It may just be because I've just been to see the new Predators film (No Arnie, no point in my opinion) but their heads to bear a striking resemblance to the dreadlocked death-machines from the film. Couple that with a slender, spiky body that could be out of Aliens and they're a sci-fi nerd's dream bug.
It's not just in appearance that these guys seem like aliens, their behaviour is pretty strange too. Unlike other predatory bugs such as many arachnids, ants or centipedes, mantisesrely on sight as their primary sense used for hunting.They are great at seeing movement, like many insects, but also and have a "sweet-spot" or fovea that can resolve detail at a distance of potentially up to 50 feet. Although this is not that remarkable in human terms, for an invertebrate, particularly one with compound eyes it is unusually good.
They have good depth perception too, and will sometimes sway like sick insects do to improve this by using parallax, before hitting out with their strong and spiky forearms. Their use of crypsis is like stick insects too, their colouration and shape enables them to blend perfectly into their background and stalk their prey. The cricket doesn't stand a chance, and is eaten while still nominally alive. Twitching at least. You can actually see that the antenna are moving in this picture, and while insects do not have a nervous system like us or pain receptors like mammals and other vertebrates do, you've still got to feel a bit sorry for the thing. That is not to say that other predators like spiders are in some way morally better for killing their prey a bit quicker. Predators kill their prey in a quick and efficient way to protect themselves, not spare the prey's suffering. Imposing human ideas like suffering, morality and pity is anthropomorphism (something I wrote an entire dissertation on) and although these are natural human responses to this issue, they are not scientifically appropriate. How and why prey are killed are interesting scientific questions, but anthropomorphism obscures the science if not used carefully. For a mantis, there is no need to ensure a prey item is dead because there is no escape from it's vice-like grip. For a spider, venom is required to eat because of its mouthparts.
Female mantises are notorious for eating males during or after copulation, which when seen from a human perspective seems horrific. Considered through the eyes of natural selection, however, this must be a successful strategy for mantises. Male mantises provide only genetic material for the next generation, making no further contribution to their offspring. Females that eat their partners get more food than those that do not, so are better nourished to provide a ootheca (egg sac) for the several hundred baby mantises to grow inside. If fact, it could be said that being eaten is the male's contribution to this next generation. Of course, males that can escape their hungry partner can then go and find another females to mate with and so may produce many thousands for fertile eggs, but these females may be under-nourished and so the eggs never survive to reproduce themselves. This is the essence of natural selection; anything genetically based (which can include behaviour) that improves the chances of the next generation's survival will flourish. Female mantises tend to be larger and stronger than the males and so can, if hungry, eat them. Male mantises are also able to continue copulation whilst being eaten (as I said before, their nervous systems are very different from ours). Both behaviours help the survival of the next generation, regardless of how we may regard to view them as humans. Of course, this behaviour would not work in animals that require more parental care from both parents, as is the case in most vertebrates, but it does go to show that nature is not nice, or nasty.
Still, natural selection rants aside, despite being highly successful predators, mantises are prey for many larger species such as mammals and birds. The latin species name of the Peacock mantis, pinnapavonis, literally means "peacock tail", because of peacock-like eye spots on the adults wings that are used as a threat display. T
his little juvenile is too young for that at the moment, but if faced with danger (in this case being threatened with a biro) they will hop around then collapse on the floor and play dead. Rather than apparent death, or thanatosis, which is found in animals like opossums and some snakes, this is more likely a use of their crypsis as the brown colouration of the body makes them hard to spot. Thanatosis relies more on predators preference for live prey to put them off, although some scientists do consider it a form of crypsis. It seems that the playing dead behaviour may be more common in males, so I think the mantis may be a he. He is as yet unnamed though, so name suggestions in the comment box please!
Facebook has named the mantis: Filthy Lucre the Sardinian Diamond Thief.
ReplyDelete