covariates of preferred birth-interval lengths are also examined. An explanation is offered for this pattern, based on the observed sharp decline in fertility recently experienced by these five "forerunners." In general, women who know, approve of, discuss, and use family planning prefer longer intervals than do their counterparts. The policy and program relevance of these results is discussed. [ABSTRACT FROM AUTHOR]

In this paper, we examine empirical evidence for a relation between infant and child mortality and fertility in Latin American countries from 1920 to 1990. We investigate the relation at several levels of aggregation and evaluate the extent to which evidence at one level is consistent with evidence at other levels. We first examine aggregate cross-country information over several decades, a type of data typically used in past research on the topic. We also examine yearly series of births, deaths, infant deaths, and socioeconomic indicators for selected countries to track the association between short-term fluctuations in fertility and infant mortality. Finally, we use micro-level data from the Demographic and Health Surveys (DHS) to assess the relation between fertility and child mortality from individual reproductive histories. The evidence we assemble from these different data sets is remarkably consistent and suggests small positive effects of infant mortality on fertility. These effects, however, may be too small to support the hypothesis that changes in child mortality are of more than modest importance in the process of fertility decline in Latin America in the late twentieth century. [ABSTRACT FROM AUTHOR]

Hymenopterous parasitoids play an important role in the control of insect populations. During oviposition, Hymenopterous parasitoids use cues such as odours from their environment to locate their specific host. Leptopilina heterotoma (parasitoid of Drosophila larvae) locate their host by probing the substrate with the ovipositor. This behaviour can be induced by the odour of the host substrate alone. We analysed the sub-lethal effects of chlorpyrifos at LD20 on the probing activity in response to a fruit odour (banana). The insecticide increased the percentage of females spontaneously probing in response to the odour. Parasitoid females were then conditioned to associate banana odour with the oviposition in host larvae. This conditioning enables parasitoids to memorize the odour and to increase their probing response to this odour. During the olfactory conditioning, females exposed to the insecticide found and oviposited in host larvae more quickly than control females. One hour after the olfactory conditioning, females exposed to the insecticide presented a higher increase of their probing response to the odour than controls. Twenty-four hours after conditioning, the stimulation produced by chlorpyrifos was no longer perceptible, but the level of response of conditioned females was still higher than that of non-conditioned females, showing that odour memory was not impaired by the insecticide treatment. These sub-lethal effects, that stimulate host searching by parasitoids without impairing odour memorization, could increase their parasitic efficiency.