I read a little about mantis shrimps while
taking invertebrate zoology and had even seen a couple of
T.V. shows that featured them years ago. I thought they were
neat little beasties to say the least, but admittedly I never
paid too much attention to them in the subsequent years. When
perusing general literature on the subject, what I invariably
picked out was that they hide a lot, they can be very aggressive,
they cannot be trusted with other "meaty" invertebrates
or small fishes, and they can even be dangerous. In addition,
I very rarely saw them in stores, and never knew anyone personally
that had one (that they wanted), either. So, as much as I
like cool critters, I never felt the need to buy one and bring
home yet another pet that might need it's own tank.
But, as I was shopping in Tampa one day,
looking for something interesting to put in a 20 gallon tank
that I'd recently set up, I happened to come across a tiny,
bright green mantis called Neogonodactylus wennerae.
The aquarium didn't have too much in it really, so with a
rather spontaneous change of heart, I figured I'd go ahead
and give one a try. It was only a few dollars and a small
local species, so I figured if I didn't like it I'd just let
The story of how things went after that
will come in a minute. But first, some information about mantis
shrimps in general. Some information on how to care for them
- or how to get rid of them follows, as well.
General Biology Stuff:
There are somewhere in the neighborhood
of 450 species of mantis shrimps, being a diverse bunch that
range in adult size from less than an inch up to almost 16
inches, with the majority being between 1.5 to 4 inches. They
are found worldwide in temperate and tropical seas, and all
are placed in the Order Stomatopoda, which is part of the
Phylum Arthropoda. While they're called mantis shrimps, the
odd thing is that they aren't really shrimps by definition,
or mantises either for that matter, and they are properly
called stomatopods. But, they certainly look enough like a
cross between the two for the common name to stick whether
it's "correct" or not.
They aren't "true" shrimps for
a number of reasons, with the most obvious being their possession
of specialized prey-capturing/killing limbs known as raptorial
appendages. These raptorial appendages are found where we
would normally expect to see some sort of pincers on a true
shrimp or crab, and are quite multi-purpose, being used for
predation and self-defense, and often for modifying their
environment when necessary, as well. There are also two discrete
and different forms for these appendages, leading to a division
of all mantises into two large groups. Depending on which
form they brandish, mantises will use them primarily to break
things, or to stab things. Thus, they are called either "smashers"
or "spearers," respectively.
There are some general behavioral differences
between the two groups, too. Smashers tend to live in holes/tubes
in rocks, or rock rubble, but spend time roaming about stalking
prey. They tend to feed on crabs, snails, and other shelled
victims, and will use their "weapons" to pound open
their victims' shells, eating the contents afterwards. Conversely,
spearers tend to build and wait in burrows on soft sediment
bottoms, and feed on fishes and other soft-bodied prey using
an ambush technique. They stay in place and wait for a victim
to inadvertently come into their range, quickly reaching out
to nail them. One type of mantis may eat the other's preferred
food, though, if the need and opportunity arise.
Other than the fancy weaponry, they also
consistently have a shortened body and an elongated, very
flexible tail, which allows them to turn around quickly and
easily in tight spaces and in burrows. The tail and the specialized
oar-like swimming appendages on its underside also allow the
shrimps to scoot/swim surprisingly fast when on the hunt,
or when they get spooked. They also have some serious vision
equipment, having extraordinarily advanced eyes on short,
but highly mobile stalks. This allows them see extremely well
and look in different directions simultaneously, too. And,
they provide exceptionally accurate depth perception (target
acquisition), making their lightning-quick weapons that much
more effective and deadly.
The Weapons in Particular:
Check out the pictures. Taking a close
look at one of the raptorial appendages will reveal that it
is comprised of three main segments, which can be folded up
very tightly when not in use. As you can see, the last segment
of the weapon also looks quite different depending on whether
it belongs to a smasher or spearer.
The smasher's has a very sharp, single
point at the end of the last segment, which can be used like
a knife to stab or slash at soft tissues. However, it's the
base of the segment that has a thickened heel that is used
for bashing things. When using this heel, the last segment
is kept in the folded position (as shown), with the pointed
tip tucked in. Thus, they easily can handle soft and hard
targets as needed.
are shots of a N. wennerae's smashing appendage,
with the last segment folded in place for bashing. Note
the sharp point, but lack of spines, and the flattened
heel at its base. It's hard to believe something so
small can be so effective.
Conversely, the spearer's weapon can have
something like 3 to 17 upward/outward projecting spines on
the last segment, but no heel at it's base. The spines are
used to impale victims in a Freddy Krueger fashion, and are
then flipped back towards the second segment to hold the prey
in place for eating. They work essentially the same way an
insect Preying mantis' weapons do, but in the opposite direction.
They fold up instead of down.
beautiful weapons. Look at this thing! These are two
shots of O. oratoria's spearing appendage. One
in the "tucked" position and the other partially
I read the same thing in three or four
different places (although it was never specifically referenced),
"... they can strike at 10 meters per second...one of
the fastest movements in nature..." But, at first glance
that didn't sound very fast to me, really. So, I was a bit
confused for a minute. After all, I can run almost that fast
(well, maybe 15 years ago I almost could). Anyway,
that's "only" 22.4 m.p.h. Time to use the calculator
a little more to put things into better perspective.
A little finger poking revealed that if
you're a small mantis, and only reaching out about one inch
to strike your meal - your weapon can make contact in something
like 0.0025 seconds. The victim is alive at t = 0" and
dead at t + 0.0025". Twenty-five ten-thousandths of a
second (1/400th) in between. Yeah, I reckon that is pretty
quick. A lot quicker than I can move my fingers anyway (foreshadowing).
With this in mind, while the weapons aren't
that big relative to the size of the bearer, this speed is
why they end up being deadly in the way a small, but high-velocity
bullet can be. Speaking of bullets, on one show I saw about
mantises, some guys were getting a big smasher to smack a
rubber bulb on the end of a plastic tube, and then measuring
the air pressure created in the tube. The resulting pressures
were actually up there with the force produced by the hit
of a small bullet. Makes me have bad dreams about stepping
too close to one and having my ankle shattered...
If they can hit this hard, it should be
no surprise that such an individual can shatter glass panes
and knock the side or bottom out of an aquarium. We're not
talking about a one-footer either, as a enraged smasher half
that size can likely bust out of anything not made of kryptonite
if it chooses. Fortunately, there are plenty of attractive
species out there that stay relatively small and shouldn't
present such problems.
A Few Other Tidbits (Random Stuff I Found Interesting):
- Many mantises will live at least four
or five years, some several times longer.
- They are well-known for having exceptional
vision. Their eyes contain 16 different types of photoreceptors,
12 of which are for color analysis, compared to three in human
eyes. This allows them to distinguish up to 100,000 colors,
compared to around 10,000 or less, seen by humans beings
(I'm partially color-blind).
- Their eyes also posses various color
filters and polarization receptors, allowing them to see polarized
light and four colors of UV light.
- They may be the only invertebrates that
can identify individuals of the same species by their
"body odor." In other words, they smell and remember
well enough that they know Bob from Bill from Jane, not just
that they are other mantises.
- They get into ritualized fights (like
rams, etc.) in which they trade licks upon the terminal flaps
of each other's flexible tail section. They can go at it,
decide a victor, and not really get hurt in the process, although,
on occasion, they will fight to the death.
- Many only get together for one-night
stands, but there are others that mate for life as a monogamous
pair, depending on the species.
- Eggs may be laid and kept in a burrow,
or they may be carried under the female's tail. Regardless,
once they hatch they may spend three months as plankton.
- Some may change color with changes in
lighting and their surroundings. For example, some specimens
from deep waters may be dark blue or reddish, but can slowly
change to bright green in a well-lit aquarium that houses
macroalgae like caulerpa. This occurs when they molt.
There's much, much more, but this is going
to run long as is...
My Own Experience with One:
My 20 gallon contained a few good pieces
of aquacultured live rock/coral rock, a sand bed, and two
fishes. There were also a few snails and hermit crabs, too.
