Thursday, August 30, 2012

A Beneficial Mosquito?

Toxorhynchites rutilus septentrionalis
Yes there is such a thing.  Mosquitos in the genus Toxorhynchites are carnivores in their larval stage, eating other mosquito larvae.  They get enough protein in the larval stage that they do not need a blood meal as an adult, so only sip nectar as a food source.

Jason Goetz, the Franklin County West Nile seasonal technician this summer, caught one while dipping in a tire a few weeks back and we've been rearing it out.

She emerged this morning.  Jenn Wetzel has been taking periodic pictures, offered here.

Toxorhynchites rutilus septentrionalis - larva
According to Mike Hutchinson, the Pennsylvania Department of Environmental Protection entomologist for the West Nile program:
One larva can eat up to 400 mosquito larvae during its development. Larvae engage in cannibalism as well as compulsive killing. Fourth instar larvae in an advanced stage of development stop feeding, but continue killing other larvae in the container, especially conspecifics [other members of the same species - ed.]. They have been observed grasping a larva and scraping it across needle-like spines on the posterior margin of the saddle, ripping the larva in half.
Yikes!  We did watch her eating a larva that we fed to her, but we did not observe that barbaric killing spree.

Toxorhynchites rutilus septentrionalis pupae
The most obvious difference about them is their size, easily 5 times the size of the average mosquito. 

Toxorhynchites rutilus septentrionalis
They have been tried as a biological control agent, especially in tire piles, but success depends on an expensive, and labor intensive rearing and release program, since their natural numbers would not sufficiently manage an outbreak.

Toxorhynchites rutilus septentrionalis
Maybe it's just parental pride, but I think she's just beautiful.

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