While walking around your ponds and streams, you may notice insect larvae swimming around. Insect larvae are an important part of our food chain, as many eat decaying vegetation and provide food for fish. While many of these larvae turn into benign, and even attractive insects such as dragonflies, others become biting flies such as mosquitoes. If you are interested in studying water larvae or avoiding the breeding grounds of biting flies, you should become familiar with the characteristics of common water larvae.
Identify the type of water where the larvae are found. Fresh running pond and stream water can house mayfly and some mosquito larvae, and slow moving ponds, marshes and streams can provide a home for dragonfly, damselfly, water strider, giant water bug, water scorpion, maggot and most mosquito larvae. Mosquito larvae are also commonly found in stagnant water that collects in buckets, birdbaths and pools.
Inspect the larva for identifying characteristics such as size, shape, length and special characteristics such as pincers. Mayfly nymphs, for example, are about 2.5cm long and have six legs with a claw on each end. Mosquito larvae look completely different -- they are segmented and tube-shaped, with tufts of hair coming out of each segment. Young water striders, who spend their whole lives in the water, appear like smaller versions of the adults, with four long legs skating over the water's surface.
Take a photo or draw a sketch of the larva if you need to look it up in a book or online later on.
Use an insect guide to compare your larvae to photos or illustrations in the guide. What's That Bug, listed in the references, is an online resource you can use to research aquatic insects and larvae. The National Wildlife Federation's Field Guide to Insects and Spiders of North America is another useful reference book which contains numerous colour photos of insects and larvae.