bald-faced hornet in Scrophularia auriculata flower

Dolichovespula maculata             Family: Vespidae
Common name: Bald-faced hornet

Host plant: various species

Adult size: 0.5 – 0.75 in (13 – 20 mm)

Beneficial predator


Life cycle:
           Generations per year: 5 – 7 depending on latitude
            Egg: 6 days
            Larva: 8 days
            Pupa: 9 – 10 days
            Adult: 122 – 170 days depending on latitude

 

Description & Life Cycle: The bald-faced hornet is not a hornet, but rather one of the many types of yellowjackets. They are black and white in colour versus the typical black and yellow of other yellowjackets which likely attributes to their being called a hornet. Notably, their face is white which explains the “bald face” in their name. Bald-faced hornets are larger than their yellowjacket counterparts.

Inseminated (fertilized) queens are the only ones to overwinter, emerging anywhere from the end of March in central California to mid-May in Washington State and southern British Columbia, Canada. The lower the latitude the longer the life cycle; the higher the latitude the shorter the lifecycle.

bald-faced hornet workersThe overwintered queen builds a nest out of wood cellulose she has gathered, chewed and mixed with her saliva to produce a paper-like material. Once a few brood cells have been formed inside the nest, she lays her first batch of eggs. The queen tends and feeds this first group of emerging larvae who will become workers and assume the chores of expanding the nest, collecting food, feeding the young larvae, and protecting the nest upon their maturity. (Photo right: 2 worker hornets: worker top left is building onto the nest; worker right is returning from a hunt to feed young larvae.)

Towards the end of summer, the queen will lay eggs destined to become future queens. She will also lay unfertilized eggs from which males, called drones, will emerge. Once mature, the new queens and males will leave the nest to mate. These queens will feed on nectar before searching out a suitable spot to overwinter in tree hollows, under bark, in rock walls, and even attics.

The new young queens are the only survivors. The rest of the colony, including the current queen, will perish when the first frost of winter hits.

 

Special Notes: Called a hornet, but not a hornet, this bee species is actually an “aerial yellowjacket”…one of about 8 species in the genus Dolichovespula. Exclusively native to North America, it is found in all Canadian provinces and territories, except Nunavit, as well as in all American states, with the exception of Hawaii.

This bee species is a social insect and lives in colonies of up to about 400 bees. Bald-faced hornets have a distinct caste system made up of:

  • Queens – fertile, egg-laying females; she is the largest in the colony
  • Workers – infertile females who continue nest building, tending young, collect food, and defend the colony from interlopers / invasion
  • Drones – fertile males (from unfertilized eggs) whose sole purpose is to mate with future queens; they do not have stingers

The grey, paper-like nests are typically large, pear-shaped structures tapering to a narrow entry point at the bottom. They can be up to 23 inches (58.5 cm) in length and 14 – 15 inches (35.5 – 38 cm) in diameter. They are usually built in trees and large shrubs but have been found near homes and other human structures which have flower gardens nearby.

Bald-faced hornets feed on nectar for quick energy but are wonderful hunters of insects which makes this bee a welcome beneficial insect to anyone’s garden…although they do not distinguish between good insect and pest insect when they are hunting.

 

large bald-faced hornets' nest In our Zone 7a garden: We have yet to see a nest colony in our garden, but did spot a large nest in a neighbour’s tree one block over from us. Wherever the bald-faced hornets make their annual home, we can always guarantee they will show up in our garden to hunt insects and feast on flower nectar, particularly from the Scrophularia auriculata ‘Variegata’ plants. These plants, commonly called variegated water figwort, are sited right at the entrance to what was once my herb garden…a point of entry which is much used in the course of a day spent working in the garden. Truthfully, we have brushed right up against the branches where many of these hornets have been feeding on nectar, and have yet to be stung. This gives credence to the claim bald-faced hornets are generally docile unless their nest is disturbed. In that case, it is best that you run. Fast.

Because of their docile nature, and the fact this bee does so much good work in the garden for us, assisting in keeping the pest insects under control, it is highly recommended you do not destroy their nests or kill the bees. Unless of course, they have built a nest in an unfavourable location on your house.

 

Posted on April 11, 2018