WINGLESS FRUIT FLIES FOR BETTA FOOD How to raise and collect them.

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If you've looked over my main page, you will know that I'm no stranger to growing fruit flies. I cultured thousands of them for research on hummingbirds but I had never thought of using them as betta food until one visitor to my site mentioned that she regularly used a wingless species for that purpose. Intrigued, I ordered a starter culture and some food from The Bug Farm.

The flies arrived in a 1-inch diameter, three-inch long vial capped with a porous plug. There looked to be twenty, small golden-brown flies actively crawling around inside the vial. The fly food came in a pint plastic bag and looked like instant mashed potato flakes. I believe that is what it is with some sugar added. The instructions say to add a pinch of yeast to 1/4-cup of the dry food, mix in 1/4-cup of water, and stir. The mixture turns blue-green and sets up to the consistency of somewhat dry mashed potatoes. On 21 March I placed this mixture in the bottom of a 20-ounce plastic water bottle, shook the flies into it, and capped it with mosquito netting held in place with a rubber band.

The flies showed no interest in climbing up the sides of the bottle even though they could easily do so. Instead they seem happy crawling all over the pile of food on the bottom. I suspect the requirement of capping the bottle is not so much to keep them in as to prevent wild fruit flies from finding the bottle and contaminating the culture. It should take at least a week before anything happens.

Four days after adding the fruit flies to my culturing bottle I could see baby-fruit-flies-to-be (maggots) burrowing though the growing medium. Their bodies were such a perfect match to the color of the medium that they were almost impossible to see but they have a dark nose they move back and forth to push their way through the medium. This movement is easy to spot. I transferred the adult flies to another container to start a second culture.

On the seventh day of the first culture, 150 maggots climbed the sides of the container and formed hard chrysalises around themselves. These should hatch into adult fruit flies in three more days.

Scary Math: It occurred to me that from 20 fruit flies I got 150 fruit flies. Now if I culture the 150 flies I'll get 1125 flies, and from that 8438, and from that 63,281 flies, then 474,609, and after the sixth generation, which would only have taken 84 days, 3,559,570 fruit flies! That would allow me to fulfill every American's dream: to become a millionaire! Of course, I suppose dollars would be better but we can't have everything.

On 30 March, the pupa in the vial in which the flies arrived crawled out of their shells as adult flies. From the shipping date, I estimate it took 15 days for eggs laid on the first day the flies were placed in the shipping container to when the first of the next generation appeared. That would suggest that the culture I started on 21 March will be up and crawling around on April 4 or 5. Because the flies were in this second culture jar for 5 days, eggs were being laid, hatching, growing, and flies should be coming into maturity over a similar length of time. Since that culture, I've been starting new cultures each day using the original flies. It'll be interesting to see if it's easier to start small cultures every day, or have fewer larger cultures that produce flies over a week or so. I should have the answer to this question, as well as how well the bettas take to eating the flies, by the update planned for 14 April.

By the way, It's easy to tell which pupa are about to hatch. They start out beige and turn darker as they mature. When they get almost black, they're ready to hatch.

The first culture I started on 21 March had 40 new fruit flies in it on 1 April. That suggests an egg-to-adult cycle of only 11 days, 3 faster than what The Bug Farm said it should be. This culture was inoculated with the purchased fruit fly culture for 4 days during which the flies continuously laid eggs. It's therefore understandable that maggots should be maturing over an extended period of time. Even while the first flies are crawling out of their pupating shells, mature maggots are still crawling up the sides of the container. This indicates that a culture inoculated for several days will produce flies for up to one week. This seems to be an easier way to grow them than starting a new culture bottle every day.

Of course the important question is: Will the bettas eat the flies? The answer is YES! I gave some to ten bettas and all but two immediately attacked the flies. An interesting thing about the flies that weren't eaten by these two finicky bettas was that they did not escape or hide in a corner of the jars. Rather, they clustered together like a floating island in the center of the jars.

Although I've only just started culturing wingless fruit flies, my impression is that they are cheaper, easier, and cleaner to raise and feed to bettas than it is to purchase and maintain brine shrimp.

 

 
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