The Piñata of Peril (Paper Wasps)

June 2011

Are these normal paper wasps?

Answer

Incomplete nest showing comb and partitions An incomplete Ropalidia romandi nest The nest is now partly covered by an envelope The nest is now partly covered by an envelope Coverered and completed wasp nest A completed wasp nest

Commonly-encountered species of paper wasps have small nests with a few dozen or up to 100 or so wasps.  The species you have photographed, Ropalidia romandi, builds much larger nests. Your nest is 30–35 cm long, by comparison a 45 cm long nest held 19,000 wasps! These are aggressive wasps with powerful stings so keep a respectful distance.  And the largest nests of this species can be a metre long; one was estimated to have 130,000 cells, sheltering many tens of thousands of wasps.

In winter the nest is started by a swarm of a few hundred wasps including many queens. They select the underside of a gum tree branch or somewhere similar such as under the high eaves of a house.  The entire nest is built from a papier-mâché mix of saliva and fibres scraped from plants. Tough stalks to hold the combs are built first, to which the first storey of comb is attached. Additional stalks are attached to the first storey, and another level of comb is suspended beneath the first. Ten or more storeys are frequently built.  A cover or envelope is also built, usually while the combs are still being built. In these photos, in addition to the envelope, you can also see a regular arrangement of partitions flanking the combs. These will presumably support the outer envelope. When this nest is complete all you will see is the outer envelope with just one or a few entrance holes.  These nests are often not noticed when on a gumtree branch.

These nests are dangerous!  Do not try and knock them down. Contact a pest control operator if it is in an area when people could be affected. A nest is the life work and the next wasp generation, so the colony will defend their vital investment. The colony is alerted when large potential predators move too close. And it will be on very high alert if a wasp is damaged, or one has used its sting, due to release of a special alarm chemical.

Further reading

Fact Sheet: Paper wasps (299 KB) pdf document icon

Yamane,S. and Itô, Y. (1994), Nest architecture of the Australian paper wasp Ropalidia romandi cabeti, with a note on its developmental process (Hymenoptera: Vespidae). Psyche 101 (3-4), 145-158.

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