Thursday, November 3, 2016

Mealworms raised outside with Passive Solar Heating

I've found mealworms (Tenibrio molitor or Yellow Mealworm) can be raised in black plastic containers outdoors in a temperate climate provide the containers are in a sunny position causing them to heat up during the day. A simple, basically free, form of passive solar heating.

Mealworms of course require heat (and darkness) to survive and flourish but they are also surprisingly tolerant of temporary cold. They survived all winter outside in the containers here, where the night temperature typically drops to between 5 C and -3 C (zone 9, Wellington, New Zealand).

By contrast when I tried raising them inside the house, including above the water heater, this quickly failed, presumably because it was not nearly hot enough.

I had to secure the containers with wire mesh to stop them blowing away in the wind. I also taped screening around the lid to prevent the adult beetle from climbing out, I'm not sure this is necessary they don't seem to have thought of that so far. 

Another problem was figuring out if the containers were safe for raising insects in, unsurprisingly there is not much info on plastics suitable for insects. Some manufacturers market containers as "food grade", suitable for keeping food in, which I took to be ok, but finding one that says that and is black may be difficult. I resorted to buying a blue "fish bin" (for keeping fish in, presumably safe) and painting it black. It might even be possible to make a container out of wood and paint it black if you don't like plastic. 

I just feed them grass and weeds from the garden I know to be edible for humans, reportedly they will eat anything that is rotting.  

I have never raised mealworms with the usual artificial heat so can't compare productivity of outdoor containers with this. So far, I've only had them just over a year, they appear to go through one life-cycle a year.

I haven't spent much time on trying to complete the life cycle, from adult beetles to eggs and so on. Some websites say the beetles will eat their own eggs, I have not found this in any of the books I've found on the subject. Last year some eggs hatched after being outside in the box for winter when I didn't take the precaution of removing the adult beetles to stop them eating the eggs. This year this doesn't seem to have worked so far. Next time I'll try cleaning the boxes which I probably should have done (1.2.) I can't imagine experiencing comparatively mild Wellington winter temperatures is the problem given the much harsher places they are found in the wild.

My interest in mealworms is as part of my own diet and part of an effort to produce most of my own food on a small section. Mealworms appear to contain all the essential nutrients fruit and vegetables lack, so could possibly be a wise addition to a small self-sufficient homestead that can't fit larger animals. 

I tried eating a few the other day, after fasting them for 24 hours. I fried them in olive oil, they were crisp and melted in the mouth, not much to them. I suppose they were a little like the skin of Kentucky Fried Chicken, not bad, but bitter as well, something I fed them perhaps, or the oil? Will have to do more work in this area.

Footnote. What Wetas taste like.

While on the subject of eating insects, thought I'd answer the question "what does a Weta taste like?" I once found a Tree Weta in the bush lying on its back wriggling slowly, I brought it home, it died shortly after. I chewed the body, without cooking it, then spat it out and rinsed my mouth. It tasted exactly like Rotorua smells, like sulphur. I think it is remotely possible a taste could be acquired for it, people live in Rotorua after all. Aside from the exoskeleton it had the consistency of puss. Early Maori ate them but reportedly mushed up with other things (3) probably to mask the taste and texture.  

I defer to Weta experts I've contacted who say we should not eat Weta for conservation reasons. It's possible a case could be made for farming them but I'm not interested in that fight. I also recall reading they can be infested with parasites, it is possible these parasites could be very harmful to humans if they or their eggs were eaten alive.

1. Culturing Live Foods. Michael R Hellweg 2008
2. Eat this Bug. Lynn Davis 1996.
3. Which New Zealand Insect? Andrew Crowe. 2002 

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