Pests & Diseases

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European Wasp

Biology and Control

Pest Status

European wasp (Vespula germanica, family Vespidae, order Hymenoptera) has an unbarbed sting that can be used as a weapon with lethal potential (anaphylaxis) to humans and animals.  Generally wasps are a public nuisance and a horticultural pest (eg pest to grapes and staff in vineyards and wineries) in Australia.

Biology

The entire life cycle of the wasp lasts 3–4 weeks and the wasp colony generally lasts for one season (approx 6 months).

Immature Stages

  • Oviposition - egg laid, coated with secretion and pressed onto wall, generally angled towards centre of the comb
  • Embryology - egg consists of outer chorion, yolk and fertilised cell. Embryo differentiates and elongates until larval emergence

Dorsal view of egg

Dorsal view of egg

 

egg at 13 segment stage

Egg at 13 segment stage

 

The larval stages

  • The new larva emerges by rupturing the egg wall (eclosion) - 5 days up to 8 days
  • Larva grows through a series of stages or 'instars'
  • At the end of each stage a new skin is formed inside and it wriggles out of the old skin (ecdysis)
  • There are 5 larval stages
  • The first 3 stages face outward (5–8 days), the last 2 face inward (5–16 days) stage 4 leaves the egg shell and can move around the cell using the pleural lobes, the mandibles are maturing, ? can also see the spiracles, 9–22 days

The cocoon

  • The cocoon is spun with salivary gland secretions; capping first, then the rest of the cocoon. The larva rotates once to do this.

The pharate pupa

  • Can see the thorax through the larval skin, (3 days) larval–pupal ecdysis follows

The pupa (exarate)

  • Antennae, legs and wings free from the body, pigment develops gradually (3 days).

Pupa

The adult

  • Pupal skin becomes transparent and is peeled back to the base of the cell. Adult rests (2–3 days). Eventually bites its way out of the cocoon.

At the emergence of the first workers 3–4 weeks after oviposition started, the queen stays in the nest and lays eggs.

Life history

  • The foundress queens in spring, find a nest site, and begin the construction of a paper nest.
  • The queen rears workers for the first few generations. The new workers stay in the nest for 3 days - then forage after an orientation flight.
  • After 5–6 weeks the queen can relinquish her foraging duties, and over time she fades and frays.
  • Workers live up to 3 weeks.
  • The nest enlarges and then levels off. At the end of the season daughter queen cells are initiated and males are produced. Males have capped cells that are flush - queens have caps that protrude.
  • Nest decline - the founder queen dies, the remaining workers lay eggs, but these rarely reach maturity.
  • Foraging decreases, the nest temperature drops forcing the workers to leave and the last wasps die of old age. Males last the longest but the hibernating queens are all that’s left.
  • The old nest succumbs to degradation from insects and fungus.
  • Overwintering nests - occurs in the southern hemisphere. Most probably 'requeening' takes place before the old queen dies. Males, females and workers are produced in low numbers over winter. In the next season, the proportions of wasps shifts to mainly workers.

Complete life cycle

 

Identification

  • The black and yellow coloration is the most striking characteristic of these wasps.
  • The distinguishing feature between European wasps and bees is that the wasps have yellow legs.
  • Generally the nest is underground, but can be found above ground (eg in house eaves) or in vegetation (eg in palm tree trunks).

 A pictorial guide to wasp identification

Control

Direct

  • Locate the nest and destroy with insecticide (done by licensed operators within council or private contractors).
  • Traps (commercial or home-made) may alleviate problems with small localised populations.

Indirect

  • Environmental management; reduce opportunities for wasps to forage on rubbish, pet food, and other food sources and where possible minimise access to water.
  • Exclusion of wasps from residences and factories by screening openings.

More information

If you would like to know more about European wasps there is information and images on the following topics available on the following websites: