Regional differences in number of BSF generations per season

[BelgianPup]

I live near Olympia, WA, in a cooler "pocket", USDA 7b.  BSF are supposed to be found all the way up to Seattle, I've read.

Usually, we don't hit 70F until sometime in June.  While we may have warmer days, even in July and August daytime highs average only 77F.  Nights rarely get to 60F.

Since BSF seem to do their best at temps in the 80s, it seems like it would be an uphill battle for them to survive, or even naturally exist, here.

I've also read that in the south, there are three generations per year.  Why am I doubting that we would get that here? 

Also, all the info I've been reading talks about overwintering BSF in large enough numbers so they keep themselves warm with sufficient insulation.  But my question is how, with the temps we have, can someone build up a BSF colony large enough to keep itself warm for the winter?

Also, if I did manage to do that, would I be lucky to get one generation each summer?

If I'm overlooking something crucial, please point it out!

My 200 grubs are dark, but not moving much at 60F.

Sue

[Andrew]

"....all the info I've been reading talks about overwintering BSF in large enough numbers so they keep themselves warm with sufficient insulation."

Sue, I'm trying to overwinter a small (approx. 500-2,000 depending on how many eggs hatch & adults pupate) colony of juvenile BSFL and see what kind of temps they can maintain. Since the colony is small, I've put them in a small bin. I figured it'd be easier to insulate and the grubs would find it easier to huddle together for warmth.  I just set up the mini-bin today and will post updates.

If your 200 grubs are dark, they may be ready to pupate. If that's the case, they wouldn't be active even if your temps were higher.

As far as multiple generations, I think the critical factor is getting females to lay eggs in the bin. Whether it's the 1st or 3rd generation of the season, you just want a large number of juveniles to stall in their development at the proper season.

[GW]

Hi BP,

I have to admit that I'm not sure how BSF culture will be in your area. I'm so used to thinking of BSF in terms of tropical and subtropical temps that I was surprised to learn that there was a wild population of them in WA.

As Andrew points out you aren't simply limited by how many generations you might get in a year, you can still build up a large colony. Regardless of the number of generations you will still get continual mating and egg laying through the summer. In nature the vast majority of larvae would be eaten by other animals and by protecting them through their adult stage you can rapidly increase the size of your wild population. Don't worry, they won't become a nuisance and in fact you'll only see a few most likely.

In south Georgia I can build up a dense colony in about 4-6 weeks from the time mating begins. I'll bet that you'll be able to do the same in 8-10, maybe even less. Hopefully you can help us all find out next summer! 

[djeung]

I'm located just east of Seattle (Woodinville), WA and have the same concerns about overwintering as well as cultivating bsfl. To date, I've had difficulty getting the bsf to lay their eggs in the biopod. They have laid eggs in my compost bin. This will be the first winter of bsfl for me so I look forward to next spring to see how many survive. Question: If the bsfl have already turned dark and in the pre-pupae stage, will they survive the winter and hatch when the temperatures rise again?

[Andrew]

I've had difficulty getting the bsf to lay their eggs in the BioPod. They have laid eggs in my compost bin.

djeung, I had read your thread on populating the BioPod with interest. I figured I might have similar challenges to you here in the SF Bay area. I know BSF have laid eggs in my compost bin because I've found many of the empty shells left after the BSF have emerged from their pupa.

Although I'm hoping my small BSFL bin will survive the winter and build up enough scent to attract BSF females next Spring, I had also planned to rig some sort of egg laying platform (cardboard on sticks?) to place inside my compost bin. Of course I'd rather they lay the eggs directly in my BSFL bin, but I want to be prepared just in case they return to where previous generations have laid eggs. If any eggs are laid in the cardboard, I'd then transfer them to the dedicated BSFL bin to hatch.

This will be the first winter of bsfl for me so I look forward to next spring to see how many survive.

We're in the same boat! Have you insulated your BioPod yet? Come join us at in the cold weather thread:
http://thebiopod.com/forum/index.php?topic=145.0

If the bsfl have already turned dark and in the pre-pupae stage, will they survive the winter and hatch when the temperatures rise again?

This is what I assume will happen. I've moved the dark, mature grubs from the starter kit into a separate pupating bin that consists of mostly dry coir with just a corner of damp coir & a small piece of apple in case any of them are still eating. It doesn't look like they're eating (already exchanged mouth for a digger?) even though some are still moving around. I guess they're still looking for a nice spot to settle down? I had found one "unhatched" puparium in my compost heap and have been watching it to see if a BSF emerges. It's been 2 weeks since I found it and it's still dormant.

[GW]

I've had difficulty getting the bsf to lay their eggs in the BioPod™. They have laid eggs in my compost bin.