I removed the three small Astraea snails, but left
three much larger Turbo snails in, and left the hermits
in, as well. With the exception of a relatively large spotted
hermit (Dardanus megistos), the rest were small ones
that I collected myself, and I considered the small ones "expendable"
and the big one "tough enough." The mantis was a
very little one, being in the neighborhood of only an inch
In it went, and hid. But, soon after, the
search for a home started and it found a hole of some sort
near the back side a large piece of live rock. Then it started
to jackhammer the inside of the rock and I could hear intermittent
rapid popping sounds for a couple of days, or so. A hole later
appeared on the front side of the rock, just above the level
of the sand substrate. It was a good miner. Upon inspection
with a flashlight, I found that the mantis had enlarged the
diameter of hole, as well, making it big enough to turn around
in. Afterwards, attention was turned to the opposite side
of the tank and a burrow of sorts was excavated under a couple
of other pieces of rock. All I would see was a flurry of sand
flying out from under them. Initially, it stayed in one of
the two locations about 99% of the time the lights were on,
primarily in the rock.
first this was about all I got to see: eyes looking back at
me from a hole.
Within a week all of the little hermits
were gone. No surprise. I even saw the attack once, as I happened
to eye a small object flying up from the bottom immediately
after hearing a distinctive tick, tick sound. Another smack
or two, and the hermit's shell was breached and the eating
began. Cool! Besides the small hermits, the only other things
to disappear were all of the barnacles on the live rock. Their
little forts were no match for my little smasher, and they
were all dispatched before long.
I collected more hermits, but I also started
adding dried shrimp pellets, too. It liked them. It also fancied
flake food and brine shrimp, as well. Easy to feed, albeit
a very shy diner. I was also pleased that as best as I could
tell, the mantis had made no attempts to eat the turbos or
the big hermit. In fact, I'd go so far as to say the mantis
actually ignored them, even when they were very close
It was such an interesting little critter
to watch, as it would sit in it's hole, looking all around,
slowly creeping outwards every once in a while to look around.
It seemed to eventually realize that I wasn't a threat, and
accordingly began to spend more and more time outside the
hideouts, walking about. It began to give me the distinct
impression that it was very curious, not just out looking
for a meal, and enjoyed watching me as much as I liked watching
lookin' at me?"
Here's my mantis, Neogonodactylus wennerae, striking
a pose, with head and weapons up and
ready for action. Pretty fierce for something that reaches
a maximum size of less than 2.5 inches.
Over the next several months I added more
corals, more fish, and even a skunk cleaner shrimp, with no
problems. The mantis seemed to be content with the fish foods
and occasional little hermits. But, then things went wrong.
For reasons unknown, the mantis decided to have a showdown
with the big hermit, and I happened to be there to see it.
It had almost doubled in size by this time, to around two
inches in length, and possibly decided it was now large enough
to handle the big guy.
The mantis darted out of its burrow and
smacked the hermit's shell a couple of times. It was a pretty
heavy shell though and nothing happened. The hermit just jerked
in and sat there. The mantis retreated to its lair and waited
for the hermit to come back out, then tried the same again.
Still no damage to the hermit. So, at this point I thought
maybe the mantis was just harassing the hermit and might get
tired of it and quit. Nope. The third try was a charm, as
the mantis caught the hermit before it could retreat, went
for the head, and whacked off one of its stalked eyes. Time
to break it up and save my hermit! I banged on the front pane
of the tank, the mantis split, and I yanked the hermit out
just in time.
poor hermie lost an eye in a fraction of a second. I imagine
if I hadn't been
there to break things up, it would have lost a lot more, though.
FYI, he's over
three years old now and doing fine, even with one eye.
I thought about what to do for a bit and
decided to pull the mantis out and move it elsewhere. At the
time I was also playing around with a non-coral aquarium with
lots of rocks and sand, but only a few other fishes and inverts
that I had collected, and figured I'd transfer the beastie
over. So, I sat down and made a trap.
The mantis liked brine shrimp a lot, and
would chase them around in the aquarium's currents, giving
me a good idea of what to do. It was really pretty simple.
