Storm drains and mosquitoes
When is the last time you thought about a storm drain? Maybe when you read or watched Stephen King’s IT and saw a creepy clown sticking out of one?
Mosquitoes love laying their eggs in storm drains. The interior of a storm drain is often wet, full of leaf litter to eat, has cool air in the summer and warm air in the winter, and doesn’t have many predators. Some mosquito species have evolved to specifically make use of these artificial habitats, which is unfortunate as those same species can transmit pathogens like West Nile virus.
Look at how many mosquito larvae I found in just one storm drain in Triangle Cove.
The big ones that are easy to count are 3rd and 4th instar larvae, meaning they’ve grown and shed their skin 3 or 4 times. The small ones are 1st and 2nd instars, and are a lot harder to spot by naked eye. This one sample of water contains about 300 mosquitoes in 12 oz of water. The storm drain I took it from had maybe 2 gallons of water in it. 300 mosquitoes per 12 oz, 2 gallons of water per basin… that’s nearly 5,000 mosquito larvae in this one storm drain. You can look up how many storm drains are in your area thanks to Island County - here’s a link, check out the Catch Basin layer. Depending on where you live, you might have up to 20 storm drains around your street - that’s a whole lot of potential mosquitoes.
Hopefully that gives you a better idea of why I spend a lot of time inspecting and treating storm drains. Pictured above is a grate above a storm drain near Utsalady Elementary. Most people wouldn’t have spotted it through the leaf litter, which is why I keep a registry of storm drains and cross check it with Island County’s map. Sometimes they’re covered in leaves and hard to spot, but that won’t stop mosquitoes from finding and making use of them. The bag I’m holding in my hand is a water-soluble pouch that disintegrates after getting wet. Inside the pouch is a bacteria that is only harmful to mosquitoes called Bacillus sphaericus. Each pouch of insecticide will last about a month, at which point I’ll need to make another round to inspect and treat.
It’s good exercise and I haven’t spotted any evil clowns trying to pull me in yet, so I think I’ll keep doing it for the time being!