Digestive processes of hematophagous insects VIII. Estimation of meal size and demonstration of trypsin in horse flies and deer flies (Diptera: Tabanidae)

In this further paper of a series [see RAE/B 63, 1977, 1984, etc.], blood-meal sizes are given for 2 species of Chrysops and 10 of Hybomitra collected in central Alberta in a Manitoba trap and also reared from collected larvae. All were fed on man or rabbits in the field or in the laboratory on beef blood. In each species, the average amount of blood ingested by the females was approximately equal to their average unfed weight. However, there was no significant intraspecific correlation between the unfed weight of a female and the amount of blood ingested. Females of H. affinis (Kby.), H. arpadi (Szil.) and H. lasiophthalma (Macq.) took larger meals when they fed on man than when they fed on rabbit or on defibrinated beef blood through a Silverlight membrane. Under certain circumstances, the diverticulum was used as a reservoir for blood. Trypsin was demonstrated in 13 species (5 of Chrysops, 7 of Hybomitra and Haematopota americana O.-S.). In H. affinis kept at 25 deg C, the maximum amount of trypsin occurred 24 to 48 h after ingestion, and there was a significant correlation between trypsin activity and protein content of the mid-gut.