Wednesday, February 17, 2021

A Short Guide to Pests & Other Microfauna

Bit of a different post, (one that I'll add more pictures to over time), today I'd like to just go over some of the more commonly encountered pests and other microfauna people will find in their invertebrate enclosures, as well as some tips on deterring them. I hope this post proves helpful and informative to invertebrate keepers of all kinds! 😁


Perhaps the most notorious of the pests one can encounter in this hobby, there are many different mites that can breed in invertebrate cultures, some of which are harmful, others more neutral or even benign. 

Grain mites (Acarus siro)

Grain mites, free roaming feeding stage.
The worst of the pests mites IMO, and one of the most commonly encountered. These gross, white, spherical, slow-moving mites are attracted to all manner of decaying organic matter, and in captivity are most commonly attracted to rotting grain products, as well as rotting produce and dead invertebrates. Basically, any leftover food your inverts don't eat is fair game, and a small portion of food can sustain hundreds or thousands of mites. Their free moving stage is their most harmless one, but as their numbers reach plague proportions, and either they feel too crowded or conditions become unfriendly towards them, they'll latch on to any solid surfaces they can (including your inverts), and enter what's called their "hypopus stage", at which point they become living, immobile suction cups. They'll stay in their hypopus stage until they sense conditions are good to let go and become free roaming again. They can clog up mouthparts, leg joints, and breathing spiracles on the invertebrates they cling to, and can severely stress and even kill inverts in this way. 

Grain mites in their hypopus stage, clinging to a Carabus nemoralis beetle
These mites prefer humid conditions and are attracted to uneaten leftovers, as well as dead invert bodies. Their eggs can be found in most grain based pet foods and mites can also be clinging onto inverts you just acquired, and thus are difficult, if not impossible to prevent from coming into a collection at some point. They can be controlled by keeping enclosures dryer and better ventilated, reducing the amount of food you feed your inverts so that there are less leftovers, removing leftover food after 48 hours, or by using predatory mites in your enclosures. A cleaner crew mixture of springtails and Oribatid mites can also take up the same ecological niche grain mites inhabit and prevent them from reaching plague proportions in an enclosure.

Once grain mite numbers reach the thousands and they start clinging to your inverts and the sides of the enclosure in their hypopus stage, or if wandering mites completely fill the substrate and cover the walls of the enclosure, you'll just need to completely clean out the enclosure, replace the substrate and everything. There's no good way of controlling them at that point, you'll need to start fresh and take preventative measures for the next time.

Recently I've come across a similar type of mite, which I've been calling Yellow Mites. This is a new species for me, they act much the same as grain mites, but are smaller, yellow, and have a matte exoskeleton texture rather than a glossy one. Prevention methods are much the same, though they only seem to bother very tiny inverts, and aren't as prolific as grain mites. No idea as to their identity unfortunately.

Oribatid mites (Oribatida)

Sometimes referred to as "soil mites" or "beetle mites" due to their rounded, hard shelled appearance, these are common in humid invert enclosures in the hobby, but a lot of people might not even be aware they have them in their collections. They are dark, hard shelled, secretive mites that you'll generally only notice much if their populations are very high, which doesn't happen all that often compared to other mite species. Oribatids are typically a dark red color, though species can range in coloration from reddish brown to black. 
I consider these a lesser evil and technically beneficial in some cases, they take up the exact same ecological niche as grain mites do, eating leftover supplemental foods and such, however they don't have a hypopus stage, and generally shy away from larger inverts, which makes them a lot less dangerous than grain mites. 

Red Oribatids in various stages of development, alongside silver springtails
However, they can reach very high populations if uneaten supplemental food is touching the substrate consistently, (they have difficulty getting into food bowls, unlike grain mites), and can potentially swarm food that touches the substrate before your inverts have the chance to eat it, causing your inverts to starve... They'll also stress out smaller invert species if their numbers are too high with frequent tactile contact, and the food swarming, and I've had them nearly wipe out small Ectobiid roach cultures before.

Red Oribatids
All that's needed to prevent them from reaching high populations is to not leave uneaten food on or in your substrate, and use food bowls of some sort of possible. If they reach plague populations, then your only option is to remove and replace/sterilize all the substrate and hides in the enclosure, they can handle dry spells better than grain mites, don't mind high ventilation levels, and predatory mites won't eat them, they're too hard shelled. However, they're much slower breeding than grain mites, so their numbers take a while to build up after you've rid an enclosure of them. 

