Watch out below: wasps battle ants by dropping them

ImageOne of the most successful invasive species is the common wasp, Vespula vulgaris. Dr Julien Grangier recently demonstrated how foragers of this wasp have adopted previously unknown interference behaviour when competing for food with native ants. Picking their opponents up in their mandibles, flying backward and dropping them some distance away from the disputed resource, wasps were shown to efficiently deal with a yet aggressive competitor. The wasps modulate this behaviour according to various circumstances including the abundance of ants. In this second paper we further discuss the nature and functioning of this unusual strategy. We first highlight the questions this interaction raises regarding the competitive advantages offered by asymmetries in body size and flight ability. Then, we argue that this study system illustrates the important role of behavioural plasticity in biological invasions: not only in the success of invaders but also in the ability of native species to coexist with these invaders.

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Our initial paper describing this behaviour was published in BIOLOGY LETTERS. Associated with this article was a video published in YouTube, which has been viewed over 60,000 times. We were invited to publish this paper in COMMUNICATIVE & INTEGRATIVE BIOLOGY in 2012. The work was covered in the journal Science and the National Geographic.

Nematodes in New Zealand native ants

Diploscapter formicidae sp. n. (Rhabditida: Diploscapteridae)

Ever dissected an ant and found it to be jam packed with will little worms? Evan Brenton-Rule, Julien Grangier  and Monica Gruber have. The article on nematode infections in native ants is out “on-line early” in Nematology. With a Landcare Research Ltd scientist (Dr Zeng Qi Zhao) they describe a new species of nematode commonly infecting the native ant Prolasius advenus. While females of this nematode were abundant, we have yet to find a male, which indicates males may be absent or rare in this species.

The full article can be found, with some amazing microscopy images, on line in the journal NEMATOLOGY.

Pesticide effectiveness for Argentine ants depending on hunger & differs for workers and queens

Argentine ant queen and workers

How effective are our current control methods for Argentine ants? Melissa Mathieson has just published an article suggesting varying efficacy for pesticides to New Zealand populations of this global invader. She showed that even the most effective pesticide, Xstinguish, was less effective in controlling queens in an ant nest compared to workers. Queen mortality in a nest ranged from nil to extremely low when the ants were starved for only 24 hours. The pesticides failed to kill all queens even when nests were completely starved for 48 hours. These results agree with our field observations. Commonly we’ve observed ants to survive or reappear very quickly after pesticide treatment. This reappearance may be from reinvasion or from the survival of treated colonies as this study suggests.

The full paper can be found here in the JOURNAL OF ECONOMIC ENTOMOLOGY. Or grab  a REPRINT here.

Yellow crazy ants spread but decline in densities on Tokelau

Monica Gruber

Monica’s paper on the invasion of Tokelau by invasive yellow crazy ants has been published “on-line early” in Biological Invasions. In it she decribes the continuing invasion of a new haplotype of these ants. But she also describes how population densities have changed and that local residents don’t consider this top-100 pest species to be so much of a problem as it used to be.

The link to the full article has been published online in the journal BIOLOGICAL INVASIONS. Or grab a REPRINT  here.