I put some brine in a glass and covered the top with some
clear plastic-wrap, only leaving a small gap at one side open.
I positioned it near the mantis' hole and about one inch from
the side of the tank, then moved my magnetic cleaning magnet
(that's about one inch thick) in place just above the gap
I'd left in the plastic. Only slightly more ingenious than
a chimp using a stick to eat termites.
smart as it seemed, I caught it with a simple, expedient trap
in only a few seconds. Twice. You can see how the cleaning
magnet came into play if you look at the right corner of the
It literally took only a few seconds for
the mantis to get a whiff of the food and come shooting out
from it's den. It located the gap quickly and went in for
the grub, and I just as quickly came down with the magnet
to block the opening. Gotcha! I figured it would be a bad
idea to leave it in a glass container for too long though,
and had pulled out a plastic breeder/holding box before inserting
the trap. So, I grabbed the glass, poured the mantis into
the breeder box, added a piece of coral skeleton, and sank
it in the aquarium. Success! Or so I thought.
didn't look too concerned about being in the box at this point,
but that changed momentarily. When it decided to go back home,
the little devil knocked the corner out in about 10 seconds
I carried the glass to the kitchen, and
on the way back to the tank I heard the mantis pounding the
side of the box. Then, before I could even get my hand in
to grab the box, the mantis shot out of the corner and into
the rockwork. The little monster had knocked a hole in the
container just big enough to squeeze out. Got to try the trap
I was pretty irritated at this point, and
guessed that the mantis was too, so I waited a while before
repeating the same procedure. I was a bit wary of using glass
this time, though, after seeing the hole in my box and used
a clear plastic cup instead. I was actually kind of surprised
that it worked just as well the second time, almost expecting
it not to, and quickly pulled out the cup and poured the mantis
directly into the other aquarium. Sorry, but no acclimation.
The story doesn't end here though, as the
two pistol shrimp living in the tank didn't like the new company
at all. I'd forgotten about them in my haste. Pistols are
another odd sort of shrimp that has funny appendages, too.
Theirs are used to seriously stun other critters though, as
they're specially designed to make an extraordinarily loud
popping sound when closed quickly (think - pistol). Loud enough
to be heard throughout the house, and loud enough to ring
the bell of anything that bugs them, which the mantis apparently
did. Also loud enough to startle the absolute hell out of
you if you happen to have your arm in the tank doing maintenance.
Needless to say, the fireworks started
that night. Pop, pop, pop... Pop, pop, pop... Pop, pop...
like a gunfight going on. But, after an hour or so the noise
stopped and I figured they were done with each other. I assumed
the mantis had been the victor, but I was wrong again.
I got up the next morning, did some tequila
shots (just kidding), and looked in to see the mantis laid
out, in the open, with legs up, and sitting perfectly still.
Dead. Hmmmm, all that effort and it died on me (or I killed
it depending on how you look at it).
No it didn't (I didn't). I reached in to
pull out the lifeless body, only to realize that it wasn't
so lifeless. It popped a slit in my finger in less than 25/10,000ths
of a second and the blood was running fast before I could
get my hand out of the water. So, they really are thumb splitters,
or at least index finger splitters. Imagine that! There are
times when I feel like I'm real smart. There are times when
I know that I am not...
Luckily, I'd had a tetanus shot lately,
and didn't feel the need to make a hospital trip out of this.
I cleaned it up and bandaged it, and left the mantis where
it was. It never moved from where it came to rest though,
and after waiting for a while I removed it with some chopsticks.
Yes, it was really dead this time. I can't say if it was the
pistol shrimp (hard to believe) or the stress of the rapid
transfer, or both, that killed the mantis, but it was dead
nonetheless. I doubt it died of guilt.
I took a couple of pictures of the pretty
green corpse, and then pulled it apart for fish food, some
of which the big hermit ate.
stationary look. Too bad it's only possible here because it's
dead as a doornail.
