To make this educational video, some stalwart soul offered themselves as food for a horsefly of the genus Hybomitra. Like mosquitoes, only female horseflies drink blood, and they do so so with fearsome mandibles that contain six sharp blades, or stylets. Here’s a picture by Anthony Thomas of the mandible of a Hybomitra affinis horsefly, showing the stylets(“st”), and below that, one of the stylet blades.
Blood-feeding is accomplished by retracting the labella, the two lobes at the base of the labium [“la” in first picture above), to expose the fascicle of stylets. The long flattened sharp blades of the Mandibles (Fig. 5) are the first of the stylets that enter and cut through a vertebrate’s skin. With its body firmly anchored to the hosts skin/fur/feathers/scales the female fly thrusts its head downwards forcing the mandibles into flesh. Muscles attached to the base of the mandibles move the blades in a side-to-side scissor-like action thus enlarging the initial wound.
And some Fun Horsefly Facts from Wikipedia:
Tabanids are agile fliers; Hybomitra species have been observed to perform aerial manoeuvres similar to those performed by fighter jets, such as the Immelmann turn. Horseflies can lay claim to being the fastest flying insects; the male Hybomitra hinei wrighti has been recorded reaching speeds of up to 145 km (90 mi) per hour when pursuing a female.
In the video below, the bite itself takes place 54 seconds in, and then the hungry lady fills up with blood that will be turned into eggs. I bet you’ll wince a little watching this!
And the YouTube notes:
Hybomitra horse-flies biting and sucking blood. Camera: Canon Powershot SX200 with a +12 diopter close-up lens (a doublet lens from an Elmo Super 8 camera).