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It's the year 2018, and we now know that flies like to ejaculate. But how does this tie into our understanding of addiction?

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Animals need to like sex to keep doing it and having babies, but scientists aren’t always clear on which aspect of sex is compelling for them. Like, with male fruit flies, maybe it was something about cozying up to a female fly, or finding a really great grapefruit... maybe it was something else.

And in a study published on Thursday in Current Biology, Israeli neuroscientists found out that male fruit flies aren’t all that different from humans, because they like to ejaculate, too. For their experiments, they had to get the male fly to release his sperm without a female in the picture. Normally, this would be a hard nut to crack.

But oddly enough, scientists know which neurons trigger ejaculation in male flies. And because of a technique called optogenetics, they can genetically engineer certain neurons to turn on in response to light. This means researchers can make flies that ejaculate whenever the researchers want, just by flashing a light — in this case, a red light, which can pass through a fruit fly’s exoskeleton and hit those modified neurons.

The future is now. The team put these engineered flies into a box with a red light on one side, and then looked to see whether they hung out more in that space. If they did, it was a sign that they found it rewarding.

And did the flies ever! They strongly preferred the, well, red light district. But females and unmodified males wandered around and didn’t prefer any particular area.

Activating the ejaculation neurons a lot also increased the amount of a signaling molecule called neuropeptide F, which normally rises after lots of fly sex. So that’s another sign that the researchers are tapping into a natural reward circuit. The team still can’t say for sure whether pleasure comes from activating the ejaculation neurons, or from other signals related to releasing seminal fluid.

But it’s clear that flies like it. So… why…? Well, one reason why researchers are so interested in fly sex is because understanding basic reward systems could help us better understand addiction.

In fact, another clue that the flies like to ejaculate is because when they do, they drink less alcohol. Flies normally prefer alcohol-laced food to a normal version, but that's not the case after a few blasts of red light. In humans, it’s bound to be more complicated than that.

But researchers hope that they can use flies to dig deeper into the reward mechanisms at play when someone abuses or is at a higher risk of abusing a drug. So, one day, maybe a non-alcoholic toast to fly ejaculation will be in order. Our next bit of news also has to do with insect fluids, but… less fun.

Because, instead of fruit fly sex, we’re talking about ant suicide. This week, an international team of scientists reported the discovery of a new ant species in the journal ZooKeys. This ant blows itself up to fling a toxic, sticky yellow goo onto its attackers, and defend its territory.

Which…. I mean, kudos. That’s amazing!

I’m glad that I don’t have that particular defense mechanism, though. For obvious reasons, self-sacrificing by ripping your body apart, or what biologists call autothysis, isn’t a go-to defense mechanism for organisms—sharper teeth, stronger claws, speedier legs: more typical. But a few social insects, including some termites and ants, go this rather explosive route for the greater good of the colony.

Now, to be fair, entomologists have known about this ant for a while. It’s one of more than a dozen exploding ants in Southeast Asia that do some version of this bizarre defense mechanism, and was nicknamed ‘yellow goo’ or just ‘YG’ in earlier papers. These ants evolved extra-large chambers in their lower abdomen to hold their lethal goo.

When attacked, they squeeze their abdomen hard enough to rupture, and squirt it all over the enemy’s face. This gunk is so sticky that it binds the two insects together permanently. It can easily take out larger insects, or even multiple others at a time, which may explain its success.

And, according to these researchers, it has a spice-like smell. They did not go into how it tastes, but now I’m curious. But even though we knew about exploding ants, scientists hadn’t realized that this insect was unique enough to be its own species — until now.

The researchers used a few tools to figure that out, including genetics, field observations, and a detailed study of the physical appearance of lots of ants in Borneo, a big island in the southwestern Pacific ocean. Classifying ants can be especially tricky because the same species can have wildly different social castes. This explosiveness, for instance, only applies to smaller female workers.

The larger workers, or soldiers, actually have huge heads that are flattened in the front, which they can kind of use to barricade their nests. Males and queens also look totally different, and also don’t explode. The team studied one particular colony of yellow goo ants in the rainforest, which they estimated included thousands of individuals across multiple nests.

In fact, it spread out over at least 2500 square meters, or more than half an acre, and stretched as high as 60 meters up into the trees. And really, the main action is even farther away. Previous studies of exploding ants have found that, weirdly, the ants aren’t sacrificing themselves to protect their nests.

Instead, they’re protecting their foraging territory. This makes the ants outliers among kamikaze insects, too. Usually a more direct threat to the colony justifies the suicide, not just defending food sources.

In any event, this team of researchers is on the cusp of identifying even more new species, and there are plenty more exploding ants — and fluids — to discover. A huge thank-you to SR Foxley, our Patreon President of Space for supporting this not particularly brand-safe episode of SciShow. What will we do without you?

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