Tabanus longiglossus is known for the painful bites that it and other horsefly species inflict.  Fascinatingly, only the females inflict these bites while the males feed on the nectar and occasionally pollen of flowers.  The females require meals of blood in order for them to reproduce.  Females of this species, as well as other species of horseflies, feed on various vertebrates (Grimaldi and Engel 2005).  They are most well known for feeding Closely related female specieson mammals but they may feed on birds, reptiles, or amphibians as well.  Sometimes they have attacked herds of dairy cattle so viciously that they significantly reduce their milk yields (Resh and Carde 2003).  Most people are familiar with the nuisance of their presence, leaving painful, itchy bites that can result in substantial blood loss.  When in search of a blood meal the females land on a victim just out of reach so they can’t be swatted away.  After they land they create a laceration on the host’s skin with their serrated, blade-like mandibles and maxillae (this is why their bites are so painful) as opposed to say, mosquitos that puncture the skin of their host to retrieve blood.  Once the blood begins to pool either under or on the host’s skin Tabanus longiglossus goes to work soaking it up with their extended labella.  When they have retrieved all the blood they need they fly away leaving a bloody wound (Grimaldi and Engel 2005).  If the fly is infected with a disease a bite can pass it to the victim (Resh and Carde 2003). More information on the diseases that Tabanus longiglossus you can go to the interactions page of this website.  As mentioned previously, the males do not feed on blood and lack mandibles, the mouthparts necessary to do so.  Due to the fact that they only frequent flowers they are rarely seen (Arnett 1985).  Once their food is ingested it passes through a fully functioning gut just as all other Arthropods.  The food is stored in the crop until it is passed through the rest of the gut.  They also have an open circulatory system like other insects do (Hickman 2012).