The Battle of the Sexes
For examples of extreme sexual conflict in the animal world, insects are the place to look. From arms races to fatal copulation, they do it all.
Insect Arms Race
It would hardly be novel to say that males and females frequently want different things. But when it comes to insects, we’re not talking about hanging out with buddies at a football game versus staying home watching romantic movies. No, this is a story about sex, and so it’s ultimately about evolution, with males wanting one evolutionary outcome and females another. Nature has set up some species for sexual conflict that goes far beyond the battle over who takes out the garbage. Take, for example, the water strider. This group of insects is locked in a sexual struggle that has all the features of an evolutionary arms race, complete with occasional detente and the threat of mutually assured destruction.
You would probably recognize water striders if you saw them. They’re found all over the world, and according to Dr. Locke Rowe, an evolutionary biologist at the University of Toronto, just about anywhere there’s a pool of water there will be water striders. As their name suggests, they’re able to walk across the surface of the water, standing on the ends of their long legs.
Their sexual conflict arises out of the different desires of the males and females. The males want as many matings as possible. The more they mate, the more babies are their kin, and the more genes they’ll pass on. For the females, though, mating is much more costly, since it takes a lot of energy to produce eggs. As soon as a female’s eggs are fertilized, she doesn’t need to mate again, but the males are still going to show interest. Also, as Dr. Rowe says, “The females actually carry the males during mating, and that’s an energetic cost. So they fight. If you see water striders on the surface and look closely, you’ll see, after some time, males jumping on females and females struggling and somersaulting to get rid of them.”
So, the females have come up with ways to try and keep the males off their backs once they have already mated. In some species they have developed long spines that make it difficult for the males to climb on them. The males have fought back by evolving their entire body into one big grappling device. Each of their three pairs of legs has grappling hooks and spines that allow them to hang on, for dear life, to the females. In one species, the males have evolved antennae that are, Dr. Rowe says, “big, muscularized, swollen-up armaments that they use for grasping those females.” These antennae are not much use for sensing the environment any more (their original purpose) – but very helpful when the female doesn’t want to co-operate.
This back-and-forth retaliation has been going on throughout the water striders’ evolution. The females develop a way of repelling males, and the males come up with a way of countering the new apparatus. Then the female comes up with a new defence, and the male responds. And so on. Except, not always. Dr. Rowe has observed that sometimes there’s a de-escalation in the arms race, and there are fewer and fewer armaments on successive generations of the insects. Depending on the particular species, the arms race seems to be raging, quieting down, or staying steady. Curiously, as long as there’s a balance between the two sexes’ armaments, all these different species are about equally successful at reproducing. That’s a lot like a human arms race. As long as everyone’s in the same boat, then how well armed you are isn’t the point; it’s the balance that counts.
Sometimes the balance is off, and whenever the male has the advantage, mating rates shoot up to as much as ten times what they are in other strider species. But that puts females under a great deal of pressure to evolve defences, so it isn’t long before they do and balance is restored. This explains how escalation can happen, but why there’s de-escalation is more complicated.
No one knows for sure, but Dr. Rowe thinks it’s because of the heavy costs of the arms race to the individual insects. Their armaments take a lot of energy to grow and maintain and can get in the way of normal activity. So, if they are not needed, might as well get rid of them. De-escalation happens when females are so far behind the males in the arms race that they just give up. Then the males don’t need to be so heavily armoured, and the ones who waste less energy building grappling hooks have the advantage, and so gradually both sexes scale back. Same thing when males are scarce; then the females’ desire to breed leads them over a few generations to abandon their weapons and be nice to the guys.
But whether it’s a full-scale war or just a skirmish, as long as the armaments on both sides are balanced, then this arms race helps the species keep striding along.
It’s pretty safe to say that men and women generally have different priorities when it comes to sex. But that isn’t just a human trait. Throughout the animal kingdom, what females want is not always matched by male desire. A good example is the humble bean weevil (Callosobruchus maculatus
), an animal that seems to have taken the battle of the sexes to a new extreme. Their copulatory conflict was first described by Dr. Helen Crudgington, a researcher at the University of Sheffield in England.