Predatory mites (Stratiolaelaps scimitus, ex. Hypoaspis miles)

Stratiolaelaps scimitus ©Isopod Ranch
These are perhaps one of the most beneficial mite types ever, mainly because they eat other mites, and fungus gnats too! But, they can also cause stress to some invertebrates via constant tactile contact during their population booms, and can even severely stress or kill smaller invert species, (such as springtails, ant crickets, certain Dipterans, etc.).
However, they only tend to stress larger inverts out during their big population booms, which tend to be fairly short lived, as they run out of food at that point pretty quickly, and their populations crash for a little while, until the pest populations in those enclosures go back up. Supposedly they'll eat detritus and random decaying organic material when prey items are unavailable or in short supply, and this is probably what allows them to continue on in enclosures for a while even after most of their prey sources have been exhausted, but they definitely do not thrive on that diet.

Stratiolaelaps scimitus ©Isopod Ranch
As for preventing these mites from entering your collection or a specific enclosure, say a springtail culture (which is an all-you-can-eat buffet for predatory mites), that's rather difficult. These mites are very mobile, can climb smooth surfaces, and thus jump cultures with ease. These mites seem to prefer humid, minimally ventilated setups, so letting things dry out or increasing airflow greatly may dwindle their numbers down. However, that alone might not completely prevent them from popping up in cultures, and generally if there is an enclosure with a food source for them, that is somewhat close to containers that you know have predatory mites in them, it's safe to assume they'll find a way into that enclosure sooner or later.

Stratiolaelaps scimitus
There are other predatory mite species, some that prefer drier conditions, some that are much bigger than Stratiolaelaps scimitus, some that may be far more harmful to a wider variety of invertebrates, etc., but S.scimitus is by far the most commonly encountered predatory mite species in the invertebrate hobby. 


One of the more annoying pests one can have in the invertebrate hobby, though they're often more annoying to us humans than they are to our pets... With only one commonly encountered exception.

Fruit flies (Drosophilidae)

I've never actually had an issue with fruit flies as pests, and I assume most people who claim to have "fruit fly" infestations in this hobby are mistaking fungus gnats or phorid flies for fruit flies... However, if you actually do have a fruit fly problem, then it's probably due to rotting fruits in your enclosure(s)... Remove leftover fruit as it starts to spoil, and/or feed fruits in lower quantities so as to eliminate leftovers altogether, and your fruit fly problems should go away. If for some reason that doesn't work, consider using predatory mites or BTI, (which I'll go more into depth on in the fungus gnat section below).

Fungus gnats (Sciaridae)

Probably the most commonly encountered Dipterans in pet invertebrate cultures, the nearly transparent larvae of these small flies feed on a wide variety of decaying organic matter in/on moist substrates, including rotten wood, dead leaves, compost, leftover supplemental foods, dead invertebrates, etc., with a particular taste for rotten wood and leaves it seems. This can prove annoying, especially for beetle and millipede breeders, who need a humid, very organically rich substrate for breeding, which is a fungus gnat haven. They're commonly encountered in smaller numbers in a variety of invertebrate enclosures, but scarab beetle and millipede enclosures can produce clouds of fungus gnats in a very short time frame, not very pleasant for most of us breeders, considering they seem to love flying up human noses and into eyes as well... 

They very seldom stress or harm larger invertebrates directly, however they can eat vast quantities of rotten wood and leaf litter in a very short amount of time, which will lead to scarab larvae and millipedes starving unless you replace the substrate for them. Mostly they're just annoying to deal with and to inhale as you're doing maintenance, and unfortunately they are a pest nearly EVERY invert hobbyist deals with, due to the fact that there are fungus gnat species nearly everywhere, and they can fit through most window screen, so they will inevitably find their way indoors and then seek out humid areas to lay their eggs, (like in your enclosures). They may also be brought in with unsterilized wood and leaf litter materials, as well as potted plants, (they feed on the potting soil).

As far as preventing fungus gnats from taking hold or reaching plague proportions in your enclosures, there are a few things that can be done. They despise dryness, and so letting the substrate dry out a bit can kill a lot of their larvae off. Additionally, if you remove leftovers frequently, you can limit their numbers in enclosures where supplemental foods are their main source of nutrition. 
However, in humid enclosures with a nutritionally rich substrate, your best lines of defense against fungus gnats are predatory mites, or the bacteria Bacillus thuringiensis israelensis. Predatory mites can decimate fungus gnat populations given a little time, and are the probably the main reason I've never had big fungus gnat issues. Bacillus thuringiensis israelensis, (BTI) is a strain of bacteria commonly sold as "Mosquito dunks" or "Gnatrol", that when ingested, paralyzes and kills various fly larvae. It seems to only target fly larvae, and so is harmless and safe to use in most pet invertebrate enclosures, many keepers swear by it. However, it seems a less sustainable option than predatory mites, at least, you'll need to keep on buying BTI again and again as you kill off all the gnats and they inevitably come back, whereas with predatory mites you should always have some of those in your collection unless you try to exterminate them.
Roachcrossing also sells fungus gnat specialist rove beetles, Dalotia coriaria, which can be quite effective in feeding on and removing fungus gnats from enclosures, much like predatory mites.

