Tag Archives: larva

Neighborhood Mosquito Watch

During a run this week I passed an abandoned, 30-gallon aquarium with easily 10,000 larvae doing their thing (wriggling). I came back later, took some photographs (on my Instagram soon if you’re into that), and then dumped it, sending the larvae to their deaths but also releasing a cloud of perhaps 100 newly-eclosed adults. I suspect the aquarium had been there for years, pumping Asian tiger mosquitoes (Aedes albopictus) into the neighborhood. Given the aquarium’s location at the edge of busy parking lot I’m sure that thousands of people have looked at it and thought, “Huh. Looks like an abandoned aquarium full of dirty water. Next to a Christmas tree. I bet there’s a story there!”, and then moved on with their lives.

Abandoned aquarium with mosquitoes

In case you are unsure what an infestation looks like, the next two photographs show what the adults, larvae, and eggs look like. Asian tiger mosquitoes lay eggs singly on the sides of containers or on moist objects floating on the water. They can last over a year as an egg, waiting for conditions to be just right.

Male Asian tiger mosquito (Aedes albopictus) with larvae

Female Asian tiger mosquito (Aedes albopictus) with larvae and eggs

Here’s a sample of the water I pulled from the tank.

But not all the eggs were Aedes albopictus (there are 60 species in PA alone). Here’s a raft of eggs in the aquarium from a different species (Culex sp.). The raft is lodged on a leaf but normally it just floats around until the larvae pop out. Anopheles (another common genus) has eggs that are deposited singly but float with the help of cute little life preservers.

Raft of mosquito eggs

But that’s not all! Yesterday I found a recycling bin behind a church with similar numbers of larvae. Given the amount of leaves decomposing in the bottom I suspect it has been like this for at least the whole summer. Again, it really is strange that nobody did anything about it. It’s right next to a sidewalk that gets lots of traffic (at least on Sundays) and is probably 10′ away from a playground at an infant/toddler daycare center. Poor kids. (I dumped it.)

Recycling bin with stagnant water

Given how much people hate mosquitoes it left me thinking how the public outreach about mosquito control has failed on the most basic level. Everyone should know enough about mosquito biology to know how and where they breed, and everyone should feel empowered to do something. Being proactive is so much better than adopting what I think is the common view, “Well if the mosquitoes get bad enough I’m sure the government will spray insecticides from planes.

All it would take would be a nicely worded message from a town official to mobilize residents into a mosquito watch. Something like, “If you see mosquito larvae swimming around in a container when you are out walking your dog, please turn the container upside down or alert the owner about it. Thanks.”

Pyractomena borealis mouthparts

Here are several anterior close-ups Pyractomena borealis. The telescoping head allows the larva to inject (via curved, hollow mandibles) a numbing agent into snails that have retreated inside their shells. The antennae and maxillae are also partially retractable. When a larva is done feeding on a snail (or slug or earthworm) it will de-slime all of these parts with the hooked, fingerlike projections of the holdfast organ (pygopod) located on the last abdominal segment. The head is also fully retractible (see previous post). These larvae are extremely active, so really hard to photograph.

Pyractomena borealis

Pyractomena borealis (Lampyridae) exploring the surface of trees on a warm winter day in February. At first I thought it might be foraging — they are highly predaceous, and hunt slugs and earthworms (in packs!) by first injecting them with paralytics. But it turns out they are just looking for a place to pupate.

Here is a close-up of the fully retractable head. Those mandibles are hollow.

Pyractomena borealis mouthparts

Here’s a photograph showing a retracted head.

Adults of this species will emerge from pupae sometime in early Spring to be the first fireflies in the area.

The larvae are bioluminescent, too, by the way. The hypothesis about why the larvae glow is that it evolved first as an aposematic trait in larvae, warning mice and toads of the presence of lucibufagins, steroidal toxins in the hemolymph. It’s thought that the adult habit of using flashes is secondarily evolved, millions of years after the larvae evolved the ability to glow. The ability of larvae to glow even predates the origin of the Lampyridae, I gather. For more enlightening details, see Branham and Wezel (2003)Stanger-Hall et al. (2007), and Martin et al. 2017.