Looking for sexual activity among bean weevils is no simple task. The beetles are a common pest species found throughout the world, but they’re really small, only about three and a half millimetres long (about an eighth of an inch). And they’re fairly nondescript brown bugs, or they appear to be until you look at the males really closely. Examine the penis of a bean weevil and you’ll discover it’s covered in hard, sharp spines. The purpose of these spines? Well, when a male bean weevil mates, these spines puncture the lining of the female’s genital tract.
This is not, to say the least, what a female is looking for in a sexual encounter. So, she’s faced with a problem. She does need to get fertilized. After all, as Dr. Crudgington explains it, “It may not be in the interests of females to go along with those matings, but they obviously need at least one to get sperm to fertilize their eggs. And in evolutionary terms, it’s no good if you remain a virgin.” But the damage caused by the males, says Dr. Crudgington, “can produce costs for the female in terms of dehydration – that is, losing moisture from these wounds. And they can also be costly in the sense that they can be a route for the entrance of harmful pathogenic organisms. So, obviously, this is not ideal for the females.” Now there’s an understatement.
From the male perspective, however, there are two possible advantages to damaging the female like this. First of all, if she is injured, she’s unlikely to try to mate again until she’s healed. In the meantime, her eggs will mature, and the male who has fertilized her gets to be the father of all the offspring. Second, these wounds are so traumatic that they can leave the female close to death, and the biological response to that is to produce a lot of eggs quickly. It could be her last chance to have offspring, so, from an evolutionary perspective, she wants to have as many as possible, as soon as possible. And the male who got to her first is the one whose sperm she’s going to use when she lays those eggs. But it’s not in the male’s best interests to do too much damage to the female. Killing her is no good – she won’t produce any offspring that way, and he’ll have wasted all that energy chasing her down. For the male bean weevil, there has to be some level of restraint.
So we end up with a system that requires a certain balance. The male wants to mate with, but not damage too much, as many females as possible. The females want to mate with as few males as they can. How this manifests is quite curious. It’s what got Dr. Crudgington to look at the bean weevil’s sexual practices in the first place. She had noticed that, during mating, the females furiously kick at the males to get them off their backs. This “mate kicking,” as Dr. Crudgington calls it, is quite awkward, since the spines on the penis are lodged inside the females. But it seems to work. The females minimize their injuries, the males unload their sperm, and the species is thriving.
There’s an evolutionary lesson in all this, though. It doesn’t seem to make evolutionary sense for a species if sex is this dangerous for the individuals involved. It can only reduce the number of potential offspring. But evolution doesn’t work at the level of species. It’s the pressure on the individual to do the best he or she can for himself or herself that results in evolutionary change. And these spiny penises are great for the males, so they’ve stuck around (so to speak).
The Power of One
Some stories are not for the squeamish, and this one might leave you on edge. So, take a deep breath before you read on.
There’s a spider, Tidarren sisyphoides
, that has an unusual sexual habit. While getting ready to find a female and mate, the male rips off one of his two sex organs and casts it aside. Then, unencumbered by the weight of the organ, he heads off in pursuit of a paramour. This seems like an odd and extremely painful measure, but Dr. Duncan Irschick, now a behavioural ecologist at the University of Massachusetts, Amherst, thinks he knows why self-mutilation is this spider’s best strategy.
The answer comes from the evolutionary history of this critter. As is the case with many species of spider, the female T. sisyphoides
is much larger than the male. In fact, in this species, the difference is huge: the female is one hundred times larger. And, not to put too fine a point on it, her sex organs are proportional to her body size. That’s a real problem for the male. If he’s one hundred times smaller than his mate, and his sex organs – or pedipalps, as they’re called – are proportional to his body, he’s never going to match up with his partner. What’s he to do? The answer is to develop really big pedipalps.
Calling them “really big” is an understatement. The two pedipalps each make up about 10 per cent of the spider’s total body mass. Dr. Irschick describes them as “giant beach balls sitting in front of the male.” They are big enough to fertilize the female, but they come at a cost for the males. They’re so large that when the male starts to walk or run, they drag along.
