OXYGEN-CONSUMPTION OF THE EGGS OF 4 NONDIAPAUSING BLACKFLY SPECIES (DIPTERA, SIMULIIDAE)

The respiration of the eggs of the 4 non-diapausing blackfly species Simulium erythrocephalum (De Geer 1776), Simulium ornatum (Meigen 1818), Simulium morsitans Edwards 1915, and Simulium equinum (Linnaeus 1758) was studied, using a Twin-Flow-Micro-respirometer. All species were studied at 21 degrees C. Additionally, S. morsitans was studied at 18 degrees C and S. erythrocephalum at 14 degrees C. The respiratory rates vary species specifically in correlation with the egg phases: from laying until phase 3A they increase, during phases 4 and 5 they remain almost constant, and shortly before hatching they increase again. Only in S. ornatum the oxygen consumption keeps increasing also during phases 4 and 5. The lowest respiratory rates are found in S. equinum (36 pmolO(2)/h/10(-3) mm(3) in phases 4-5), the highest in S. erythrocephalum (68 pmolO(2)/h/10(-3)mm(3)). S. morsitans is intermediate (45 pmolO(2)/h/10(-3) mm(3)), and S. ornatum has initial values slightly above those of S. equinum, but finally reaches the same level as S. erythrocephalum. All respiration values were calculated for the initial egg volume directly after laying. At lower temperatures, the respiratory rates decrease in correlation with the prolongation of development. The total oxygen consumption calculated over the entire development is about equal in S. erythrocephalum and S. morsitans and independent of the incubation temperature. An oxygen summation rule is suggested on the assumption of consistent total oxygen needs of the eggs of each species at different temperatures. The ecological factor oxygen supply appears to be as important for the egg development of blackflies as the factor temperature.