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We humans might think that flowers are pretty good gifts for a first date, but many insects have their own nuptial gifts, and well, flowers they ain't.

Hosted by: Stefan Chin

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Sources:

https://www.sciencedirect.com/science/article/pii/B9780123942883000022
https://www.nhm.ac.uk/discover/toxic-talents-cyanide-moths.html
https://rcannon992.com/2020/08/16/black-and-red-and-poisonous-burnet-moths/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6099377/
https://www.sciencefocus.com/nature/eight-weird-and-disgusting-presents-given-by-animals/

https://uwm.edu/field-station/red-velvet-mite/
https://www.macalester.edu/ordway/biodiversity/inventory/redvelvetmite/
https://www.jstor.org/stable/3496883?seq=1#metadata_info_tab_contents

https://cdnsciencepub.com/doi/abs/10.1139/Z10-065
https://www.sciencedirect.com/science/article/pii/B9780123942883000022
https://www.jstor.org/stable/3496883?seq=1#metadata_info_tab_contents

https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/scorpionflies-and-hangingflies-mecoptera
https://texasinsects.tamu.edu/scorpionfly/
https://bmcecolevol.biomedcentral.com/articles/10.1186/1471-2148-5-25

https://www.discovermagazine.com/planet-earth/being-stabbed-with-a-mucus-dagger-is-not-even-the-worst-part-of-snail-sex
http://www.molluscs.at/gastropoda/index.html?/gastropoda/morphology/love_dart.html
https://academic.oup.com/mollus/article/82/1/1/2460173
https://royalsocietypublishing.org/doi/10.1098/rspb.2014.3063
https://www.newscientist.com/article/dn8871-love-darts-double-snails-chance-of-offspring/?ignored=irrelevant

Images

https://www.istockphoto.com/photo/male-red-backed-shrike-is-feeding-female-gm475548390-65998745
https://www.istockphoto.com/photo/heart-shaped-box-with-heart-shaped-dark-and-light-chocolate-truffles-on-wooden-table-gm1066554826-285206047
https://www.istockphoto.com/photo/various-chocolates-pralines-gm1263096171-369670804

https://en.wikipedia.org/wiki/File:Zyga-2011-07-04.ogv
https://en.wikipedia.org/wiki/File:Six-spot_Burnet_(Zygaena_filipendulae)_caterpillar.jpg
https://www.istockphoto.com/photo/butterfly-pollination-02-gm1298563353-391398952
https://en.wikipedia.org/wiki/File:Red_spotted_moths_1_(3745889925).jpg

https://www.istockphoto.com/photo/red-velvet-mite-gm517310449-48626644
https://www.istockphoto.com/photo/red-spider-in-green-moss-gm1323888598-409406223
https://www.istockphoto.com/photo/red-velvet-mite-gm1133607620-300926991

https://commons.wikimedia.org/wiki/File:Carolina_Ground_Cricket_(Eunemobius_carolinus)_-_Gatineau_Park,_Quebec_2016-09-22_(01).jpg
https://bioone.org/journals/florida-entomologist/volume-85/issue-2/0015-4040_2002_085_0317_TSFIGC_2.0.CO_2/TIBIAL-SPUR-FEEDING-IN-GROUND-CRICKETS--LARGER-MALES-CONTRIBUTE/10.1653/0015-4040(2002)085%5B0317:TSFIGC%5D2.0.CO;2.full?tab=ArticleLinkFigureTable

https://en.wikipedia.org/wiki/File:Panorpa_communis_with_prey_Diogma_glabrata_glabrata.jpg
https://en.wikipedia.org/wiki/File:Panorpa_communis_2006-07-11.jpg
https://www.istockphoto.com/photo/scorpion-fly-gm1144428307-307668019

https://www.istockphoto.com/photo/snail-sex-two-snails-making-love-gm1288125555-384176491
https://www.istockphoto.com/photo/vineyard-snails-during-mating-gm687031748-126234471
https://www.istockphoto.com/photo/snail-gm178281866-20023217
https://www.istockphoto.com/photo/snails-mating-gm870060128-145666667
Thanks to Brilliant for supporting this episode of SciShow.

Go to Brilliant.org/SciShow to get 20% off an annual premium subscription for yourself or someone else! [ INTRO ♩] Humans have some odd customs around gift-giving and courtship. I mean, chocolate is this one specific tropical bean that's been fermented, roasted and mixed with sugar.

But on a first date, it tends to go over pretty well. However, humans aren’t the only ones who bring gifts to a potential mate. Gift giving is a behavior that occurs in many species across the animal kingdom.

And these gifts do more than make a good first impression. They generally provide substantial benefits that ensure a better outcome for the pair’s offspring. But the gifts themselves can be, well… chocolate they ain’t.

So from poison to mucus and a few bodily fluids in between, let’s explore a few creatures who take gift giving to a whole new level. Six spot burnet moths bestow upon their potential mate a toxic gift: actual poison. These critters have a deadly talent that develops when they’re just a wee caterpillar.

They’re able to produce hydrogen cyanide, a chemical that, in high enough concentrations, can even be deadly to a potential predator. These critters incorporate some of the toxins that plants make as a chemical defense against pests, and their bodies convert them into hydrogen cyanide. This chemical causes them to have an unpleasant taste, so predators tend to steer clear.