The male spiders want to find the females as quickly as possible. After all, as Dr. Irschick says, “Whichever male in this species finds the female first gets all the goodies.” If you want to speed yourself up, as any car enthusiast knows, one way is to reduce drag. So, these male spiders spin a silk thread (they are spiders, after all), wrap it around one of their pedipalps, tighten the thread to seal it off, suck out the fluid, and, well, rip off the unnecessary organ. Don’t try this at home! Also, as Dr. Irschick discovered, humans shouldn’t do this to the spider – he won’t survive. But when the male performs the surgery on himself, he’s able to head off quickly in search of a mate.
Removing this organ makes a major difference. In Dr. Irschick’s lab (he was working at Tulane University at the time), the researchers chased spiders, some with one and some with two pedipalps, around a track, to see how long they’d last. On average, the “intact” males pooped out after sixteen minutes, while the single-sided spiders lasted for as long as twenty-eight. Putting it in human terms, Dr. Irschick says, “That’s the equivalent of you going out and running about 2 miles [3.2 kilometres] versus ripping off your reproductive organ, or leg or some appendage, and then going out and running 3.5 miles [5.6 kilometres]. It’s a big performance advantage.”
The males definitely need this advantage. Female spiders of this species are few and far between in the forests of the southern United States, where they live. So males have a real challenge finding them. Any benefit in speed that they can get for their hunt is going to be critical. Of course, this advantage might come at a cost, too. It’s possible that losing one pedipalp cuts down on the amount of sperm the male can produce. But as far as anyone can tell, the males seem to be doing all right so far – the species’ population isn’t in any trouble. And while it might be painful for the spiders, until someone comes up with a way to conduct spider questionnaires, we’ll never know for sure whether it is.
If you think that the male has already sacrificed enough for the sake of sex, think again. For the male of this spider species, mating is basically a suicide mission. After he finds a female, they copulate and he stays attached to her body, which probably blocks access for other males. Eventually he dies, at which point, Dr. Irschick says, “He basically gets sucked dry [by the female] and flicked off like a piece of dirt, afterwards.” This is not exactly a great future for a young male spider to look forward to, but at least his genes are transferred to the next generation.
There’s one question that remains in this tale of self-sacrifice. Wouldn’t it be much easier for the male to evolve a larger body, to mate more easily with the female and keep his organs from dragging? The problem is, the bigger the individual male, the more energy he needs to expend finding a female. So, in fact, being small is an evolutionary advantage to these males. For the females, however, bigger is better, since the larger she is, the more eggs she can produce. So, the organ removal by the males seems to be a compromise solution. The alternative of evolving a single pedipalp is probably too difficult, because biology prefers symmetry. And ripping one off is a quick, easy operation, and it gets the job done.
But it does make you wonder: what possessed the first male spider to try tearing off a part of himself?
Bedbug Penis Tasting
Bedbugs are not a particularly romantic lot. For the males, sex is wham, bam, thank you ma’am
. The females, on the other hand, are a deceptive bunch, each trying to appear chaste, even virginal, in their attempt to attract the male with the most sperm. But male bedbugs have their own means of testing a lady’s virtue. They’ve developed a phallus that can detect whether a female they’ve mated with has been faithful. Dr. Michael Siva-Jothy, an evolutionary physiologist at the University of Sheffield in England, thinks that this is an adaptation that prevents the males from wasting sperm.
Before we get to the perceptive penis, here are some other interesting facts about bedbug sex that are worth knowing. First, even though the females have a fully developed reproductive tract, the males don’t use it. It’s strictly for laying eggs. Dr. Siva-Jothy explains this oddity: “The male’s penis is like a hypodermic needle. He stabs it into the body wall of the female, and he inseminates directly into her body cavity. Now, that’s pretty strange.” Pretty strange, indeed. The sperm migrate into the female’s bloodstream and swim to the ovaries, where they fertilize the eggs.
