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 Best way to hold larvae over the winter? 
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Joined: Fri Apr 26, 2013 4:40 pm
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Location: Olympia, WA
Post Best way to hold larvae over the winter?
We have about 3-4 months of warmish weather here in the PNW. I can't depend on native BSF.

I currently have a nice batch of acquired larvae growing in a small tote.

Now, supposing that I can get them to turn into flies, and the flies breed and lay eggs, I could have a second batch growing as fall approaches. I don't want to lose them.

Do the experts here have any advice on how best to carry them through the winter? I know cool temps and reduced food will slow down their metamorphosis. But I could REALLY use some detailed ideas.

Winter here is mostly rain and cold with some snow, temps range from a normal low of 26ºF, 'warm' of ~40ºF, extreme lows of about 5ºF. The back of my home is not heated, so the room there is probably a more-or-less steady 50ºF or so. I need to check on that.

Any tips, ideas or information would be greatly appreciated.

Sue


Mon Jul 15, 2013 3:00 pm
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Post Re: Best way to hold larvae over the winter?
I remember reading on one of the reptile forums that the larvae will emerge as flies when kept in refrigerators. So I guess the temperature would have to be lower than that to keep the larvae from maturing.

I don't recall seeing any scientific papers with detailed data about how they overwinter.

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Mon Jul 15, 2013 3:08 pm
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Post Re: Best way to hold larvae over the winter?
Sorry Sue, I have almost no experience with overwintering larvae. I did once maintain a colony of juveniles outdoors in a BioPod, but it wasn't a scientific effort. On very cold days I covered the pod with a garbage bag and put a 100 watt light under it. By spring I still had larvae in the juvenile stage that were about 5 months old. A few had matured and pupated during the winter but the vast majority waited for spring. I wonder if it's better to overwinter juveniles?

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Tue Jul 16, 2013 10:15 am
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Post Re: Best way to hold larvae over the winter?
At the moment, I'm using this heater inside a 25 gallon utility bin, with the grubs in a smaller tote.
The bin gets covered with an old sleeping bag. This raises the temps from 60° F to 70° F, and the grubs are thriving.


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Tue Jul 16, 2013 11:26 am
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Post Re: Best way to hold larvae over the winter?
You might be able to employ something like I use for my winter time BSF egg incubation bin. I use an infrared reptile heater lamp bulb mounted to a socket inside a LARGE plastic cooler. The heater bulb circuit goes into a standard 115 volt outlet, but is interrupted by a 12 volt automobile relay that I have wired on a separate circuit running to a small automobile battery charger and cheapo household thermostat which interrupts the main circuit. When the temp inside the cooler drops below the thermostat set point (usually 90F), the thermostat kicks on and the relay closes thus opening the circuit to the heat bulb which then kicks on and rapidly warms the interior of the cooler. A few degrees over the set point, the thermostat clicks off, the relay opens, and the heat lamp shuts off. I also wired a small red diode in parallel to the 12 volt circuit mounted to the lid of the cooler so I can look out the window to assure myself the system is cycling on and off reliably. I also drilled a small hole in the cooler lid and stuck the probe from a battery powered digital meat thermometer down the hole. This allows me to check the internal temp without opening the lid.

(Yes, I am a mad scientist!)


Wed Jul 17, 2013 12:03 am
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Post Re: Best way to hold larvae over the winter?
"Yes, I am a mad scientist!"

That's fine with me! Mad scientists add spice to life.

My main problem is not keeping them warm as much as keeping them cool enough not to hatch out. Any idea on the temp range that might be most useful to me?

Sue


Wed Jul 17, 2013 2:08 am
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Post Re: Best way to hold larvae over the winter?
Sue there's a bit of data on this page (link) Bio-Conversion of Putrescent Waste by ESR International. Scroll down to the What Happens in Winter section.

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Wed Jul 17, 2013 10:00 am
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Post Re: Best way to hold larvae over the winter?
The problem with Dr. O's articles is that in some of them he isn't clear if he's indicating °C or °F temps. In your link he says "... as the temperature drops below 21 degrees, their ability to digest waste progressively grinds to a halt, and if they should freeze, they die." But the chart shows Fahrenheit.

If his 21 degrees is C, that's 69.8°F. Another source says that larval food consumption stops at 59°F.

In the same paragraph, he says "This tropical fly larva needs to be sustained at temperatures above 30 degrees if it is to continue to digest putrescent waste...". 30°C is 86°F. The temp for continued life, and the temp for digesting food are two different things. Other info indicates that larval food consumption stops at 59ºF, and says that 50–60°F is the temp range where the longest larval shelf life is achieved.

Another source says that "... larvae activity and growth slows below 77ºF (seldom pupating) and become inactive at less than 50ºF. They can withstand freezing temps (32ºF) for up to 4 hours before they die. Insects developing on high-quality feed seem to require fewer degree-days to develop than those on lower quality resources."

So, do you see why I'm confused? I want to separate the temp requirements between larval existence and larval usefulness for digesting waste. The two conditions are not one and the same. If the temp is suitable for food digestion, it is getting perilously close to also being suitable for pupating or hatching into adults, isn't it?

So, if they will freeze at prolonged temps of 32°F, and 50-60°F is the limit for pupating, would a temp range of 40-50°F be suitable for holding them for 6-8 months over the winter?

