Frustrations in beetle breeding: dealing with pests

Sometimes there are unwanted scavengers or parasites in the substrate that will negatively impact the growing process or metamorphosis of your beetle larvae.

Here’s a list of unwanted guests and what I do to remove them.

  • fungus gnats (Sciaridae):
    annoying little flies that reproduce in the soil. If you have some houseplants, you’ve probably already met them: A tiny fly, similar to a fruit fly but smaller and completely black. They lay their eggs in the soil and their larvae feed on your precious beetle substrate. The larvae are a cream color and about as thick as a hair. They eat substrate along with your beetle larvae, but worse than that they will sabotage the beetle pupa while inside the cocoon.

    – predatory mites Hypoaspis miles to add to your substrate. They are fast moving soil dwelling mites that will eat the gnat’s eggs and larvae as well as keep your beetle larvae clean of parasitic mites.
    – yellow sticky cards in the beetle room. Flies and other diptera are attracted to the color yellow. They land on the card and stick to it. It’s just glue, no poison or pesticide involved and hence safe for your beetle larvae. You can stick one on the underside of the lid of your rearing box. For obvious reasons you can’t use this with adult beetles that fly.
    – a bug zapper. The gnats (and other pests) are attracted to the UV light and get an electric shock when they land, killing them instantly. You can put it on a timer so it always runs at night and you don’t have to remember to switch it on.
  • fruit flies (Drosophilidae):
    These small funky eyed flies appear when you regularly feed fruit to your adult beetles – especially in warm summer months. Needless to say they love bananas. Just like gnats they are tiny enough to move in and out of terrariums and breeding boxes as they please. But these guys just breed and lay eggs on the fruit, rather than in the soil.

    -sometimes prevention is better than the cure. Remove fruit after a day. Fruit flies will also turn any fruit sour after 2-3 days. Remove it so the eggs they lay on the fruit have no chance to hatch. You can even put it in the freezer for a day first if you want to avoid them hatching in your trash bin.
    – a funnel trap. Pour some beer, or wine in a glass or transparent cup. If you want to go all out you can even put in a piece of banana in the liquid. Roll a funnel out of paper and tape it to the glass or cup. Make sure the entrance hole of the funnel is about 1mm. The flies will get in, but won’t be able to get out. After about 24hrs you will start to witness a true fruit fly get together in the glass. Once the party’s going they will only attract more of their kin.
    – the trusty ol’ bug zapper which you already purchased to zap gnats :’)
  • parasitic/static mites:
    They tend to appear in wet, poorly ventilated boxes, or in boxes where you supplement a lot of protein. They can cling to larvae as well as beetles and may obstruct mouth parts, prohibiting the larva to feed. All in all they are an annoyance and a risk.

    – predatory mites
    – keeping your boxes clean, well ventilated and dose protein supplements according to need
  • earth worms:
    not really a huge problem, but they eat your larva’s food at a much faster pace. If left unnoticed they will also reproduce until all food is eaten by their family members and starve your larva.

    – I honestly just pluck them out by hand if I come across one while refreshing substrate.
  • Megaselia coffin flies (Phoridae):
    They are nicknamed zombie flies or coffin flies and are probably the worst thing you can encounter in your breeding room. They are a parasitic fly and feed on your larvae and beetles from the inside out. They are not much bigger than an ordinary fruit fly, but they have a white belly and a humpback. You can also tell by the way they walk – they are great fliers but when they walk they just move in short bits, stopping after every 2 seconds. They can smell a recently deceased beetle or sickly larva from a huge distance and will lay their eggs on it. The fly larvae will then eat out the host. Whatever animal they colonize will develop a “cheesy” distinct smell. They have no problems crawling into substrate, or the tiniest cracks of a box or breeding room door.
    You will often not notice their presence until you come across a few of these white bellied flies. Or you will notice their larvae when they crawl out of a recently dried specimen to pupate and form tiny brown elliptic shaped cocoons.
    I encountered them one summer after purchasing infected larvae from another breeder. I can tell you that summer was a nightmare, but I managed to eradicate them in a few weeks.

    – time to panic and act immediately. Run the zapper on 24/7. Check all boxes and replace substrate. Quarantine any boxes that you suspect may have infected larvae or beetles. Do not leave dead beetles to dry – rather freeze them.