This isn’t some kind of evolutionary mistake. Nor do the males just have really bad aim. In fact, while the male bedbugs of primitive species will stab females anywhere in the abdomen, Dr. Siva-Jothy says that in the more evolved species “the females have little grooves and channels in their cuticular armour, which guide the male to one particular spot.” This spot covers an organ, unique to bedbugs, that stores immune cells which protect the female from infection. This is a pretty important defence for her, since she has to put up with being stabbed by any interested males.
This is where the sensing penis comes into the picture. Dr. Siva-Jothy noticed that when females mate with more than one male (not an uncommon occurrence in the bedbug world), the first male copulates for longer, and deposits more sperm than the males who come along later. In fact, the last male to stab her would be the fastest at it and leave the least amount of sperm. Since the only part of the male bedbug that comes into direct contact with the female is the penis, it set Dr. Siva-Jothy to wondering if there was something special about this organ that was allowing the male to tell whether the female was a first-timer or not.
Interestingly, a look at a bedbug’s penis under an electron microscope reveals that it’s covered in tiny, fine bumps, which in other insects are associated with chemical receptors – or, as we think of them, taste buds. It turns out that a bedbug’s penis is capable of tasting the female’s abdomen.
To test whether this was indeed what was going on, Dr. Siva-Jothy painted the penises of some virgin male bedbugs with sperm from other males and let them breed with virgin females. (And if you want to know how to paint the penis of a bedbug, Dr. Siva-Jothy’s says, “With a paintbrush.”) Sure enough, the males with the sperm-painted penises spent less time mating, and deposited less sperm, than the males whose penis had been painted with salt water. They were “tasting” or sensing the alien sperm on their penis and surmising that another male had got to the female first, even though these females still had their virtue intact.
Why would they do this? While the answer isn’t completely clear, it most likely has to do with sperm competition. All the males who mate with one female want their sperm to fertilize her eggs. But it appears that when the first male mounts, most of his sperm are absorbed by her defensive cells. Males who arrive later don’t need to deposit as many sperm, as the cells are all full of the first male’s sperm and his can get past and carry on their journey. In fact, the last male has about a 68 per cent advantage over his earlier rivals. His sperm will fertilize 68 per cent of the eggs, even though he supplies the least amount. And he’s got sperm left over for another mating with another female.
The advantage to the females of this weird way of mating isn’t at all clear. But if they’re going to get attacked during sex, at least they’ve found some small way to protect themselves. It’s sexual competition at its most fierce!
Fishing Spider Sex
The femme fatale
was a staple of classic Hollywood movies even before Barbara Stanwyck used her charms on a hapless insurance salesman to shocking effect in Double Indemnity
. And the men in those movies never learn. The allure of sexual danger is just too much for them to resist. But even Hollywood’s greatest maneaters have nothing on nature’s most dangerous vamp, the female fishing spider (Dolomedes triton
). These females are so ferocious that when they invite a male for dinner, he often ends up as the appetizer. That’s what Dr. Chad Johnson, a researcher at Arizona State University, has found, and he thinks he knows why males sometimes end up as dinner, and sometimes as a date.
Fishing spiders are found in lakes and ponds throughout eastern North America, as well as in Central and South America. Like the water striders that most people have seen, these critters can run on the surface of water, but they can also dive underneath it. Yet they spend most of their time at the water’s edge, anchored to a plant, where they wait for vibrations on the surface. When they feel a ripple through special sensors on their legs, they pounce, capturing whatever hapless insect – be it grasshopper, cricket, or damsel fly (or leaf or twig) – has alighted nearby.
This is fascinating behaviour, but, of course, what really interests us is how males and females copulate. In many spider species, the male takes a risk when he mates. After the deed is done, it’s not unusual for him to be eaten by the female. But Dr. Johnson has noticed something different in this species. “Fishing spiders are known for their voracity,” he says, “in that females will attack courting males before the male has even mounted the female. Females will take a lunge at him.” Dr. Johnson describes this as a “conundrum” for the spiders. Obviously, males aren’t getting anything out of the interaction if they’re ending up as food before they’ve had a chance to mate. But then, the females aren’t getting anything other than a meal either. They are not getting their eggs fertilized. And the species isn’t going to survive for very long if they eat every male that comes along. The female has to have some means of selecting when to eat males and when not to. That’s what Dr. Johnson wanted to figure out.
