Wednesday, September 8, 2010

Wasp Wednesday: Northern Paper Wasp

When I lived in Cincinnati, Ohio I found the Northern Paper Wasp, Polistes fuscatus, to be among the most abundant of the social wasps. This has changed recently as the European Paper Wasp, Polistes dominula, has overtaken its native counterpart to become the dominant wasp, especially in urban areas. Still, most people living in the eastern United States and adjacent southern Canada are familiar with P. fuscatus.

Paper wasps belong to the same family as yellowjackets, true hornets, and potter and mason wasps: Vespidae. Whereas the yellowjackets tend to be wasps of northern North America, most diverse in boreal regions and cooler habitats, paper wasps are decidedly tropical, with only a handful of species ranging north into the U.S., and fewer still reaching Canada.

Paper wasp colonies are on the small side, rarely exceeding about 200 individual wasps. They build unprotected paper combs they suspend from twigs, stems, the eaves of homes, and other semi-protected locations. The stalk (pedicel) from which the nest hangs is sturdy and often coated with a dark substance that repels ants, the chief threat to the larvae and pupae inside the cells of the comb.

In North America, the life cycle of the nest begins when overwintering female wasps emerge from torpor and begin construction of nests. There is no apparent “worker” or “queen” caste in paper wasps, but recent studies have revealed that in fact some females are destined to become “gynes,” the reproductive females. Others will become subordinates to gynes. This is likely determined in their larval stage. More than one gyne may act as the “foundress” of a nest, but one individual eventually asserts her dominance, and the subordinate wasp leaves.

The gyne performs all roles as the nest founder, building the nest as well as securing food for her developing larval offspring. She makes the nest by harvesting fibers from wood surfaces, be it dead trees, dead woody stems, or fence posts. The fibers she scrapes she then chews into a saliva-soaked ball of pulp. Back at the nest she deftly plies the pulp into a strip of paper added to the existing comb.

Paper wasps are well worth having in the garden. They prey heavily on other insects, especially caterpillars. The Northern Paper Wasp has even been observed entering the silken tents of Fall Webworms to grab the hairy caterpillars. The wasp butchers her kill on the spot, stripping off any irritating hairs or spines that could not be easily consumed by the larvae back in the nest.

Once back at the nest, the wasp either feeds the larvae directly, or shares parts of the “meatball” with fellow workers that in turn distribute the food to the larvae. One larva occupies each hexagonal paper cell. Once the larva reaches maturity, it spins a silken dome over the top of the cell and then molts to the pupa stage. Shortly thereafter, an adult wasp chews its way out of the cap to freedom.

Late in summer, or in early autumn, the colony produces males. The male’s sole function is to fertilize the next generation of gynes. Watch a colony in August or September and see if you can tell the males from the females. It is actually pretty easy:

  • Males have long antennae, usually curled at the tips (females have shorter, straight antennae, though both genders have an “elbow” in each antenna)
  • Males have square, yellow faces (females have dark, triangular faces)
  • Males have a blunt tip to the abdomen (the abdomen of females tapers to a point)

Males and females both are abundant on flowers of goldenrods (Solidago) and throughworts (Eupatorium) at this time of year. With so many wasps easily visible at the same time, it becomes evident that the Northern Paper Wasp exhibits an extreme degree of variability in color and pattern. Most specimens will have a pair of large, deep red blotches on the second abdominal segment, but the yellow markings vary considerably.

Recent DNA analysis is adding mud to the situation instead of clarifying it, but chances are that the western “species” Polistes aurifer, shown below, is going to be lumped back in with Polistes fuscatus.

Enjoy watching these wasps. Their season is short, and unless you antagonize the ones on a nest (and they will give a threat display by standing on tip-toe and raising their wings), they make perfectly peaceful neighbors.

6 comments:

  1. I loved this post! I usually have paper wasps that build nests outside my upstairs windows, so I get to watch them the entire summer. I never knew that the yellow faced ones were male. I can't wait to tell the kids. I have one question. Of the females left at the end of the season, not all of them hibernate until the next spring? Only the gynes? Are more gynes produced during late summer, early autumn?

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  2. They have been keeping my cabbage worm away.I have seen them eating them on the spot.

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  3. About the P. dominula becoming dominant over P. fuscatus: at least here (Upper Peninsula of Michigan), the pendulum seems to have swung back the other way. About three years ago, we had P. dominula everywhere, and P. fuscatus was almost vanishingly rare in comparison. But after that, we had a particularly long and cold winter, and I haven't seen any P. dominula since then. The P. fuscatus have become quite common again, though: there are three active nests on the eaves of our house right now.

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  4. So even if you are the head gal wasp, you still have to do the same work as everybody else? A kinda more egalitarian community?

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  5. Great post, Eric! I was directed here by Bev Wigney, BTW. I lived around paper wasps for many years in NE Missouri but never made the detailed observations you have presented here. Thanks for your cogent and scientifically accurate summary of the insect's life-cycle!

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    Replies
    1. Thank you for the kind compliments!

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