Health problems
Like all animals, mantids can suffer from a number of ailments. Understanding the problems and causes can help to keep your mantis happy and healthy.
Maintaining good husbandry will prevent many. issues.
Not Eating
Nearly everything on this list can cause a mantis to not eat. If the problem just started and your mantis has a large abomen, it could be they are getting ready to molt of they are just not hungry. Give them a few more days and then offer food.
If they just molted, or are still a ways away from molting, it's time to look at other issues. First check your setup. Check that you have your mantis at the correct humidity, and temperature. Be sure their enclosure is clean and look at the overall body condition. Check for external parasites or wounds.
Try to offer a different variety of food items. Sometimes something new will peak their interest. Some species will reach a particular size and refuse a smaller prey item.
Lastly you can try to force feed your mantis. Take a large and juicy mealworm and cut it in half. Using tweezers, hold the cut end to the mantis mouth. Mantids will naturally start trying to chew. Once they realize its food, they will grab it. If they push it away, try again in 2-24 hours.
Improper feeders and incorrect feeder size
Some species of mantis require special diets. Orchid mantis, Thistle mantis or wandering Violin require flying insects and can't digest crickets.
Feeding improper feeders can cause a number of health issues from improper molts, infertility, or even death. Same can be said of feeding the wrong sized feeder.
One issue most inexperienced keepers have is using fruit flies for too long. Mantis receive much of their moisture from feeders. After they reach a particular size, fruit flies wont provide the required amount of moisture or nutrition. It takes more energy to catch and eat than they receive.
Provide feeders that are 1/2 the length of the mantis.
Bad Feeders
Bad Feeders can be common as many large chain pet stores keep their feeders in poor conditions. These can introduce bacterial, viral infections, or parasites that can make your mantis sick.
Because Mantids are insectivores, pathogens from one insect can often transfer to each other very easily. When selecting feeders, be sure the container has no dead insects. Crickets are notorious for caring pathogens and parasites.
You can breed and grow your own feeders to ensure quality and save some money. Roaches, meal worms, and fruit flies are very easy to keep with plenty of recipes for fly cultures online.
Keep your feeders well feed and healthy and you will have a healthy mantis.
Feeder Poisonings
There is controversy of crickets and roaches gut-loaded with carrots being a source of poisonings in mantids. There is very little research into this theory and many factors can take part of why a mantis falls ill. Some reports are of mantis vomiting after eating but then recovering, while others have shown no effect. Some report the compete opposite with a mantis growing weak and dying within a day or so.
Overall the best course of action is to just avoid carrots for feeders and gut-load for 24 hours prior to use. A good quality source of food and water will flush out anything they may have digested before purchase.
Apples, potatoes and oats are an excellent food source for all feeders.
Vomiting
Vomiting in a mantis can be one of several things. The color of the vomit is the best indicator for the problem. It will appear as streaks or splotches on the side of the enclosure.
-Clear vomit is just excess water.
-Red vomit is caused by the mantis eating too many fruit flies and is typically harmless.
-Brown vomit is most often the result of overeating but could be a sign of blockage.
-Black vomit is usually a viral or bacterial infection and will most often result in death.
The best treatment for vomiting is to provide a clean enclosure, good quality and well fed feeders, and clean water. The mantis will either improve or pass.
Infections
Bacteria infections can also affect your mantis and cause disease. Making sure you feed your mantis harmless prey can prevent infections from bites or stings. Scratches and wounds from the environment can also cause infections. A common injury can be a scratch to the eye or mouth that becomes infected. An infected eye can cause blindness resulting in the inability to hunt. Keeping your container clean can prevent this.
An infected body part will start to turn black, spreading from the wound site. At this point there is nothing to be done.
Viral infections are also possible and are often introduced by new insects into the area. It can sometimes be introduced by prey items. Keeping your mantis in a clean environment and with a varied diet will help to keep it healthy and fight off diseases.
Black Spots On Eyes
Black spots on the eyes is known as "Eye Rub" This is caused my the mantis rubbing its face against the side of the enclosure.
It's often caused when more than one mantis is kept within close proximity to each other. They become fixated on the mantis next to them and result in scratches to their eye from rubbing their head. Its fairly common and usually not an issue. It's mostly seen in older adult mantids
Eye rubs can become infected and quickly spread to the rest of the mantis resulting in death. If you see your mantis doing this you can put a little divider between them. keeping your mantis cage clean will help prevent infections. if still a nymph, the damage will repair each molt but vision in that location will not be restored. Thankfully mantids have thousands of lenses in their eye allowing them to still see quite well.
Parasites
Parasites can be introduced by feeders. It can stunt their growth or even kill your mantis. Making sure you have a good supplier is important.
The most common known is the Horsehair worm Nematomorpha which manipulate the host to jump into water so it can escape and reproduce. Pet mantis don't often come across these as much unless they are being fed wild insects that happen to be infected. Avoid aquatic based insects such as mayfly.
Mantises can also be infected by other parasitic like wasps, flies, beetles, that use the mantis as a host for their larva, laying there eggs either inside or on the surface of the mantis abdomen. The larva will eat the mantis from the inside out before resulting in its death. Some wasps will parasitized mantis eggs. They can also be infected by fungi, and other types of worms.
