Native Bee Parasites — Wasps

Installing bee houses and hotels are great ways to encourage nesting, protect pollinators, and educate communities about bees' vital role in food production and ecosystem services. Unfortunately, productive bee nests are loaded with pollen, nectar, and bee larvae, making them a smorgasbord of food resources for pests and predators!

  Native Bee Nest Monitoring

Nest monitoring and maintenance are essential to maintaining bee health. Fortunately, proper care can significantly reduce the incidences of pests and parasites and allow managed bees to thrive. This article highlights the common enemies of mason bees and leafcutter bees and methods for their control.

  Types of Parasites

  Parasitism By Theft

A cleptoparasite is an animal that steals food or prey from another animal. For bees, most cleptoparasites lay their eggs inside bee nests and the larval parasites eat the pollen loaves intended for immature bees. Some cleptoparasites will even eat the developing bees in the process.

  Parasitism By Body Snatching

Predatory and parasitic wasps are among the most common enemies of cavity-nesting bees, including mason bees. Sneaky females invade nests through small openings or weak spots in the nesting materials or through incomplete or uncapped nesting holes. They use their needle-like ovipositor to paralyze the bee larvae by inserting it through the cocoon wall. Upon hatching, the wasp larvae kill and eat the bee.

  Wasps

  Chalcid Wasp

Type of Parasite: Body Snatcher

Species are widespread throughout North America, and all are metallic green, blue, or black, with red eyes, and are 5/64 to 5/32 inch in length (approximately 2 to 4 millimeters). Males are slightly smaller than females.

Chalcid wasps are some of the most destructive parasites of mason and leafcutter bees. The sneaky female wasp invades nests through small openings or weak spots in the nesting materials or through incomplete or uncapped nesting holes. They use their needle-like ovipositor to paralyze the bee larvae by inserting it through the cocoon wall.

Females can attack multiple cocoons, so loose cocoons are particularly susceptible and must be protected! After paralyzing the bee larva, the female lays 10 - 50 eggs inside the cocoon. Upon hatching, the wasp larva consumes the bee and completes its development inside the cocoon undetected. The wasps emerge as adults from the cocoons by chewing a small hole in the side. These wasps develop very fast, so multiple generations can develop each season.

Control: use of solid nesting materials free of entry points, especially at the back of the nest. Nesting materials without backs or that are too thin are easily penetrated by Chalcid wasps.

Control: They are most active towards the end of the mason bee season. Therefore, completed nests should also be removed from the field and stored in a BeeGuard Bag or another breathable mesh bag at the end of the nesting season.

  Sapygid Wasp

Type of Parasite: Theft

Several different sapygid species are associated with solitary bees, so their appearance will vary, but adults are typically black and yellow and measure up to about 1/2 inch long (12.7 millimeters).

Sapygid wasps are cleptoparasites of both mason and leafcutter bees. The female oviposits her eggs into the nests of solitary bees, and the developing wasp larvae consume both the developing bee and the pollen loaf. These wasps then spin cocoons and overwinter undetected as adults alongside neighboring bees. Watch for Sapygid wasps in the summer! Sapygid wasps lay their eggs in the nests of bees while the female bee is away foraging.

Several different sapygid species are associated with solitary bees, so their appearance will vary, but adults are typically black and yellow and measure up to about 1/2 inch long (12.7 millimeters).

Control: Watch for Sapygid wasps in the spring and summer! Sapygid wasps lay their eggs in the nests of bees while the female bee is away foraging. If you find this parasitic wasp hovering near your bee house, spray it with a fine mist of water to stun and then kill it.

  Chrysidid Wasp

Type of Parasite: Cleptoparasite

About 1⁄2 inch in length (12.7 millimeters) and are typically metallic green in color.

Multiple species of Chrysidid wasps also prey upon mason and leafcutter bees. These native wasps are not as destructive as Chalcid wasps. Female wasps lay their eggs in nesting cavities while female bees are out foraging. Once the eggs hatch, the wasp larva attaches itself to the bee larva, which it begins to consume. After feeding, the wasp larva then spins a thin, semi-transparent cocoon and overwinters as adults. Unlike Chalcid wasps, Chrysidid wasps only produce one generation per year.

Control: These are minor native predators and often don't require control.