The first idea he tested was something called the “adaptive foraging hypothesis,” he says. “That’s a very intuitive idea that sometimes food might be more important to the female than sperm. If that’s the case, then the females might benefit more by eating the male than by mating with him.” Of course, this doesn’t explain why the female wouldn’t try to do both, mate then eat, but it could be that food is the more pressing need for the female at the time.
The hypothesis didn’t hold up. “Hungry females,” Dr. Johnson says, “do not try to attack males more often than well-fed females, and that would be an underlying assumption of this adaptive foraging hypothesis.” Hungry or not, the females’ desire to chomp on males didn’t change. Which led Dr. Johnson to turn the hypothesis on its head.
The flip side of the idea about food availability is male availability. If females sense that there are plenty of males around, then sacrificing one or two for food might not be such a bad thing. Another one will come along soon enough, and when she’s ready to mate, he’ll be by. On the other hand, if there are few males out there, then it’s better to mate first and eat later, just in case she never sees another male. Knowing how many males are around, then, becomes key.
There’s some evidence that this might be happening for fishing spiders in the wild. Male fishing spiders mature before the females and will move into an area where a female lives and try cohabiting with her until she matures. Dr. Johnson says, “This is usually two or three weeks, in which he’s living two or three cattails over. They can smell each other; they can hear each other’s vibrations on the water. He doesn’t get too close because she’s cannibalistic at this stage as well, but he does give the female some experience of his presence. I’ve even found females in the field cohabiting with two or three males.” All this suggests that young females might know whether they’re in a good place for finding males.
Dr. Johnson tested this idea out in the lab (he was working at the time at the University of Toronto, Scarborough, with Dr. Maydianne Andrade, whom you’ll meet in the next story). “I housed some females with cohabiting males,” he says, “and I housed other females with controlled females – this is, another spider that won’t give them the pheromonal, or chemical cue. So the prediction was that females housed with males would obtain an experience of future mate availability and they would actually be more likely to attack males upon adulthood than females that were housed with another female.” And that’s exactly what he found. The females housed with males were much more likely to eat males before sex when they were adults, showing that it’s a judgment they make based on earlier experience. Lots of males around, then she might as well eat a few before settling down to mate.
Unfortunately for the males, they have very little control over this. The females are larger than they are, by up to one third. So the males, who want to breed, have to take this risk. Sometimes they get lucky, other times they just end up as lunch. In this species, familiarity, when young, doesn’t breed contempt – it breeds an appetite.
Redback Spider Sex
Humans, for the most part, have transformed the sex act from a mere biological necessity into something playful and pleasurable that’s now usually not about reproduction. We aren’t the only creatures to do this, but for many other species, sex is a deadly serious activity. Literally deadly, in some cases. For instance, we know that many male spiders get eaten by the female after mating. It’s what biologists call sexual cannibalism. And there’s one species, known as the redback spider (Latrodectus hasselti
), that’s added a particularly brutal twist to their mating ritual. For them, sex and sustenance are tightly intertwined, as Dr. Maydianne Andrade, an evolutionary biologist at the University of Toronto, Scarborough, has discovered.
Redback spiders are native to Australia, and they look a lot like their North American cousin, the black widow. The main difference is the red stripe, missing on the black widow, but present on the back of the redback. Females of this species are one centimetre long (a third of an inch, or about the size of a marble); males are much smaller, at about three to four millimetres long (something like a seventh of an inch, or the size of a grain of rice). Don’t step on one of these if you see them. Like the black widow, the redback is a poisonous character.
You’ve probably heard of the black widow, and even its name suggests that the female eats the male after sex. But in the redback spider, the female doesn’t need to work nearly as hard to get her post-sex meal. “Instead,” says Dr. Andrade, “males of this species actually twist their body onto the female’s fangs while they’re copulating. Because of their unique anatomy, the female can eat the male while they’re copulating.” That’s right, the males not only allow themselves to get eaten by the females, they encourage it. Why? you ask. It turns out that being eaten alive gives a male a mating advantage.
