By Mariana Bulgarella & Phil Lester of Victoria University of Wellington, New Zealand
Sadly, this is yet another story about an invasive insect species negatively impacting the Galapagos Islands. The yellow paper wasp, Polistes versicolor, first reported in Galapagos in 1988, has now spread to almost all the islands of the archipelago. The control of P. versicolor is a high priority because of its increasing impact on biodiversity and the well-being of Galapagos residents and visitors to the islands.
Polistes has a powerful sting that can cause severe allergic reactions in humans (which is especially important when you are more than 1000 km from the closest mainland). Large wasp numbers are commonly found in human-inhabited areas such as visitor sites, vegetable markets, and farms. During El Niño years when climatic conditions are extreme, wasp numbers have been exceptionally high, seriously affecting human activities. Some Galapagos tour companies have abandoned specific visitor sites because of high wasp abundances, and some even include advice on their websites to pack light-colored clothing so as not to attract wasps.
A major concern is that of the impact of the paper wasp on Galapagos biodiversity, as they are voracious predators of invertebrates. In Galapagos, these wasps exert substantial predation pressure on native insects, which, in turn, has indirect consequences on community composition and ecosystem functioning. The invertebrates eaten each day by wasps are no longer available for other insectivorous species such as Darwin’s finches, geckos, and lava lizards.
We became involved in this project in 2017 to develop an effective control method for the invasive wasp. Our project is a collaboration among researchers and natural resource managers from the Charles Darwin Foundation, the Galapagos National Park Directorate, Escuela Superior Politécnica de Chimborazo in Ecuador, and Victoria University of Wellington in New Zealand (that’s us).
We started our work on Santa Cruz Island at the end of March 2018. Our goal is to find a highly attractive lure that traps and kills wasps in large numbers. The work is challenging, as no previous baiting system has been successfully developed for these wasps. But we are encouraged by the local knowledge and experiments involving the use of yellow pan traps and fermenting fruits in liquid. We are testing various chemicals associated with fermenting fruits — some of which do seem to attract the wasps.
In addition, with the help of the Charles Darwin Foundation research staff, we have captured and dissected wasps. We hope that some gland contents will prove attractive to wasps and thus potentially facilitate pheromone traps. Pheromones are chemicals that trigger a social response that might confuse the wasps and lure these stinging invaders to their death. Here in New Zealand, we are now conducting biochemical analysis to identify any pheromones from these dissected wasps that might prove useful for control.
We have similar problems with invasive paper wasps in New Zealand. Our goal over the next three years is to develop a control method that will benefit both the Galapagos Islands and New Zealand. We look forward to helping prevent this attack on native species, and to a day when visitors to Galapagos no longer complain about wasps. Unfortunately, wasp control won’t happen tomorrow, but it is our long-term goal!
Professor Phil Lester from the School of Biological Sciences at Victoria University of Wellington is an entomologist experienced in the development and delivery of social insect pest control programs in the Pacific. He is currently also leading a program to tackle wasp invasions in New Zealand.
Dr. Mariana Bulgarella is a Research Fellow in Phil’s research group working on invasive wasps. Mariana has previous experience with projects in Galapagos and South America studying population genetics, invasion biology, and bird-parasite interactions.