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This is Diplora, our pet praying mantis.
We have kept praying mantis’ before. Diplora joined the team when she was still very small – to start with we fed her Drosophila (fruit flies) from our compost bin.
Like other insects, praying mantis’s get their shape from a stiff exoskeleton, so to get larger they shed this outer layer from time to time.
Diplora has done this 3 times since we got her and we suspect she only has one more moult to go before she (or he) becomes fully adult.
One of the interesting things about this process (ecdysis) is that the exoskeleton retains a lot of the fine detail of the mantid, but with the advantage that we are able to examine it in detail – because unlike Diplora, the exoskeleton stays still while you have a good look at it.
We have enjoyed looking at details such as the compound eyes, the spikes on the forelegs, mouthparts (mandibles) and their fine antennae.
We have not yet fully captured the process on video, but here is some footage from someone who has (for a different species of mantid).
Compound eyes and pseudopupils
One thing that puzzled us with our mantids was the appearance of black dot in each eye – which isn’t always there, depending on the light. You can see it in the photos above, especially the one at the top. This is known as a “pseudopupil” and is essentially an artefact of the viewer. The compound eyes are made of many cones, with lenses over each. The lenses reflect some light, but in one position, relative to the viewer, no light is reflected, and so a dark spot appears.
This site has a series of photos of all kinds of insects showing this effect.
Our newest pet – Miffie – is a praying mantid. He (or she) is inhabiting a large glass terrarium with twigs to climb, leaves and water. And we are supplying live flies daily.
Miffie doesn’t move a lot, but he does become quite animated when he spots a fly – turning his head to track his target, and often quivering as though excited. Usually he waits for the unsuspecting meal to wander or fly past, then he grabs them with impressive speed, using his two front legs. Occasionally Miffie will stalk a fly before grabbing it. After each meal he pauses to groom himself, especially his forelegs and head.
Miffie doesn’t seem very keen on exploring although he has made an occasional foray up the sides, and even across the roof of his abode – walking upside down on the glass. Interestingly, he always orients himself head downwards at night. Perhaps he is safer from predators that way? We have not seen him fly, although this species apparently can.
(Please note that much of the technical detail in this post comes from an article in the Fauna of New Zealand series by Ramsay (1990), which is available online here.)
New Zealand has only two species of praying mantid:
- Orthodera novazelandiae – native and endemic to New Zealand
- Miomantis caffra – introduced from South Africa
The NZ species is widespread, although it is not been reported on the West Coast of the South Island. The South African species is mainly found around Auckland (which is in the North Island).
Miffie is the New Zealand species – which are easy to identify because they have a bright blue patch on the inside of each yellow foreleg, with a darker ‘eye spot’ within that. Their body is also a different shape, with a more narrow back.
Orthodera novazelandiae lay their oothecae (egg cases) in Autumn – from about February through to April or May. The nymphs emerge as early as June or July, but more commonly around September or October.
Egg development and subsequent hatching is temperature dependent. All the nymphs from one ootheca usually hatch within 1-3 days, though it can take rather longer.
The nymphs progress through 6 stages before becoming fully adult. They mate and produce their eggs in Autumn – so now is a good time to start looking for them. Bowie and Bowie suggest they are most likely to be found “within 15o of true north on open sunny branches and tree trunks.”
Every school-aged child we have shown the mantid to has regaled us with the idea that the females eat their mate, but according to Ramsay, that is rare for this particular species.
Usually the adults die off at the onset of winter, although captive ones may live longer.
Miffie is proving a very popular pet – he seems to provoke a mixture of fascination and revulsion with his feeding technique. On the other hand, as C puts it, “finally there is some use for flies, mosquitoes and aphids”.
I’m not sure how long we will have Miffie – it mainly depends on how easy flies are to come by as the weather cools. We have had him 5 weeks so far, but If we can’t find a steady supply of food, we will have to let him go again.
Praying mantis as pets
If you want to try keeping one, there is some general information here.
Ramsay describes Orthodera novazelandiae as “wholly carnivorous” and lists the following among their potential diet: grasshoppers, cockroaches, houseflies, blow flies, wasps, butterflies, moths, spiders, various larvae. Their preference is for flies.
The quantity they eat can be large, with quite a range of quantities reported – somewhere between 1 to 6 flies daily seems to be a minimum, depending somewhat on the type (and therefore size) of fly.
If you start with nymphs rather than adults, then smaller prey like the aphids or Drosophila (fruit flies) are suitable.
What follows is a little more detail on our fly-catching technique – just in case anyone actually does want to know….
Catching food for a praying mantis
Fly-catching has only been successful here when it is not too cold, and most days at the moment (autumn) that means waiting until the afternoon and going to the sunny, sheltered part of our garden. We use a small fishing net for the initial capture, which we do when they land on the ground.
Once we have caught one we lift the loose part of the net up, they fly upwards (towards the light), and we slide a small clear container underneath.
Once the fly is inside the container we hold the netting taut across the top and invert the net and the container. The fly usually flies upwards again, and we can slide a lid underneath and onto the container.
To get the flies into the terrarium we slide the lid partly off with some muslin cloth loosely draped over so nothing can fly out. The container is held inside and the lid taken off, again with the muslin draped over everything.
When the fly is out of the container and in the terrarium, we slide the main lid back across.
Then there is a lot of hand-washing involved.
We have also used a simple fly trap to get the flies initially:
- Cut the top off a plastic drink bottle and pierce some small holes in the bottom of it so that it doesn’t fill up with rain water
- Put a small amount of meat in the bottom.
- Place the top part of the bottle upside down, over the bottom part, with the lid left off.
The flies follow the smell and climb in, but are usually unable to figure out how to get back out again. Of course, this kind of trap does get smelly after a while.
And a final portrait of Miffie: