Blood and sugars are needed to nourish deer flies and horse flies

During a study carried out in Connecticut on the feeding of horse-flies [Tabanidae] and deer-flies [Chrysops spp.], 2559 specimens were examined, of which 271 (10.6%) had partial blood-meals. The majority of these were from cattle, but deer, dog, horse and rabbit blood was also found. It was also found that females of 33 inland and 3 coastal tabanid species fed on nectar sugars as well as on vertebrate blood. Subsequent laboratory experiments showed that female tabanids that ingested both blood and sugar lived 2-3 weeks longer than those fed on blood and distilled water. In other tests, females that had fed on sucrose solutions but were not given blood lived as long as those that had taken blood and sugar meals.