I've heard of this problem from a few people. I believe the issue is that the established compost pile is more attractive than the newer BioPod. I suggest manually transferring BSF from the compost pile using the method described here: http://blacksoldierflyblog.com/2008/07/25/collecting-immature-larvae/ I also suggest capturing eggs in corrugated cardboard strips placed above the compost pile as Andrew mentioned. The strips would be moved into the Biopod when eggs are found in the voids. Finally, if I had BSF grubs in the compost I would try to concentrate them with some fresh table scraps and then I would transfer a few gallons of the compost to the Biopod. Adding compost that contains some leaves and grass won't be an issue. The BSF won't eat those items but it won't disturb them in any way.

If the bsfl have already turned dark and in the pre-pupae stage, will they survive the winter and hatch when the temperatures rise again?

djeung, since wild BSF are present in your area we know they're surviving the winter in some form. In nature I doubt you would find a food source that would sustain them all winter so I imagine they're surviving in the form of pupae.

[BelgianPup]

I am trying to think ahead for this coming year...

Backing up a ways, I know that the instructions so far always advise keeping the BioPod in the shade.  But, as you have mentioned, you are used to most people raising BSF living in warmer parts of the U.S.  If I kept them in the shade here in W WA, I would have to knit sweaters for them.  I just can't believe that a small batch of grubs is going to overheat in a white 5-gal plastic bucket in the sun on most days!  I doubt that they would overheat in a BioPod, either.  (If I had large number of them, like masses (my goal), it would be different, of course.)

With our lack of warm temperatures in spring/summer/fall, I feel that I would be extremely lucky to get one new generation of grubs in the whole year.  I have been thinking how I could increase that number.

My theory:  once I get some more grubs in spring, I'll put them in a white 5-gal bucket with some food and put the bucket in the sun and monitor the interior temps with my 6" soil thermometer.  As long as it is under 95ºF, I'll figure everything is fine, and leave it in the sun.  Of course, if we get a heat wave, I will have to monitor the temps more closely and might have to move the bucket to the shade (*gasp!*).

I am hoping that I can keep the interior temps high enough for the grubs to grow faster so at least some of them can turn into adults in summer, ideally during what passes for our summer heat  .  I am certain that I have seen naturally-occurring adult BSF around here before, with those yellow legs.

I am also hoping to get a greenhouse into operation this summer, and possibly even getting some grubs to change into adults in it and lay eggs so I can work up a larger supply (at least enough to keep themselves warm in winter). 

If the cycle from egg to adult requires 38 days at 84°F (29°C), and I can keep the bucket warm enough by leaving it in the sun, I might be able to get several batches to adulthood instead of just one.

Any opinions?  Do you think this might work?

Sue

[GW]

I think everything you wrote makes sense Sue. I've told people in cooler climates that keeping their BSF in the shade might not be the best approach, at least until the point where you reach a good density of larvae. As a rough guess I would say that ambient temps in the 70s (20º-24ºC) would be ideal for a dense colony that is being fed regularly. Under those circumstances overheating wouldn't be the concern that it is for we who live in hotter climates.

Most BSF culturing has been done in regions where hot weather is the norm. This is why the general rule of keeping a BioPod in shade was created. The more basic guideline is to aim at keeping the internal temp of the colony in the 85º - 95º (30º-35ºC) range. The acceptable range of temperature is broader of course, but I think the range I gave is a good balance between being warm enough to have a high metabolic rate and being safe from the lethal temperature of about 115ºF/46ºC.

I think a greenhouse would be a great tool for extending the BSF reproductive season in your area. I look forward to seeing what you can accomplish this summer.

[Andrew]

Sue, I will be doing the same thing in early Spring, but may find a location that gets partial sun as the weather warms up. I think most of the research on BSF has been done in very warm climates. I don't know if the "cycle from egg to adult requires 38 days at 84°F (29°C)" holds for those of us in cooler climates. Certainly the average temps for ovipositing ("... 99.6% of oviposition in the field occurred at 81.5 F to 99.5 F") must be lower in our climates. I think it's very possible that you will get multiple generations this year.

[BelgianPup]

"I don't know if the "cycle from egg to adult requires 38 days at 84°F (29°C)" holds for those of us in cooler climates."

Very true, but at least it wouldn't be any FASTER than that!   

I am also curious to find out if our cool nights will slow their growth even with warm days.  I will try to maintain good observation and note first eggs to first adult.  If it is much more than 38 days (and it think it probable), I will know that constant warm temperatures (night and day) is optimum, and not possible here until the number of grubs is high enough to generate their own heat.

'Twill be an interesting experiment. 

Sue