Bloodworms (Chironomid larvae). Too bad about the "worm" part of the name. I'd like to call them "blood larvae," but then no one would know what I meant. Bloodworms aren't worms at all, but a collective term for a great variety of aquatic larvae of many similar non-biting midges related to the species Chironomus (hence "Chironomids"). The term "bloodworms" is made unnecessarily confusing because some people miscall tubifex by the same name, but in fact the red coloring of these larvae does indeed come from the oxygen-carrying pigment, hemoglobin, that makes our own red-blooded blood blood-red. Not all the larvae of Chironomids are provided with hemoglobin, but the ones that have this advantage are able to get by on much lower levels of dissolved oxygen.

Chironomid midges are among the non-biting ones that swarm on summer evenings. The eggs are laid in the summer and autumn and overwinter as larvae in the bottom mud; that's why they're only seasonally available, like glass larvae. When they are available they can even be collected in large enough numbers to be freeze-dried and marketed. And lately live bloodworms turn up in those breathable sachets on the counter of your high-end LFS. Ounce for ounce, do they cost as much as caviar? Could be.

At certain seasons chironomids can be alarmingly numerous. I'm reading (in a post on bio.net, Jan 1996) that Chironomid midge larvae are often the most abundant macroinvertebrates, both in the number of individuals and in the numbers of species, in many tropical freshwater systems. They have evolved into a great number of species. Singapore's small tropical island registered over fifty species before urbanization transformed it. There are lots of unknown species in the Neotropics that are waiting to be studied and formally named and published. So if you're wondering what are the most natural livefoods for your fish, Chironomids offer a set of candidates.

Sub-fossil chironomids in lake sediments help paleontologists date the layers and help characterize paleoclimates. Naturally a whole Chironomid scientific industry has developed. All the serious midge-heads hang out at The Chironomid Home Page.

Adrian Tappin has more introductory material on Chironomids at "Home of the Rainbowfish" .

Culture? In spite of the difficulty of getting the adult midges to mate in captivity, fish breeders in Hong Kong and Singapore have been sucessfully culturing bloodworms during the last couple of decades. Dependable culturing techniques to serve Singapore's huge aquarium fish farming industry needed to be worked out, as Singapore's urbanization has destroyed many natural collection points for bloodworms. The University of Singapore had an informative illustrated article on chironomid biology and culturing that was at the sometimes-impenetrable National University of Singapore website. If you're interested, I suggest you run a search for "chironomid culture" through an engine like www.google.com.

Bloodworm terrors. Midge larvae are sometimes parasitized by a hair-thin white worm, all coiled tight within its cercaria, lodged in the larva and up to 2 inches long. When a fish crushes the Chironomid larva in its mouth the encapsulated worm is sometimes set free, and creeps out the gill opening: ee-Yow! ...making the appalled fishkeeper pass out cold from sheer anxiety. Fear not! This is Gordius, a parasite of insects. Usually it just gets chewed up. It does not bore through the intestinal wall like the alien in Alien I. It does not even parasitize fish at all. It will live free in the water for months in the aquarium, eating nothing and laying microscopic eggs, in the vain hope that some passing midge will select your aquarium to develop its larval brood, and one of them will ingest a Gordius egg. Fat chance, eh!

Some people are seriously allergic to bloodworms, and their hyper-sensitivity increases with each exposure. Wash your hands thoroughly after feeding bloodworms, even the freeze-dried ones, which I handle with tweezers. Don't rub your itching eyes til you've washed your hands, and be on guard for any tell-tale rash, tingling or shortness of breath. If you experience troubling symptoms, leave off the bloodworms.