Philanthus gibbosus, the hump-backed beewolf, is a species of bee-hunting wasp and is the most common and widespread member of the genus in North America.

There are very large, deep punctures on the abdomen of P. gibbosus, making the species easy and distinct to identify in comparison to other members of the genus Philanthus.

[2] While the general range of P. gibbosus size is 10–12 mm in length, females are usually closer to the smaller end of the scale.

[2] The males of P. gibbosus resemble the females very closely, but the most notable difference is the significantly reduced presence of yellow spots on the head.

The few members of the new progeny that remain continue laying eggs for another two weeks, but will die by October, likely due to changes in climate around that time.

By laying her eggs on pollen-coated bee species, the larvae are supplied with prey for nutrients instantly when they emerge.

Moreover, the nesting sites are usually centered around some sort of supporting structure, for example underneath bricks, tree roots, or cement.

[9] During the main season of its activity, May through September, the entrance to the nesting sites of P. gibbosus can be characterized by the scattered heaps of sand or soil around their supporting structure, usually bricks or tree roots.

Other oval shaped cells line the shaft which are smaller in size and contain the skeletons of other bees that were killed and fed to the larvae as nutrients.

[2] P. gibbosus is a part of a mimicry group with a wide variety of other wasps that also exhibit black and yellow banding and coloring.

[10] The colony cycle of P. gibbosus lines up with this scheduling in such a way that minimizes the amount of predation the species faces.

While P. gibbosus does not camouflage with its surroundings, it exhibits a black and yellow chitin coating that serves as a warning to other predatory species.

This coloration pattern that is characteristic of many species of wasps is a somewhat universal sign that an organism stings and should, as a result, be avoided in predation.

[7] P. gibbosus spend a significant amount of time loitering around flowers and other plants in search of insect prey to feed their young, most often bee species.

Some common species that P. gibbosus predates include the beetle Cucochodaeus sparsus and sweat bees Augochlora pura and Lasioglossum cinctipes (formerly Evylaeus arcuatus).

[2] P. gibbosus is notable in that it stings its prey in a membranous location on the ventral surface of the abdomen where the venom is quick to incapacitate many major, voluntary muscles.

The paralyzing effect of the injected venom is likely due largely in part to a block of the somatic neuromuscular transmission.

It has also been established that the venom is not limited exclusively to the natural prey, the honey bee, but also in many other insect species belonging to different orders, including spiders.

P. gibbosus then carries its paralyzed prey back to an oval cell in its nest for temporary storage until it is later used in the laying of an egg.