THEY might be small, but these sex-crazed insects prove that size doesn't matter when it comes to getting down and dirty.

From bugs with eyes on their penises to critters who have nonstop sex for 79 days, it's not surprising that the tiny creatures are great at reproducing.

16 Insects are 'small, supple and sexy', so it's not surprising they're great at reproducing Credit: Alamy

A fascinating new book lays bare the bedroom antics of the little creatures, including the lazy bedbugs that penetrate their lovers' stomachs and the water boatmen that rub their own penises to 'make music'.

But it's not all fun in the world of insect sex - some critters facing injury, exploding testicles and even certain death when they engage in the activity.

Professor Anne Sverdrup-Thygeson, whose hardback, Extraordinary Insects, comes out this week, tells Sun Online that bugs have an 'immense' reproductive capability.

Her book tells the remarkable story of the insects living right under our noses - including how the 'supple and sexy' creatures date, mate, and parent their offspring.

With the exception of two - the American fish spider and the Japanese yellow swallowtail butterfly - all of these creepy-crawlies are found in Britain.

Below, we look at some of the planet's most sex-mad critters - and the incredible, bizarre and simply disturbing tactics they use to reproduce...

16 Anne Sverdrup-Thygeson says some bugs can keep having sex even with their heads chopped off

The insects who have sex for MONTHS at a time

When it comes to lasting as long as possible in bed, Indian stick insects are the champions.

The creatures, who are kept as pets in some UK homes, have apparently been known to stay glued together for 79 days in 'an extreme sport version of tantric sex'.

16 Indian stick insects can get down and dirty for 79 days in a row Credit: Alamy

Anne explains that males will make the mating process as long as possible to maximise the amount of their sperm that is delivered to the female.

She says the Southern Green Shieldbug, also found in Britain, can keep at it for 10 days.

But the male stick insects and shieldbugs 'don't transfer sperm all that time'.

16 The Southern Green Shieldbug can keep at it for 10 days Credit: Getty - Contributor

The insects who refuse to leave their lovers after sex

Anne, a professor at the Norwegian University of Life Sciences (NMBU), adds that it's quite common for male insects to 'guard' females after they've had sex.

This is so they can make sure their lover doesn't mate with anyone else.

Small blue damselflies, which can be seen in the UK, are an example of this.

16 Small blue damselflies often keep watch on their female lovers to make sure they don't mate again Credit: Getty - Contributor

The creatures are often seen perching or flying around in couples.

Anne says: "The sole purpose of this tandem position is that it allows the male to keep watch on the female and make sure she doesn't mate with any rivals until she has laid (what he hopes are) their jointly fertilised eggs on a suitable aquatic plant."



The butterflies with eyes on their penises

Insects' eyes can vary in number and type - and aren't necessarily only located on their heads.

It may seem bonkers, but the Japanese yellow swallowtail butterfly, found in Asia, has eyes on its penis.

Anne explains: "These help the male to position himself correctly during mating. The female also has eyes on her rear end, which she uses to check she is laying her eggs in the right place."

16 The Japanese yellow swallowtail butterfly has eyes on its penis Credit: Alamy

The tiny critters with the 'world's longest sperm'

You probably wouldn't guess that the record-holder for the world's longest sperm is the fruit fly - but researchers have found the tiny critter does indeed win the gold medal.

Males of the Drosophila bifurca species have tightly-coiled sperm that measures an astonishing 5.8cm when uncoiled - 20 times longer than the creatures themselves.

16 The record-holder for the world's longest sperm is the Drosophila bifurca species of fruit fly Credit: Getty - Contributor

16 The flies' sperm was found to measure nearly 6cm when uncoiled Credit: V

Anne says this would be like men having sperm the length of handball courts.

She adds that the 'long sperm are the fruit fly reproductive system's answer to Usain Bolt: the longest sperm out-compete the shorter and are more likely to win the race to fertilise an egg'.

The bedbugs who penetrate their lovers' STOMACHS

Some bug species, including bedbugs, skip foreplay and get straight to the act. And shockingly, they aren't too fussed what part of their lover they're penetrating.

Anne says they 'can't even be bothered' to find the female's genitals, so they shove their sex organ into her belly and leave the sperm to find their way to the egg cells.

