Drone fly larvae – “mousies”
Some time ago, Sandy mentioned to me that the bait shops sometimes sold something they called “mousies” for ice-fishing bait. After she described them, I suspected that they were actually drone fly maggots, but we wanted to confirm this. So, last January, we decided to get some and see what they really were. None of the local bait shops had any on hand at the time, so we ended up ordering some through the mail, which we received on January 12, 2013. They were mixed in with sawdust, mainly just to keep them from banging around in the tubes.
The dark ones had already started turning into pupae, but the pale-colored ones would crawl around dragging their long “tails”. You can get an idea of their size by comparing it to the tip of my finger that is also in the picture. My fingertip is about 3/4 inch wide.
At this point, I was pretty sure that these were, in fact, drone fly larvae (Eristalis tenax), because we used to have them around on our dairy farm when I was a kid. Any pocket of wet manure or manure runoff water that was allowed to stand for more than a couple of weeks would soon end up full of these, which we called “rat-tailed maggots”.
The “tail” is a breathing snorkel, allowing them to immerse themselves in the most noxious, festering masses of decomposing manure imaginable, while still being able to poke out the snorkel and breathe. Other flies specialized in the drier material, but these were right down there in the soup.
For final confirmation, I put some of the maggots into a jar with some water and some chicken manure, which they lived in for a couple of days before making their pupae. Putting them into the wet environment appeared to be important, as the ones that had already pupated in the dry shipping tube never came out, while the ones in the wet jar emerged on January 30, 2013.
The resemblance of the adults to honeybees is pretty good. It is easy enough to tell them apart once you are familiar with them, but to a casual observer the drone flies look an awful lot like honeybee drones.
There are a number of generally similar bee-mimic flies, but Eristalis tenax is the most common one. Particularly if there are manure piles around.
Not only do these flies look like bees, they behave a lot like bees, too. They travel from flower to flower, drinking nectar, and transporting pollen. Which means that they are important pollinators. They are also easy to raise. Which suggests to me that people who have crops that they want pollinated might have an alternative to paying to have beehives trucked in. Instead, they could place buckets of slop filled with drone fly larvae, timed to hatch out when the plant they want pollinated blooms.
Pollination with honeybees is a big business. They get hauled all over the country to pollinate various crops, particularly almonds in California. The problem is, these traveling pollinators also carry around every honeybee pest and disease in existence, and are partly responsible for the rapid spread of the Varroa mites that have made hobby beekeeping such a dicey proposition. Which is why I kind of think that an alternative pollinator, which shares no diseases with honeybees, might be a better choice for providing pollination services as it would make it possible for the honeybees to stay home.
At this point you might say, “Great! Let’s try this! Um, but how do you raise these flies in captivity, anyway?” Well, you could do it using this recipe from 1933:
The flies are kept in wire cages, 15x15x15 cm, containing watch glasses filled with cheese cloth moistened with tap water. In these cages are also small wooden feeding troughs filled with a mixture consisting of equal parts of dry poppy (Eschscholtzia californica) pollen and powdered cane sugar. On this food, the flies live perfectly and lay many fertile eggs.
The cages are kept before a laboratory window but are not exposed to the direct rays of the sun.
The eggs are collected and placed on human feces in a vessel also containing moist earth. Fresh feces are added daily. The larvae pupate in the soil.
At a temperature of between 20 and 25 degrees C, a typical female began laying eggs 10 days after emergence and laid about 3,000 eggs in about 60 days. The eggs hatch in about 36 hours after they are laid. The duration of the larval and pupal stages is about 2 weeks and 8 days, respectively, at about 22 degrees C. Oviposition has been observed at various temperatures between 20.5 and 30.5 degrees C.
The pollen can be purchased from the Knapp and Knapp Pollen Gardens, North Hollywood, California, or it can be raised. The poppy blossoms are collected each day. The anthers are clipped off with scissors and dried in the sun for 12 hours. The pollen separated from the dried anthers by means of a sieve with a fine mesh is kept in a dessicator over calcium chloride. Pollen rapidly deteriorates on exposure to moisture.
(reference: Dolley, W. L., Hassett, C. C., Bowen, W. B., and Phillies, G. (1933), “Culture of the Drone Fly, Eristalis Tenax”, Science, Vol. 78, no. 2023, pp. 313-314)
The pollen might be problematic, although there is a good chance that the pollen replacement sold by beekeeping suppliers might work just as well.