Temperature and water relations of a parasitic wasp in its free-living adult stage and its phytophagous host

Abstract

1. 1. Temperature and water relations in the parasitic wasp Anaphes ovijentatus (Crosby and Leonard) (Mymaridae: Hymenoptera), one of the smallest of insects, and its host Lygus hesperus Knight (Miridae: Heteroptera) were studied. 2. 2. LT 50s for the free living adult female wasps were higher (20.63 hr) than those of male wasps (14.68 hr) and 1st instar Lygus nymphs (7.07 hr) at 30°C with an RH of < 5%. 3. 3. Critical thermal maxima were significantly higher in the parasitic wasp (47.6°C) than in its host (45.7°C). 4. 4. Rates of water loss were dependent upon temperature and saturation deficit with evidence of an ability of both species to exercise some control over loss rates under increasingly stressful conditions. 5. 5. Rates of water loss of both species were comparable to those of other xeric-adapted insects on a loss per unit of surface area-specific basis. On a weight-specific basis, rates of water loss for these insects which weigh less than 100 μg were higher than those of larger, xeric-adapted species.