Physocephala tibialis is a species of thick-headed fly (family Conopidae) found throughout the eastern United States, often near flowering plants.

P. tibialis flies parasitize many different species of bees by laying their eggs inside the abdomen of their host.

[10][8] When a bee becomes parasitized by a P. tibialis larva, certain behaviors such as induced grave digging[11] and changes in flower preference[5] often occur.

[5] The larva is white and swollen when it hatches from the egg and molts three times until it reaches its fully grown size of around 30–60 mm in length.

[10] The adult P. tibialis is characterized by an almost entirely black abdomen and pale tarsal segments on the legs.

[13] The lateral areas of the head are light yellow, and the segment connecting each half of the face is black.

[13] Flies from the family Conopidae have thick ptilina, sacks on the head that can be inflated to break through the puparium wall.

[8] The growth and development of P. tibialis is fairly unique in that a single egg is laid inside of a Hymenopteran host.

[10] P. tibialis flies, along with a few other Conopidae species, lay their eggs inside bees and wasps (order: Hymenoptera).

[9] P. tibialis females can often be found near the base of flowering plants anticipating the arrival of host species.

P. tibialis larvae have different likelihoods of inducing self-burial behavior depending on the species of the Hymenopteran host.

[16] Bumblebee hosts often choose to pollinate different selections of flower species after being parasitized by P. tibialis.

The fly then rhythmically inflates and deflates the ptilinum to continue maneuvering its way out, using its mouthparts and legs as leverage to pry itself from the corpse.