A Bandit’s Foot

What am I looking at?

This is the foot, or tarsal pad, of a robber fly, followed by several of the tarsal segments (also called tarsomeres) that make up the final segment of a robber fly’s leg. You can see spiky bristles along the leg (1); adhesive, Velcro-like pads covered in flexible, hair-like setae (2); and two hooked claws at the end of the foot (3) – all of which help robber flies catch and grasp other insects.

Click on the right arrow to see an alternate view of the end of a robber fly foot.

Biology in the background

Robber flies, also called assassin flies, are in the family Asilidae and live all over the world (except Antarctica) and feed almost exclusively on other insects. They have multiple gripping mechanisms built into their legs and feet that allow them to catch and hold their prey as they hunt and feed. They ambush predators, letting other insects approach as they hide, perched on a secluded twig or log, and then take off when a prey insect comes in range. Once they catch their prey, they inject a paralyzing saliva to prevent the prey from struggling and potentially injuring the robber fly while it feeds. The saliva also contains digestive enzymes that liquify the soft tissues of the prey insect.

Robber flies vary in size a great deal, but some species can grow up to 5 centimeters long, or roughly 2.5 times the width of a human thumbnail.

Technique

This image was created using confocal microscopy.