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Aquatic Flies

Last Updated: 11/1/13

Black Flies
Crane Flies
Dixa Midges
Drone Flies
Horse Flies
Phantom Crane Flies
Phantom Gnats
Sand Flies
Soldier Flies
True Midges - bloodworms, leaf-mining midges

Mosquitoes - including mosquito control - on their own page!

Diptera is a huge order. Many larvae and pupae are aquatic. No adults live in the water. Most fly larvae lack eyes, and it is hard to tell which end is the head. They are a major food for fish and other animals in ponds. Here are some of the species or groups of species most frequently encountered.


Black Flies

Here are some blackfly larvae on a waterfall that Stuart sent to me on 10/7/04. More on this below.

Black flies (Simulium species), or Buffalo Gnats, can be identified by their large, bulbous rear ends as larvae. They prefer streams. Adult females bite to suck blood, and it hurts! Adult males drink nectar. Adults look similar to small bees. They are active during the day. Larvae have a bulbous rear (unlike midge larvae) and two brushes on their head to gather food. They attach themselves to rocks by their rear in moving water. Larvae eat small bacteria, diatoms, etc. There are about 50 North American species. Larvae and adults are both about 0.2 inches long and black. Some species can carry deadly waterfowl malaria that kills waterfowl and turkeys that are bitten by a black fly that has it.

Drawings of a larval and adult black fly can be seen at this site. This is an archived version as the site no longer exists.

On 10/7/04, Stuart sent me some photos of "worms" for identification. He was worried they might harm the koi or pond. They were blackfly larvae. While the adult females may bite humans, the larvae are of no threat. Fish love to eat them! For some reason, when removed from the water, the live blackfly larvae's tell-tale bulbous rear partially deflates. Here are three photos that he sent of blackfly larvae:
Blackfly larvae on the waterfall - same as above photo, kind of look like leeches if the rock were a "victim"
One blackfly larvae - close-up, head at the bottom
Four blackfly larvae - close-up

Karen sent these two photos on 9/1/07 of her stream with pond snails and insect larvae in the water flow. The insect larvae might be blackfly larvae or perhaps caddisflies.
Insect larvae
Insect larvae

Bill and Michelle sent one photo of blackfly larvae on 8/31/08. I accidently uploaded the photos a few times.
Blackfly larvae
Blackfly larvae - larger version of the last photo
Blackfly larvae - close-up of the last photo
Blackfly larvae - close-up, different view

On 3/28/13, KC sent these three photos of animals in a stream in Idaho for identification. The small black animals with bulbous rears attached to the stream bed and plants are blackfly larvae. There are also a lot of air bubbles which other people have often confused with eggs.
Blackfly larvae
Blackfly larvae
Blackfly larvae


Crane Flies

An adult cranefly on my house on 6/10/03 on the left and a cranefly larvae from my 153 gallon pond on 3/29/04 on the right.

If you find a large 1-3 inch, fat, worm-like beast with tentacles on one end, you have found a crane fly larvae! There are 30 species of crane flies with aquatic larvae. The adults look like giant mosquitoes but either do not eat or only eat nectar. Larvae have a disk at their tail with spiracles (tentacles) that they stick out of the water to breathe. Some eat animals and some plants. They live in plant and algae mats, muck, and debris on the bottom of ponds. Tipula trivittata is a common species. The adults and larvae are both about 1.5 inches long.

Pond animals - 1463 KB, mpg movie.
This shows two crane fly larvae (the worm-like animals), a medium-sized green frog tadpole, and a baby rosy red minnow (at the bottom near the end of the video). This video is from 3/29/07 when I was cleaning out my 153 gallon pond (see this page for details).

From the 153 gallon pond cleaning on 3/29/07:
Two crane flies and a green frog tadpole sitting in my little bucket after I found them.
Two crane flies, a green frog tadpole, and a baby rosy red minnow in the bucket. Video of them is mentioned above.
Two crane flies, a green frog tadpole, and a baby rosy red minnow in the bucket.

From the 153 gallon pond cleaning on 4/1/08:
Crane fly larvae in my hand.

From the 153 gallon pond cleaning on 3/14/12:
Crane fly larvae

Adult crane fly on 5/30/12; there is a spider at the top too.

Drawings of a larval and adult crane fly can be seen at this site. This is an archived version as the site no longer exists.