For reasons that aren’t yet clear, the mating lasts longer when the female is eating at the same time. The longer copulation lasts, the better it is for the male in two ways. First, the longer sex lasts, the more eggs he can fertilize; and second, if he mates long enough, then he can place a plug in the female’s reproductive tract. That sounds harmless enough, except for one thing: the plug is a part of his own body. “That’s where it gets even more gruesome,” says Dr. Andrade. “Males of this species actually break off a piece of their copulatory organ and deposit it inside the female’s genitalia.” Why put in a plug? Quite simply, it prevents any other male from depositing his sperm in the female. Which is one way of ensuring your genes are the ones that get passed on to the next generation.
But the story doesn’t end there. Female redbacks store the sperm in two separate sacs. This ups the ante for the male, as he wants to fill both sacs. This means he’s got to go through the whole mating sequence twice. Luckily, even though he’s already broken off one of his copulatory organs, known as palps, he’s got a second one, and her reproductive tract is only partially blocked by his first palp. So, says Dr. Andrade, “He copulates with one and he’s actually standing on the female while he’s doing this. He then climbs off the female and courts her again, climbs back on and inserts his other copulatory organ.”
Remarkably, the male spider goes at it the second time already partially eaten. The female was chewing away on the male during the first round, and continues to eat him for the second round. Because the male needs to survive long enough to get to the second copulation, he’s evolved to make this possible, but it isn’t pretty.
Once copulation starts, the male, whose abdomen looks like a swollen grain of rice when sex begins, contracts around the middle, as if tightening a belt. The female chews on one end, and it looks as if the male has forced all his organs to the other. She gets a meal, but he gets to survive. Dr. Andrade says, “When he does this, even though the female is biting into him and blood is bubbling out, he’s able to court her again. In our experiments, we found that he could survive long enough to run around in an endurance test we did, long enough to court again, and long enough to mate again.”
The males certainly do their best to survive as long as possible. But, alas, after the second mating, that’s it. Not only has the female had time to chew all the way down to his internal organs, but the male has run out of sperm, so he has no incentive to keep going. That’s another key point of spider biology. Mammals produce sperm in the same set of tubes used to deliver them, but in spiders these two functions are separate. Male spiders produce sperm in a gland on their abdomen, then they deposit it on their web, and collect and store it in one of their palps. That means that even if the males survived the second mating, they’d have to go through the whole sperm manufacturing process before they could mate again, which, considering the damage they’ve received, would be unlikely to succeed.
Still, the question remains, why go through such a dramatic process to mate? This is a one-shot approach for the males, and if it fails, their genes never get passed on. The answer is that up to 90 per cent of males never find a female to mate with. The odds of finding a second female are so low that the males are better off throwing everything they’ve got at one mating, rather than trying to find more females.
And if you’re only going to get to have sex once in your life (if you’re a redback spider), you’ll go to any lengths to make sure it works, no matter how fatal that might be.
This suicidal behaviour isn’t the only odd thing about the male redback spider. He is also much smaller than the female, by as much as forty times, yet being small doesn’t give him an advantage over larger rivals – quite the contrary. This fact puzzled Dr. Michael Kasumovic (who is now at the University of New South Wales in Australia, but was one of Dr. Andrade’s graduate students at the University of Toronto, Scarborough). He found that when small and large males were placed side by side to approach females, the larger males would always beat out the smaller ones. They would just push them out of the way. Yet, in the wild, small males continue to exist.
The key seems to come out of the cues that cause smaller males to develop in the first place. And the word “develop” is important here. Earlier work by Dr. Kasumovic and his colleagues had shown that it’s not genetics that leads to smaller males. Rather, when the males could sense, somehow, that there were lots of females around, but not too many males, then they sped up their own development and hatched, on average, a day sooner, when they were still small. When there were more males than females, then the spiders wouldn’t hatch until later, when they were larger.