Phorid flies (Phoridae)

Sometimes called "hump-backed flies" or "scuttleflies", these little pests are most commonly encountered by roach breeders, and are larger than most fungus gnats. They feed mainly on dead invertebrates, with a particular fondness for meaty, somewhat soft bodied ones, (like roaches). While they may seem like harmless scavengers, females will actually lay eggs on live roaches that are either weak or injured, and their larvae will sometimes start consuming and then kill said roaches...
In large numbers their feeding activity can turn roach bodies, frass and leftover food into mud essentially, which when moist gets anaerobic and can cause further die off in roach colonies, further fueling the flies and making the situation even worse.
They really seem to highly stress out roaches and can turn a filthy, crowded roach colony into a filthier, but far less populated roach colony pretty quickly if left unchecked... They essentially take a bad situation and make it much worse. 

Predatory mites and BTI might work to thin their numbers out, and phorids don't handle dryness the best, but thinning their numbers temporarily isn't good enough, and the larvae can survive temporary dryness if they're inside a plump rotting roach body. The best thing to do when you have a phorid fly infestation is to completely clean the enclosure, remove and replace all substrate, and either replace or sterilize all hides to get rid of any pupae attached to them. Staying on top of things and removing dead bodies from your enclosures weekly as needed will eliminate their food source, preventing phorid flies from taking hold. So long as you keep your enclosures clean of body buildups, you shouldn't have big phorid fly infestations.


The nematodes most will be familiar with are somewhat uncommonly encountered, tiny worms that pop up in enclosures rich with organic matter, hitchhikers on unsterilized materials. Most varieties encountered in captivity are fairly harmless, though if their numbers somehow reached plague proportions, I can definitely see them stressing out certain invertebrates, and it's possible in large enough numbers they could damage molting invertebrates and attempt to feed on them... But I've rarely seen such reports, and nematodes seem somewhat easy to eradicate by replacing, sterilizing or completely drying out the infested substrate/hides and cleaning out the enclosure.

Horsehair worms are a type of parasitic nematode that some people may encounter, typically found in wild caught Orthopterans, as well as related insect groups. When they reach maturity, they force their hosts to seek out water to drown themselves in, after which the several inch long, very thin worm comes bursting out, looking for mates in the same water source. Since the rest of their life cycle is quite complex, requires a water source and suitable aquatic hosts for their younger larval stages, this is a pest one will only ever encounter with WC specimens, and can not be spread from pet bug to pet bug in captivity without a lot of effort put into doing so. 


Entomophagous fungi

Most truly entomophagous fungi are very host specific and will not be encountered by the average hobbyist, and won't usually spread from species to species either.

However, protein hungry Trichoderma spp. molds can grow within the tracheal and gut systems of some insects, and if left unchecked will kill and consume the infected individuals, acting much like a true entomophagous fungus. This mold can decimate cultures, and is usually brought into cultures via unsterilized materials (leaf litter, rotten wood, soil, sphagnum peat, etc.). Infected insects will often halt all reproductive behavior if they're adults, and individuals from every life stage will die in time, then become rapidly covered in low growing, fuzzy green mold, or white mold that turns green. Oddly, only insects are effected by this mold, isopods seem completely unaffected.
Now, there are many Trichoderma mold species that are completely harmless to insects and will instead feed on other molds and decaying organic matter, including dead insects... So white and/or green mold growing on dead invertebrates alone isn't enough to tell if your culture has the harmful, protein hungry kinds of Trichoderma. Only if you are experiencing very high, otherwise unexplainable die offs in your cultures, followed by the dead individuals being rapidly consumed in mold, can you confirm that your cultures are infected with a protein hungry Trichoderma.

As far as preventative measures go, all you can really do is just thoroughly heat sterilize any and all materials collected outdoors before use in enclosures, such as rotten wood, leaf litter, bark, etc., as well as sphagnum peat and probably some composts that are stored outdoors. Make sure wild insects you catch are kept in sort of a quarantine away from the rest of your invertebrates, as wild insects can be infected with these types of fungi and then die and disperse the fungal spores in the enclosure they're in. Cleaner crews alone are not enough to stop this fungus, as even if one or two spores are consumed by one of your insects, that's enough to infect your whole culture. 