On the Subject of Mantises and Food:
I moved to Japan a while back and I now
live near a small fishing marina/port. So, sometimes I enjoy
going down to the docks and picking through the catch that
comes in on the trawlers. The Japanese tend to keep essentially
everything that comes up in the nets that is animate, so I
often get to fool around with an interesting critter or two.
Fishes, shrimps, crabs, squids, octopuses, cuttlefishes, sea
cucumbers and such abound - all kept in live wells and often
still gasping when they hit the ice at the local grocery stores.
Anyway, the first time I decided to take
a look, I was surprised to find that a fisherman had a small
lot of mantis shrimp in one of his wells. As it turns out,
they're called "shako" here, and are actually quite
popular. I offered to buy some, but the fisherman gave me
a bag and seemed to be quite tickled at my excitement over
Off to the apartment I went, and soon thereafter
I began to look them over more closely. These were much larger
than mine, and much easier to handle and inspect. So, you
get to see a few pictures of these spearers (Oratosquilla
oratoria) I took at my kitchen table, and the pot that
the rest of them were cooking in while I was playing dissector.
Since then I've found that various mantises are also a popular
seafood in other parts of Southeast Asia and Italy, as well.
are the 5" food-variety mantises (O. oratoria)
seen regularly here in Japan.
While they are spearers, they must be roaming about a lot,
as quite a few come up
in fishing nets that don't dig into the bottom sediments.
is a better look at Oratosquilla oratoria, from the
top and bottom.
Aquarium Care for a Mantis:
If you decide that a mantis is the thing
for you, you have a few choices when it comes to making a
home for them and taking care of them. Putting either type
(smasher or spearer) in a reef can obviously be a bad idea
if you plan on having much of anything else that is made of
meat and moves (or doesn't in the case of barnacles). But,
I must say, my little smasher never bothered the large turbos
that I know of, or the cleaner shrimp (which was as big as
the mantis and stayed at the top of the tank most of the time
anyway), or any of the four small fishes, either. It also
never posed a threat to the corals. So, I'd think with some
appropriate stocking choices, it can be entirely possible
to keep a smaller species of mantis in a full-blown reef tank.
And, of course, either could also be kept in a non-reef tank,
as long as the fishes are big enough to fend for themselves.
barnacles aren't safe, as all of a dozen or so
in my tank were cracked in half and cleaned out.
In any case, you'll need to do as much
homework as possible (do as I say, not as I do - right?) and
will most likely want to find a smaller species to try. All
will appreciate a natural setting, including a sand bed and
some live or base rock. Many will also be quite pleased at
the addition of some appropriate diameter, well-placed PVC
pipe, and/or some big gastropod shells to call home, too.
Otherwise, a smasher will likely end up building it's own
in your rock.
As far as busting out of things goes, fortunately
the smaller species won't knock your tank apart. Especially
if they are spearers, of course. As long as they are "happy"
and don't feel threatened, they won't have any reason to do
so anyway. So, don't make them feel threatened. The "tank
busting" stories are actually very few and very far between
as best as I can tell. Sometime ago, I did read that it is
a good idea to put a piece of plexiglass on the bottom of
the tank, under the sand, which would be cheap and easy. So,
it may be worth the two dollars for a little peace of mind
if nothing else. Of course, an all acrylic tank would probably
hold up much better, too, if you're that worried about it.
When it comes to feeding, not everyone
has access to free hermits. But, fortunately most if not all
mantises will adapt to aquarium life and will take other foods.
Pieces of meaty foods are appreciated for sure, but as I pointed
out, shrimp pellets, flake food, and brine shrimp worked fine
for me, too.
Again, the key here (for the least probability
of troubles) is to do your homework on a species and then
buy it. Not the other way around. The
Lurker's Guide to Stomatopods, and the Reef Central forum
dedicated to mantis shrimps are excellent places to start.
Maybe choose an appropriate species and have someone order
it for you. You get the idea...