Would it be the same if they pupated, and would they hold over winter?

Sue


Thu Jul 18, 2013 6:53 pm
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Post Re: Best way to hold larvae over the winter?
BelgianPup wrote:

So, if they will freeze at prolonged temps of 32°F, and 50-60°F is the limit for pupating, would a temp range of 40-50°F be suitable for holding them for 6-8 months over the winter?

Would it be the same if they pupated, and would they hold over winter?

Sue


Judging from my experience when our average daily temp (day time high +night time low)/2 = 60F or less, yes, and yes! ;)


Thu Jul 18, 2013 9:54 pm
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Post Re: Best way to hold larvae over the winter?
Okay, now I've got some limits!

Thanks, Tarvus! The grubbies are growing, but more slowly than yours, I'm sure. When I check them in the morning, they're barely moving. So I move their tote into the sun and check them periodically. When they warm up, they get much more active, and then slow down again late in the day. Our days struggle to get up to 80°F, nights drop down to 50-60. Some have turned a bit beige, others are still white. I'm sure if they were warm all the time, they would mature faster.

Sue


Sat Jul 20, 2013 3:02 am
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Post Re: Best way to hold larvae over the winter?
A recent video by Northwest Redworms where he's experimenting with overwinter ing larvae in upright barrels using lights as a heat source.



There's more discussion about overwintering in this topic (link).

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Mon Dec 15, 2014 6:38 pm
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Post Re: Best way to hold larvae over the winter?
Since I haven't posted in over a year, you've probably assumed that the overwintering in W. WA either worked or didn't. It didn't.

I kept them in a plastic box in the cool unused bathroom in barely-damp sawdust. I would check them periodically, but being so cool, I could hardly see them move when I stared at them. I put them out in the greenhouse after the last frost date, but they had all croaked.

Too moist? Too dry? Sawdust was wrong? Color of the bathroom walls was wrong? Stars were in the wrong place?

I don't know. I've given up for now. That's four years running without success. They may know how to survive on their own, but I sure can't do it.

Sue


Mon Dec 15, 2014 9:00 pm
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Post Re: Best way to hold larvae over the winter?
Sorry to hear that Sue. Can't fault you for not trying and I wish the results were different.

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Mon Dec 15, 2014 9:10 pm
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Joined: Sun Aug 24, 2014 7:41 pm
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Post Re: Best way to hold larvae over the winter?
At White Oak Pasture, Bluffton, GA, we are rearing the larvae outdoors, not just overwinter, they are growing to full size in 7 days. No heating units are required.


Fri Jan 09, 2015 10:21 am
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Post Re: Best way to hold larvae over the winter?
That's great Alfredo. I look forward to specifics.

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Fri Jan 09, 2015 12:27 pm
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Post Re: Best way to hold larvae over the winter?
Here in Central FL, I am running a two "dry" bins inside a cheap plastic greenhouse. I am still seeing active growth and feeding in both bins with plenty of adults still emerging (not sure about mating activity). I think the key to the ongoing success of the bin is that it is dry and I am liberal with coffee grounds which tend to heat up well as they decompose. I have a small bokashi bin i put all my food and coffee waste in and when it is full, I shovel it into the bins.


Tue Jan 27, 2015 12:06 am
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Post Re: Best way to hold larvae over the winter?
MRW any chance you could post some temperatures? It would interesting to know the bin vs the air temperature.

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Tue Jan 27, 2015 1:13 am
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Post Re: Best way to hold larvae over the winter?
I don't really have a thermometer I can use, but I will tell you that the zippers are shot on the green house, so i only gets really warm in there when the wind is not blowing. really, it is just slightly above ambient which this time of year ranges from 50-70. I think on the warm days I might get some mating - maybe just enough to keep the colonies going. The frass/worm mix feels cool in the mornings and warmer later in the day.


Tue Jan 27, 2015 11:58 am
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Post Re: Best way to hold larvae over the winter?
I'm in Northern California. Temperature range has been 65-40F. Last Summer was my first experiment with BSFL. By the end of the season I had two 32 gallons bins of active larvae, fed entirely with quail poop. They've been dormant over the winter obviously, and I stopped feeding them since November. Recently I dug up the manure and found that there're plenty of tiny little white larvae, about the size of newly hatched larvae. They wiggled VERY slowly. I'm happy that they are alive! Hopefully I won't have to purchase new seeds this year.

When can I start feeding them again? The quail manure substrate is pretty thick right now, probably hard to larvae to wiggle through to the top to get new food. Do you think it might help to fill the bins with water to loosen it up and drain the water, before feeding them again?

I'm thinking of building a "boat" this year. My ramps weren't sufficient for them to climb out last year, and I do have A LOT of quail poop to process.


Wed Jan 28, 2015 5:16 am
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Post Re: Best way to hold larvae over the winter?
CookiesDaddy wrote:
... When can I start feeding them again? The quail manure substrate is pretty thick right now, probably hard to larvae to wiggle through to the top to get new food. Do you think it might help to fill the bins with water to loosen it up and drain the water, before feeding them again?
I would wait until it warms up although there is a school of thought that if fed they'll use the energy to warm themselves but not grow. See the link in this post (link) further up is this thread.

As for adding water, how wet is the bin now? More water might conduct any heat to the outside lowering the temperature in the bin and killing the larvae.

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Wed Jan 28, 2015 1:09 pm
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