The larvae of the Black Soldier Fly (Hermetia illucens) are readily consumed by a wide range of pets and farm animals including birds, fish, reptiles and amphibians. Resident here in New Zealand in only small numbers, most people would be lucky to see an adult fly in the wild – and even luckier to see a larvae (they are photophobic). Now that you know what the adults look like, I’m sure you’ll be seeing them everywhere.

Grubs Up started its colony from a wild colony and has since optimized the conditions for adult mating and larvae growing. Maybe not that unusual, adult flies will only mate in the same conditions that some humans find irresistible for mating – hot & sultry. The Grubs Up colony also consumes the same food that us humans eat – meat and three veg, or fish or fruit is just fine for these guys. They may even eat healthier than some humans. And its all food waste being diverted from landfill into a little energetic grub packed with nutrition.

A quick biology lesson – lifecycle of the black soldier fly

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The lifecycle begins as an egg (or maybe as a fly?) which is incubated into a creamy larvae. One female fly will lay anywhere between 300 and 700 eggs in her single clutch, and (to give perspective) this clutch is not much bigger than a pin-head. After hatching, the larvae are very active, have voracious appetites and will readily consume a wide range of foods for between 2 and 3 weeks.

 
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About 4 weeks after hatching the larvae begin to darken into pre pupae. They are not as active and will not consume quite so much food. They are starting to think about life as an adult fly, conserving as much energy as they can for the morph that awaits them.

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As a pupae that now looks almost black, a hard exoskeleton has formed and the insect will appear lifeless. It will not eat again in its lifecycle (adult flies only drink).

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Adult flies can take several weeks in the right conditions to hatch out, find a mate, lay eggs and the lifecycle completes.

 

Packs of grubs

Sold live in kraftboard tubs or dried in stand-up pouches, Grubs Up caters to both ends of the squeamish scale.

 
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Live larvae are generally 2 or 3 weeks old and 15 to 20mm in length when they are packed for our customers (we can supply smaller insects from 5mm in length if requested). They have not yet matured into pre-pupae and have a sufficient food source packed with them in the tub to keep them happy for 3 or 4 more weeks. At this stage of their life, the larvae are readily taken by a wide range of animals all intrigued by their fast wiggle. For those aquarists, these larvae will sink slowly in water, making it an ideal food for fish that fed at different levels in the tank. Larvae can grow up to a length of 25mm.

Once the grubs start to mature into pre-pupae and then pupae, they form a harder exoskeleton which might make them more difficult for some animals to eat, although we are reliably told that many birds still tuck in. As the pre pupae get increasingly darker, they become more buoyant, making them more ideal to aquatic animals such as top feeding fish and turtles.

Eventually the pupae will hatch into an adult fly, although this could take 6 to 8 weeks after the grub has turned into a pupae.

 

Dried larvae are available in stand-up pouches with a resealable zipper to keep them fresh. The pouches also come with a moisture absorption sachet. This should not be considered food (a very puckered-looking animal may result)!

Dried larvae are generally between 15 and 25mm in length and can be fed whole (we know even small finches pick away at them) or crumbled into a pond or aquarium. The company’s goldfish is testament to this being considered a good dinner - or maybe it just forgot what its last meal was.

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Live grub care

Where possible, keep the tub above 15ºC. They will survive at temperatures below 15ºC however may appear lifeless – they will start to move again once placed back into a warmer spot. Add a teaspoon of water when the media gets dry and stir it in (the media does not need to be “moist”). Ensure the lid is kept on the tub otherwise they will escape – they are expert climbers! No additional food needs to be provided.

 

Grub nutrition

High in protein and fat, some fibre and low carbs – black soldier fly larvae could the animal-world’s version of the Paleo diet. Afterall, your pet was probably consuming insects long before the words “convenience” and “processed” were put together.

The boffins at Massey University tell us larvae from the Grubs Up colony typically contain 45% protein (dry weight basis), which is similar to salmon or chicken, and is rich in minerals including calcium, zinc, magnesium, iron and manganese. For those of you having to dust other insects with calcium before feeding, this is not required for black soldier fly larvae.

Amazingly, the fat profile of black soldier fly larvae is very similar to coconut oil – including being high in fatty acids like lauric acid. Lauric acid makes up about 50% of the fatty acids in coconut oil and contributes to almost 60% of the fatty acid profile in black soldier fly larvae. High levels of lauric acid are proven to have antimicrobial properties.

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