To see if this led to an advantage for the early-emerging spiders, Dr. Kasumovic set up two different conditions. In one, three large and three small males were all released together to find females. As expected, the big males beat out the smaller ones. But if the small males were released a day ahead, as would happen in the wild, then they got to the females first.
Dr. Kasumovic explains, “When there are a number of males all searching for the same female, and they arrive at the female at the same time, there is going to be a benefit of larger size. When there are more males around, it’s better for him to take a little bit longer to develop, to make sure that he’s a little bit bigger than the average size. So he can actually compete and out-compete these other rival males when he does reach a female’s web.” But if there are lots of females and fewer males, he’s better off rushing to get there first.
It’s a curious balance. There are advantages to both approaches, and, depending on the details of the season, each one has a chance of winning. Which just goes to show you: sometimes, size isn’t everything.
Some Crickets Like it Rough
The cricket equivalent of dinner and a movie before a first kiss is the song the male produces by vibrating his wings. Female crickets like to be serenaded before letting a male mate with them. But according to Dr. Karim Vahed, from the University of Derby in England, there’s one species, the alpine bush cricket (Anonconotus alpinus
), whose males are so virile that they don’t bother with such formalities.
If you want to see the alpine bush cricket in action, you’ll need to head to the French Alps. There, you’ll be looking for a brown, plump cricket, about two and a half centimetres (one inch) long. Other than their size, they look like any other cricket.
What’s special about them is their mating behaviour. We’ve all heard crickets call – it’s one of the quintessential sounds of a summer night. The males are advertising their position; the females are attracted to the male, they climb on, and mating ensues. As Dr. Vahed puts it, “The females are on top in the cricket world and copulation occurs.” But not for the alpine bush cricket. In this species, the males search through the long grass of the alpine meadows, and when they come across a female, says Dr. Vahed, “they leap on her without any prior warning, wrestle her to the ground, and use a large pair of pincers at the end of their abdomen to maintain a vice-like grip while they begin copulation.”
If that wasn’t enough, these males are so highly sexed that just eighteen seconds after they’ve finished mating they’re ready to jump on another female. Or, indeed, on any other cricket that’s around. They are extremely indiscriminate when it comes to mating and will jump on the back of any cricket that’s close by, male or female, young or old. This eighteen-second turnaround is remarkable – the males of other cricket species can take as long as five days to recover and be ready to mate again.
However, there has to be a limit to how many times they mate, or, as Dr. Vahed says, their lives would be “short but happy.” In captivity, he’s seen males mate as many as seven times in quick succession, and he’d like to study some males in the field to see if they also mate this frequently and rapidly.
That’s the male’s side of the story, but there’s another player here, the female. She comes off the worse for this encounter. Dr. Vahed says, “When you collect females from the field, you’ll find that most females have distinct bruising on their abdomen in the region that’s first gripped by the male’s pincers.” Which makes you wonder, why doesn’t she resist? The truth is, she does. When mounted, Dr. Vahed says, the female “kicks and bites at the male, and also they have a technique of walking quickly through vegetation to try and brush the male off. In most of these cases, when the female does choose to resist, she actually succeeds in dislodging the male.” One theory is that by resisting the male, the female is ensuring that only the strongest, and therefore healthiest crickets are getting to pass on their genes. Only the best of the males get away with the rough behaviour.
As weird as this behaviour is, there’s one more fact that just adds to the strange story. These silent males are perfectly capable of chirping. In the lab, Dr. Vahed has isolated males and found that after eighteen days or so, they’ll revert to calling for females. Which suggests that there are two different strategies this species can use. When there are plenty of females around, the males just sneak around and jump on unsuspecting females. But when the females are few and far between, it pays to advertise.
Of course, if any male’s approach is to sneak up on females, it doesn’t make sense to sing. Stealth may be what explains their silence.
Excerpted from Nasty, Brutish, and Short by Pat Senson. Copyright © 2010 by Pat Senson. Excerpted by permission of McClelland & Stewart, a division of Random House LLC. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.