Aquarium Rescue from a Mantis:
For everyone else. Spearers live in burrows
in sediments, not live rock. So, it is rare for them to be
added to an aquarium unintentionally. However, smashers live
in rocks, and can often survive shipping, thus they are accidentally
added with some regularity. Then they start eating, and you
know the rest of the story. So, if you have a pest mantis
and want to get rid of it, there are numerous methods you
can try. I've obviously only used one method myself, so I
can't promise how well any of the rest of these work (or won't),
but these are what I came up with and collected from other
sources (primarily from Juan, 1998 and Delbeek & Sprung,
1994) that sound reasonable enough. There are many others
that do not...
If the evictee-to-be lives in a particular
rock, you can try the first few suggestions from the list
below. Pay attention though, as mantises often have a"back
door" exit and can scoot out of their favorite rock and
hide elsewhere, leaving you to think it must have somehow
gotten trapped in the rock and/or mysteriously evaporated.
The rest are suggestions in case you don't know where exactly
it lives, or if removing rocks just won't work for you.
- Remove the whole rock and put it in another
aquarium where the thing won't be a problem. The happy ending
- Remove the piece and put it in another
container of aquarium water, then wait for the mantis to venture
out at some point and quickly snatch the rock out and put
it back where it came from. You'll need to move fast and/or
devise some method to prevent the mantis from getting back
into the rock, though. They're speedy and wary.
- Remove the piece and pour carbonated
water into the mantis' hole. The fizzing and carbon dioxide
should drive it out (hopefully not into your lap), after which
you can put the rock back in place. Pouring boiling water
down the hole would work, too, although the mantis may get
poached in place and not come out.
- For some reason, no one mentioned removing
the piece and throwing it into the backyard. Another option...
- Simply try to spear the mantis with a
piece of wire, coat hanger, or ice pick, etc. (many sources,
- Put the intake hose from a canister filter
over the hole and see if you can suck the mantis out. Probing
the hole with a wire from the other end may help drive it
into the intake, as well. I'd make sure to be there though,
as a small but very unhappy smasher may decide to exit your
canister through the side if given the opportunity.
- Hold some scissors over the hole, use
something to bait the mantis out, or a wire to drive it out,
etc. and try to snip fast enough to cut the mantis in half
when it sticks its head out. While it worked for at least
one person, if you aren't exceptionally patient and/or quick,
I envision this technique leading to the same facial, oral,
and physiological responses that I experience after teeing
a ball into the pond three times in a row.
- Depending on what else is in the aquarium,
try adding a bird wrasse (Gomphosus varius), an Australian
dottyback (Labracinus lineatus), or an octopus. All
eat mantises, but the wrasse and octopus also eat a wide variety
of other invertebrates and small fishes and the dottyback
can be overly aggressive. So, once they've done the mercenary
work they may need to be removed themselves. Also note that
someone suggested the use of a triggerfish on a message board,
but a reply told the story of a wholesaler giving away a mantis
that had killed six triggers in a single night. I also read
somewhere about an occasion when a mantis beat the tar out
of an octopus. But, I'm sure size comes into play in such
- There are traps of sorts available for
catching unwanted critters. I have a small one called an "X-terminator"
that has a spring-loaded trap door apparatus, which might
work fine for a really small mantis. Likewise, for larger
ones, you may be able to find a suitable piece of equipment
from an aquarium supplier, or some sort of minnow/bait trap
at a fishing supply store. Just make sure to get the trap
out of the tank before the thing decides to make it's own
- Try my expedient trapping method (which
did work, as it was after the trapping when the problems started).
I'd do the same thing again as a first choice to tell the
truth, although I'd be sure to use something made out of heavy
plastic the first time, instead of glass. And again, one last
time, move quickly if this works.
- Or, maybe all you need to do is find
a big enough pistol shrimp...
you hear an unidentified popping noise coming from your
aquarium, don't panic (yet). It could be a mantis, but
it could also be a pistol shrimp. If it's a pistol,
you don't have to worry, as they are quite benign and
shouldn't cause any trouble. A mantis at work will tend
to produce several sharp ticking sounds as it smacks
rocks, but a pistol makes a really, really loud popping
sound, and usually only two or three at most at a time.
Regardless of what you try, remember to
keep your hands (fingers) to yourself!