16 Bedbugs skip foreplay and get straight to the act Credit: Getty - Contributor

Although the males' actions often leave their lovers injured, the females are said to have a reinforced area on their stomachs which limits their wounds.



The insects who scrape out rivals' sperm

Many male insects have a sex organ reminiscent of a 'Swiss Army knife', Anne says.

The organ comes with 'all these scrapers and spoons and other stuff', which the males use to brutally 'scrape out' any sperm left there by their rivals.

On some occasions, the females are so badly injured in the process that they can't mate again.

Males may also find their sex organ handy if a rival has deliberately 'plugged up' their love interest's genitals and formed 'a kind of homemade chastity belt'.

16 Male variable checkerspot butterflies 'plug up' their lovers' genitals Credit: Alamy

Anne writes in her book: "Male number two simply uses his scrapers, pike poles and hooks to remove the bung and gain access for his own equipment."

Male variable checkerspot butterflies are among the creatures that 'plug up' their lovers' genitals to prevent them from remating.



The aquatic insect with the world's loudest penis

The male water boatman species, found across Europe, is only two millimetres long but has been officially recognised as having the world's loudest penis.

Researchers found that the creature is noisier than any other animal on the planet relative to its body size.

16 The male water boatman is only 2mm long - but has the world's loudest penis Credit: Alamy

Anne says it competes for females' attention by making music - using its abdomen as a string and its penis as a bow to 'play' itself and attract potential mates.

The chirping noise it creates can reach a staggering 99.2 decibels - the equivalent to sitting in the front row listening to a loud orchestra playing'.



The bees whose testicles explode at orgasm

For male honeybees, reaching orgasm isn't the joyful climax of sex. Instead, it means a horrifying, violent death that sees their testicles explode.

The males, known as drones, are fed by female worker bees and have only one task during their short lifetimes - to mate with a new queen bee.

16 Male honeybees' testicles explode when they reach orgasm Credit: Getty - Contributor

But they pay a heavy price for fulfilling this role - because their sex organs split open and tear loose from their bodies, leading to their deaths.

The queen bee, however, survives - and often mates with several members of the swarm.

"She saves up all the sperm cells (as many as 100 million) in a special internal sperm bank and doles them out as needed over the rest of her life," Anne says.

16 Female worker bees feed the male drone bees - whose only role is to mate with the queen Credit: Getty - Contributor

The sap-sucking critters who experience 'virgin birth'

Several insects are 'periodic practitioners of virgin birth', according to Anne. This means they can give birth without actually having had sex with a male.

Female aphids - sap-sucking insects - are an example of this, and can even give birth to children who are ALREADY pregnant.

16 Female aphids can give birth without actually having mated with a male Credit: Getty - Contributor

In these 'Russian doll' cases, the aphids contain baby aphids - developed from unfertilised egg cells - that are already carrying new female aphids themselves.

"They come out adult females who are actually pregnant themselves," Anne says.

A downside of 'virgin' birth is that all of the aphids are genetically identical.



And... the spiders who die in the middle of sex then are eaten by their loved one

In the world of spiders - distant relatives of insects - some hungry females gobble up their partners after they've finished having sex with them.

Among the victims are male American fish spiders, who are not only eaten by their partners but also suffer horrendous deaths in the middle of sex.

16 Male American fish spiders suffer horrendous deaths in the middle of sex Credit: Getty - Contributor

Similarly to honeybees, these spiders' sex organs explode when they reach orgasm. They are then eaten by their lover - for the sake of the kids.

"Even though his chosen one is a chubster, 14 times his weight, his little body still provides a useful protein boost," Anne says.



'We should care more for insects'

For every human being living on Earth today, there are more than 200 million insects.

And we rely on them for many reasons.

16 Anne's new book, Extraordinary Insects, is released on Thursday

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Anne says: "We need them for pollination, decomposition and soil formation; to serve as food for other animals, keep harmful organisms in check, disperse seeds, help us in our research and inspire us with their smart solutions."

She is now calling on the public to take better care of the creatures, who 'really save our lives every day', saying: "We should care more for our own sake and for their sake as well".