Mosquitoes – not just another splotch on the wall!

Posted by Hester Williams @HesterW123

I was lucky enough to attend the 66th Entomological Society of New Zealand Conference in Wellington a few weeks ago. I learned a lot about New Zealand’s insects and spiders and some very futuristic wasp control technologies. Along with this I met some really interesting characters (which is not surprising – entomologists are special people!)

Mosquito cartoon 1

The opening presentation of the conference was given by a very entertaining Ruud Kleinpaste: ‘Messages from Below: Bugs Biodiversity and Nature Literacy’. Ruud is very passionate about reconnecting our next generation to the Natural World and emphasised how we can use the environment as a context for education. He also encouraged us as entomologists to ‘tell stories’ to connect people with the environment. One thing that struck me was when Ruud mentioned mosquitoes and how our first reaction as humans is to ‘slap – good riddance!’, but he then followed to point out the role of mosquitoes in the Alaskan food web – mosquito larvae as food source to salmon, salmon as food to bears and birds of prey, etc., all with beautiful background photos.

To be brutally honest, mosquitoes have never been of much interest to me, except when out camping or when you hear that tell-tale whine in the dark. When I mention to people that I am an entomologist, a question that unvaryingly comes up is: ‘So, why are there mosquitoes?’. My general answer is usually that everything has a role either as food or as control mechanism in an ecosystem. But I decided for this blog I want to delve a bit deeper into the pesky mosquito’s life strategies to find their more unusual side.

The social isolation of the entomologist: 'Most people just want to talk about killing 'em.'

Interesting life history strategies

Mosquito females are well known for needing protein in the form of blood to produce eggs, but both females and males may also feed on nectar. Mosquitoes thus act as pollinators for grasses and a few other flowering plants, although they don’t actively gather pollen. Their role in spreading pollen hasn’t been studied nearly as much as their blood-sucking and disease-spreading habits. But the exception is their role in the pollination of bog orchids, including the blunt-leaved bog orchid, (Platanthera obtusata) that has been reported to be pollinated by several Aedes species, and other rare bog orchid species especially in the Arctic. Here, in the absence of an abundance of other pollinating insect species, the mosquito has heroically stepped forward to fill this important role.

Bog orchid

Figure 1. The blunt-leaved bog orchid, Platanthera obtusa, who depends on a mosquito species in the genus Aedes for pollination

During one of the teatime breaks at the Conference I had a chat with Dr. Mary McIntyre (University of Otago) and learned about one of New Zealand’s endemic mosquitoes, Maorigoeldia argyropus, an autogenous species which has largely or completely lost the blood-feeding habit. Reasons for the loss of the blood-feeding habit in many mosquito species are not yet understood but it is suggested that autogeny could be an evolutionary response to low availability of suitable hosts, and in such species the “burden of accruing materials for egg production is shifted from adult to larva”. Maorigoeldia argyropus has a limited and disjunct distribution in New Zealand, possibly as a consequence of extensive anthropogenic environmental change in the 20th century, and its long-term survival could be at risk.

Another interesting mosquito species is the pitcher plant mosquito, Wyeomyia smithii, which spends their egg, larval and pupal life in the water-filled pitchers (leaves) of the pitcher-plant (Sarracenia purpurea). The larvae feed by filtering particles arising from breakdown of prey (mostly arthropods) of the pitcher-plant. Interestingly the water temperature of pitchers in open sunlight ordinarily fluctuates from a low of 10-15 C to a high of 30-35 C in a single summer day, thus highly adaptable larvae! Similar to M. argyropus, W. smithii adults may feed on plant juices in nature, but on the basis of laboratory observations, they do not require such food to produce eggs.

Pitcher plant

Figure 2: Adult Wyeomyia smithii resting in a pitcher of the pitcher-plant Sarracenia purpurea (Copyright © 2016 tom murray)

The cattail mosquito (Coquillettidia perturbans), although a blood feeding mosquito, is also worth mentioning as far as interesting life histories is concerned. The larvae of this species has a specialized siphon to pierce the roots, stems, or submerged leaves of aquatic plants, enabling them to utilize oxygen from plant tissue and reducing the risk of being located near the surface of the water, as to avoid predators and insecticides. The adult stage of this mosquito was described in 1856, but because of its unusual behaviour the larva remained undescribed for more than 50 years.

While searching for interesting life histories and facts about mosquitoes I came across a lot of words like ‘annoying’, ‘vector’, ‘itchy’, ‘irritating’, ‘control’, ‘invasive’, ‘problem’, ‘dangerous’, etc., even a quote by the peace-loving Dalai Lama XIV: “If you think you are too small to make a difference, try sleeping with a mosquito.”

I have tried my best….slap….oops!

Hester Williams

Hester Williams is a PhD candidate in the School of Biological Sciences, University of Auckland and is stationed with the Landcare Research Biocontrol team in Lincoln, Canterbury. She is interested in invasion processes of both insect and plant species. Hester is supervised by Darren Ward (Landcare Research/University of Auckland) and Eckehard Brockerhoff (Scion), with Mandy Barron (Landcare Research) as advisor. Her studies are supported by a joint Ministry for Primary Industries – University of Auckland scholarship. The project is an integral part of an MBIE program “A Toolkit for the Urban Battlefield” led by Scion.

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