Dixa Midges

Dixa midges look like midges, only larvae are larger. Adults are 0.2 inches long while larvae are 0.4 inches long. They have "hairs" at both ends used to filter small food. When at rest, they are bent in a U shape. There are about 8 North American species.


Drone Flies

Drone fly larvae are also called rat-tailed maggots due to their long breathing tubes. Adults are also called hover flies. I discovered drone flies in my tiny pond in the Fall of 1997. This pond can be seen here. Drone fly larvae are readily identified by their long breathing tubes which look like a long string (1-2 inches) attached to their rear. They keep the tubes sticking out of the water to breathe. Their bodies look like land maggots (the kind that make many female humans scream). They are only found in shallow water without predators (fishless ponds). Drone fly larvae are thus usually in polluted (nutrient rich) waters. They writhed from plants to pond bottom and back in my pond. Unlike other flies, these flies do not sting, bite, or otherwise cause problems for humans. In fact, adults look like honeybees and pollinate flowers. My batch was in the pond from about late September to mid-November. They were hardy, surviving a number of shallow freezes. One species of drone fly is Eristalis tenax whose adult is 0.5 inches and larvae 1.5 inches.

Drawings of a larval and an adult drone fly can be seen at this water bug site under red-tailed maggot fly.

Drawings of a larval and adult drone fly (under rat-tailed maggots) can be seen at this site. This is an archived version as the site no longer exists.


Horse Flies

Horse flies and deer flies have adult females who give humans painful bites. In 1999, I got one bite that left a welt for a week. Their larvae are aquatic. Horse fly adults are about 0.9 inches long while deer fly adults are only 0.4 inches long. Both look like big house flies with large eyes. Larvae are about 1 inch long. They look like fat, highly segmented worms. Larvae eat worms, snails, and small animals. Adult females eat blood while males drink nectar. One species of horse fly is Tabanus atratus, and one species of deer fly is Chrysops callidus. The American horse fly is Tabanus americanus and grows to about an inch long. It has bright green eyes.

Drawings of a larval and an adult horse fly can be seen at this water bug site.


Phantom Crane Flies

Phantom crane flies look like crane flies but their larvae have a long tube on their rear to breathe through, are more slender, and a little smaller. They live in decaying plants and mud at the edge of ponds. There are six North American species. One is Ptychoptera rufocincta with an adult of 1 inch and a larvae of 1.3 inches.


Phantom Gnats

The phantom gnat larvae looks like a mosquito larvae but adult phantom gnats do not eat. The 0.5 inch, clear larvae dart around. They eat mosquito larvae and small animals. Thus, they would be welcome in most ponds.


Sand Flies

Sand flies (Culicoides) are also called punkies or no-see-ums. These are biting midges. The 0.3 inch larvae eat small animals, and fish eat them in return.


Soldier Flies

Some species of soldier flies (Stratiomyia) have aquatic larvae. Larvae are 1 to 2 inches long with tufts at both ends. They appear lifeless due to their thick skin. Adults are about 0.4 inches long.


True Midges

Adult true midges look like mosquitoes (0.2 inches). Larvae look like tiny worms but with a head, tiny "feet" near their head, a smooth body with indentations (rings around their bodies creating segments), and fuzzy stuff at their tails. Larvae can be red, yellow, green, or white. The red larvae are "bloodworms" that aquarists buy to feed their fish. The pupae of many species can swim. Some species eat animals, some plants, and some both. Some species have larvae who make homes, like caddisflies. Fish love to eat midge larvae. There are some 200 North American species according to one source but Dale e-mailed me to say that a 1990 source lists 1051 species!

Bloodworms:
My pond filter is absolutely loaded with bloodworms, a type of midge larvae. Most likely, your filter is full of them too! They do no harm to the filter. Midges can tolerate pollution more than other insect larvae. Any that get flushed out make great fish snacks. Bloodworms feed on detritus in low oxygen areas of the pond. They are red due to high levels of hemoglobin.

Leaf-Mining Midges:
The leaf-mining midge, Cricotopus ornatus makes trails all over lily pads. The vegetation at the trails dies, turns brown, and rots. The larvae can be found at the end of the trails and be removed. Adults look similar to mosquitoes. Mosquito dunks may be used to kill larvae in the pond.

Drawings of a larval and an adult midge can be seen at this water bug site.

Drawings of a larval and adult midge can be seen at this site. This is an archived version as the site no longer exists.


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