Mecynorrhina torquata is one of the largest flower beetles (Cetoniinae) in the world. Males can reach 8-9cm and come in a range of colour forms, from olive green to deep burgundy, often with a white or cream dorsal stripe. Females are smaller and less variable but still chunky beetles by any standard. They're from equatorial Africa and, in the wild, adults visit flowers and feed on sap and ripe fruit.
This is not a beginner beetle. If you've kept Pachnoda and maybe a rhinoceros beetle species, and you're comfortable making or sourcing quality flake soil, then M. torquata is a good next challenge. If you haven't reared any beetles yet, start with something more forgiving.
Adults
Adult M. torquata are impressive. Males have a small cephalic horn that they use for shoving matches, though it's nowhere near as dramatic as Dynastinae horns. Both sexes are strong fliers and surprisingly loud in flight. They're active during the day, which makes them enjoyable to observe.
House adults in a well-ventilated enclosure. A 15-20 litre container is adequate for a pair. Provide bark, branches, and a shallow layer of substrate. Ventilation matters because these beetles are active fliers and generate heat; stagnant air combined with warm conditions encourages mould.
Feed ripe banana, mango, beetle jelly, or other soft fruit. They're enthusiastic feeders. Remove uneaten fruit within 48 hours. Adults live roughly three to five months.
Breeding
Mating happens without intervention when males and females are housed together. Females need deep, moist, firmly packed flake soil to oviposit. Fill the breeding container with at least 20cm of substrate, with the bottom half compressed firmly. Females burrow deep and lay eggs individually.
A productive female can lay 30-50 eggs over her lifespan. Keep the breeding container at 24-26C. Check for eggs and small larvae after three to four weeks by gently sifting through the substrate, or leave them in situ and separate larvae once they're visible at L2 size.
Larval care
This is where the difficulty level goes up. M. torquata larvae are sensitive to substrate quality in a way that Pachnoda larvae simply aren't. They need well-fermented, high-quality hardwood flake soil. If the fermentation is incomplete, or the wood species is wrong, or the moisture level is off, larvae grow slowly, fail to put on weight, and often die during L2 or L3 without obvious external symptoms.
The larval period is roughly 8-14 months depending on temperature and substrate quality. Larvae are large at maturity, with L3 grubs reaching 10-12cm and weighing 30-40 grams. They need individual containers of at least 3-5 litres per larva, filled with packed flake soil.
Temperature is important. Keep larvae at 24-28C. Below 22C, growth slows dramatically. Above 30C, you risk killing them. Consistent warmth is better than fluctuations, so a heated room or a heat mat on a thermostat is a good idea during cooler months.
Top up substrate regularly. These larvae eat a lot, and an L3 grub can work through a litre of flake soil in a few weeks. Don't let them sit in mostly-consumed substrate for extended periods. When more than half the container contents look like dark frass, it's time for a change.
Substrate quality
I want to come back to this because it really is the determining factor with M. torquata. The flake soil needs to be made from properly fermented hardwood, ideally oak or beech, with a good white-rot fungal colonisation. The finished product should be dark brown, soft, crumbly, and smell earthy. If it's pale, hard, or smells sour, it's not ready.
Some keepers add a small percentage of protein supplement (soya flour, brewer's yeast) to the flake soil for Mecynorrhina larvae, claiming it promotes larger adults. Opinions vary on whether this actually works. If you try it, keep the protein content low, around 1-2%, to avoid attracting grain mites or causing the substrate to go off.
If you're buying flake soil, buy from a supplier whose product has a good reputation with Cetoniinae breeders specifically. Not all flake soil sold for beetles is equal, and the cheap stuff that works fine for Pachnoda might not cut it here.
Pupation
Mecynorrhina torquata larvae build large, solid pupal cells. The cell needs enough surrounding substrate to support its structure, so make sure the container is deep enough and well-packed. As with all beetles, do not disturb the container once the larva has gone pre-pupal.
The pupal stage lasts about four to eight weeks. After eclosion, the adult remains inside the cell for a further few days while its exoskeleton hardens. Eventually it digs its way out. Newly eclosed adults may be quite pale and need a week or more to fully colour up and harden.
Colour variation
One of the main draws of M. torquata is the colour variation. The subspecies M. torquata ugandensis is the most commonly kept form and comes in a spectrum from green to orange to deep red-brown. Colour is partly genetic and partly influenced by rearing conditions, though the exact relationship isn't well understood. Selecting breeding pairs based on colour can push subsequent generations toward particular colour forms, which is part of the appeal for collectors.
Common issues
Larvae dying at L2-L3 with no obvious cause: Almost always substrate. With M. torquata this is the default failure mode. If your larvae are consistently dying or not gaining weight, change your flake soil source before changing anything else.
Small adults: Substrate quality and temperature. Larvae reared on mediocre flake soil or at temperatures below the optimal range produce adults that are a fraction of the size they could have been. The difference between a 5cm male and an 8cm male is almost entirely down to larval care.
Adults not mating: Make sure they're fully hardened and at least a week or two past eclosion. Newly eclosed adults need time before they're reproductively active. Temperature should be 24-26C. If they're still not mating, try separating them for a few days and reintroducing.
Keeping M. torquata well is one of those things that separates casual beetle keepers from people who are properly into it. The payoff is a beetle that looks like it belongs in a natural history museum, walking around your desk eating banana.