To rid infected insects of protein hungry Trichoderma, you need to keep them bone dry, well ventilated, and offer no forms of protein whatsoever, only fruits and veggies for food. If this is done correctly for a couple weeks to a month, then the fungus should die out completely in the infected individuals. However, some moisture loving insects won't be able to handle this, and may die as a result. But kept humid and hydrated, the fungus will continue to persist in their bodies and eventually kill them anyways. 

Food molds

Food molds come in a variety of growth shapes and colors, and there are countless species the hobbyist may encounter. Most food molds are harmless to the majority of cultured invertebrates, just unsightly. However, some of the more stringy mold types can trap and entangle tiny invertebrates, killing them, so it is best to remove those types when seen. Plus, when food molds over, it's generally a good sign that it's time to remove and replace said foods with fresh foods, lest other pests take advantage of the leftovers as the mold dies out.

Aspergillus sp. on chick feed.
These molds are greatly controlled by cleaner crews such as springtails, which will eat the molds themselves, and to a lesser extent isopods, which may eat the molds but more importantly will eat leftovers the mold would grow on. Removing leftover food 48 hours after feeding usually prevents significant mold growth as well.

Leucocoprinus spp. & other mushroom mycelium

Leucocoprinus mycelium
These types of fungi are more annoying than strictly harmful, as they turn substrate into solid mats of mycelium that a lot of burrowing invertebrate species have difficulty digging through. This can highly stress out burrowing inverts, and if it grows fast enough it can trap individuals that had made molting cells/chambers deep in the substrate. However, non-burrowing inverts, specifically detritivores, usually aren't too disturbed by the growth, and can wait the fungus out until it inevitably withers and dies out. (though this can take months). Some other non-burrowing inverts are stressed out by the fungus though, and will require a complete change of substrate and enclosure cleaning as a result. 

Leucocoprinus mycelium
Preventing this fungus requires you to sterilize all substrates before use, usually it comes into collections via dormant spores in coconut fiber, sphagnum peat, potting soil, etc., which will all need to be heat sterilized before use if you want to be 100% sure they're fungus free. Merely drying the mycelium out doesn't usually kill it, and it will revive when moistened again. Isopods and springtails won't touch it. Once it pops up, in order to completely rid an enclosure of it you'll need to completely replace (or thoroughly sterilize) the infected substrate, and then wash out the enclosure itself with warm water and a little soap or something. Or, just wait a few months and let it run it's course and die out, whatever works for your inverts.


Besides the Bacillus thuringiensis israelensis (BTI) mentioned in the fly section for fungus gnat and phorid fly control, there's really only one noticeable type of bacteria that commonly shows up in collections and has any affect on cultured invertebrates. 

Serratia spp.

Rotting, Serratia covered chick feed next to fresh chick feed
Serratia bacteria feed upon decomposing invertebrates (particularly soft bodied ones like roaches), and leftover food, and turns infected material a shade of bright pink/red. It rarely affects living individuals in any way other than potential discoloration, and can be removed from enclosures with a simple cleaning in my experience. Not much of a cause for concern in invertebrate cultures, but a curious phenomenon some people may encounter and worry is fungus related or something.

Serratia covered chick feed


While technically any large, very prolific springtail could stress out slow growing/breeding, sensitive or otherwise finicky invert species, there's only one I consider a true pest...

Tropical Pink Springtails (Sinella curviseta)

Sinella curviseta
This species is popular in the pet hobby for use as a cleaner crew, and perhaps for some species, they work really well. However, I mostly deal with slow growing, slow breeding, sensitive roaches and other finicky invertebrates, and for me this species has proven just as much a pest as grain mites... They are just FAR too prolific, and when they reach those numbers, they can really stress other inverts out with the constant tactile contact. Not only that, but they can also swarm food and prevent small, fragile species like tiny Ectobiidae roaches from eating... They're also really good at jumping from culture to culture, and can handle a wide range of conditions.
I have gone to great lengths to prevent this species from popping up in my roach enclosures, and really the only way to eradicate this species from your collection is to completely clean out all infested enclosures and carefully move back inhabitants without re-introducing any springtails back in... Best to just not get them as cleaner crews in the first place IMO.

Well, I hope this guide proved useful, I may update it as time goes on and I think of more pests to add, or maybe I'll make a new post in the future if need be, we'll see. Thanks for reading, stay safe, and I'll see you all next time! 😉

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