With your mantis indoors, parasitic insects are not much of an issue. Less so if you keep them in a container with fine ventilation holes. Window screening is small enough to keep out smaller wasps.
Mites
Mites can sometimes grow in fruit fly cultures and end up in with your mantis. They can show up on the face, eyes and legs preventing the mantis from hunting or eating. Check your cultures for mites before using them.
Most mites are harmless and only stay on a mantis in unfavorable conditions, hoping they will carry them to a more hospitable environment. Some mite species can be parasitic, but are very uncommon in this hobby.
One or two mites are not much of an issue and will fall off with a molt. The problem arises when the mantis is heavily infested and can no longer see or move to hunt. There is no treatment for a heavily infested mantis.
Throw out all contaminated objects, and clean your surfaced with vinegar to prevent mites from continuing to spread. Contaminated fruit fly cultures should be thrown away. Cultures can stay in a light dusting of diatomaceous earth to prevent mites from infesting containers.
Improper Molts
failed molts are a very common cause of death. It’s often cause by too little/too much humidity, a fall while molting or an injury. Some mantis can survive and correct the problems with consecutive molts, but it depends on the severity.
Providing good nutrition, proper humidity levels, places to hang with enough space can prevent most bad molts.
If you see your mantis has fallen, gently place them back up in a open spot. If the mantis is stuck in a molt try give the enclosure a gentle spray with water without hitting them directly to help. Sometime a gentle hand and a damp Q-tip is needed to remove the excess exoskeleton.
Death after Molt
Sometimes a molt looks like a success. The mantis is moving around normally, but over the course of a couple days they grow weaker until they fall and pass away. Molting is the most dangerous and vulnerable periods of a mantis life cycle. There is little room for error. When they pass unexpectedly within a few days of molting is often the result of something going wrong during the molting process. With their exoskeleton soft they are more vulnerable to internal damages or loss Hemolymph. These damages are usually imperceptible to our eyes.
Unlike humans, mantids breath through passive diffusion using a system of tubes inside the body called tracheae. They are connected to the outside by holes in the side of the abdomen called spiracles. During the molting process, a mantis will also shed the inner lining of their tracheae. Though not common, the shed lining can detach resulting in the mantis tracheae becoming clogged. The mantis slowly suffocates. There is no treatment for this and will most likely result in death.
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Loss Of limbs or Wounds
Sometimes during a molt, one or more of the mantids limbs is damaged, trapped or severed. Even with one or sometimes two limbs missing, a mantis can typically move around quite well. If one or both of the raptorial claws is damaged or lost, it can result in starvation of the mantis.
As long as the mantis is still in its nymph stage, limbs will regrow over each consecutive molt until its fully reformed. A full grown mantis can not regrow any body part as they no longer molt.
You can provide supportive care for mantids with damaged claws by hand feeding until their next molt. Wounds can also be repaired after each molt.
Lack of Airflow
Lack of air flow can also cause problems. Stagnant air in your enclosure will not only promote the growth of mold, some species require more airflow to even survive. Orchid mantids have been known to drop dead due to the lack of airflow.
Make sure whatever you use as their enclosure has some form of decent ventilation. A mesh lid or a mesh butterfly enclosure is not always the most aesthetically pleasing but can be what's best for some species.
Too Hot or Too Cold
Insects are ectothermic meaning they don't produce their own heat and rely on the environment to thermoregulate. Some species are very sensitive to temperature fluctuations while others are very flexible.
Keeping your mantis in the range of their natural environment is important to keeping you mantis healthy. Too much heat can kill your mantis, same with cold. Cooler temperatures causes their metabolism to slow and growth to become stunted.
Collapsed Abdomen
Collapsed abdomen syndrome is when the the abdomen collapse in on itself behind the legs, resulting in poor nutritional intake and hindering the ability to defecate.
I've seen this mostly with Chinese Mantis, whom seem to be more predisposed to it. It has turned up once or twice in other species, typically those with long abdomens and once in a membranacea.
Though it's debated on the cause, most agree that its the result of bacterial infections caused by bad feeders. The mortality rate is around 75% but some can be nursed back to health with diluted bee polling and honey powder water. The issue will resolve over a couple molts depending on severity.
Molds
Mold is a killer and should be avoided at all cost. Keeping your terrarium clean and well ventilated will prevent the growth of mold. Hot water and bioactive cleaning soap/ sanitizer can be used to clean out your terrarium.
If you are using some kind of soil or moss, springtails and isopods can be added as a clean up crew to reduce the buildup of waste and prevent molds.
Sudden Death
Sometimes you can do everything right and still you find the mantis dead on the ground. Usually some underlying health issue is the cause. Animals are very good about hiding ailments.
For adults, males will live a substantially less amount of time than a female. Paired females tend to also live a bit longer than unpaired females.
Insects produce hundreds of offspring as many don’t make it to adult. Predation, or disease kill off many of them. Insects go for quantity over quality, spending most of their energy producing as many nymphs as possible. Even in the best conditions not every mantis can make it to adult. It's best to not punish yourself for something beyond your control.