The red spots on the moth’s bodies serve as a warning to keep away. And during the mating process, the male moths are able to transfer some of their cyanide to the females. Not to kill them, mind you.

Instead, researchers believe that they are passing it along for additional protection against potential predators. This gift is like the insect equivalent of gifting a couple dozen roses, because the process of creating the cyanide is fairly energetically costly for the moths. Female moths are capable of producing cyanide too, and actually emit plumes of it to attract a mate.

But the males still gift them a little extra during courtship, which allows the females to put their energy into laying eggs while keeping their defenses up. The female also uses some of that poison to coat her eggs with, as an added layer of protection against potential predators. And researchers have found that the females value how much cyanide is gifted to them, preferentially choosing a male based on how large his cyanide gift was.

Which may mean these moths are becoming more toxic over time, as the females are constantly selecting for large cyanide gifts. Thanks, it’s… just what I’ve always wanted. The red velvet mite goes to great lengths to woo a mate.

The male doesn’t just bring a gift; he builds a beautiful, intricate space for his potential mate. and this little mite creates an elaborate set up out of sticks, leaves, grass, and... sperm. Researchers tactfully refer to this as a love garden. The sperm is dotted all over the sticks and grass, acting as both decoration and a sticky web holding all of the pieces of the meticulously designed space together.

Once constructed, the male leaves an intricate path of silk leading up to the space for a mate to find. Then he sits in front of his masterpiece until a potential mate wanders by and notices his handiwork. And When a potential mate does come along, the male will perform a little dance in front of the space, as a way of capturing her attention and enticing her into coming closer.

And if the female mite is intrigued, she will enter the garden he’s created, to investigate the space further. If the female sits down in that space, the sperm can impregnate her. Unfortunately, the competition for a mate can be stiff among mites.

That same trail he wove for his mate to find can be discovered by another male instead. The other male will immediately tear down the garden and build up his own in its place, as a way of ensuring it’s his sperm that contributes to the next generation. So, red velvet mite have got to be fancy and quick, in order to catch a female before the competition swoops in!

It does make sense for sperm to be involved during courtship… but that’s far from the only bodily fluid on offer. For example, some creatures will offer up their own /blood/ to their mates during the mating process. Ground crickets give their mates access to their blood, or rather their hemolymph, which is the insect equivalent of blood.

Male ground crickets have evolved large spurs on their tibia for female ground crickets to chew on during mating. That gives female access to the male’s hemolymph in the process. Researchers believe that this gift provides specialized nutrition to the females, who gain access to nutrients that they might otherwise be lacking in their diets, including protein, fats and carbohydrates.

This comes in particularly handy for the female during egg laying, which is energetically costly. In fact, researchers have found that female ground crickets have a preference for large males over smaller ones, because the larger the male, the more hemolymph a female can get from his spur during mating. While it’s likely this is not really a very pleasant experience for the male, it’s a sacrifice that makes sense for the survival of his offspring, because a well-fed female will have more energy to put towards high quality eggs.

As a result, much like the burnet moths are selecting more poisonous mates, the female ground crickets are shifting the size of the overall population towards larger males. Now, a gift of blood might be too much of a sacrifice to make, so how about some spit instead? While hocking up a big loogie in front of a date is typically considered bad form among humans, that’s pretty much what male scorpionflies will do for their potential mates.

Scorpionfly males have evolved enlarged salivary glands, specifically for the ability to produce large balls of spit. Interestingly, only well-fed scorpionflies have the ability to produce spitballs. Those that are malnourished will choose to offer up a dead bug instead.

Now if you ask me either of these gifts sound less than appealing. But researchers believe that, much like our cricket example, scorpionflies offer spit to provide the females with additional nutrients prior to egg laying. Which is why a dead bug proves to be a decent substitute for a giant ball of spit, if a male is unable to produce any spit himself.

The female snacks on the spit during the mating process, which ensures that she’s well fed enough to pass the male’s genes along to the next generation. And sometimes, whether they can’t make spit or just want to avoid making spit in the first place, male scorpionflies will pretend to be females and steal the spit snack right out from under a competitor! The females select a mate based on their ability to produce a lot of spit.

The more spit, the more likely they are to prefer that individual. And I say Cheers to that! Now our next animal has quite a pointed way of interacting with its mate, mutual stabbing, with a snot coated dagger.

Could you imagine being stabbed in the side on a first date? But don’t worry, because you’ll be stabbing them back. With a snot-coated dagger.

While this sounds awful, this is a behavior frequently observed in land snails. And this isn’t just a gentle poke. Researchers have observed snails retracting rapidly after being stabbed, suggesting this is a fairly painful process, yet it’s a behavior that they frequently perform during mating.

Most land snails are hermaphrodites, which means that they have both sperm- and egg-producing reproductive organs. And during the mating process, some species of snails will stab each other with what researchers refer to as love darts. These love darts are made up of a hard piece that makes them sharp and dagger-like.

They are also coated in mucus. The hard part can be made up of a few different compounds, depending on the species of snail. Some use calcium carbonate, while others use a more flexible material like chitin or cartilage.

Now, these darts are not to be confused with a penis. Each snail has one of /those/, too. And the snails /can/ mate without the love darts.

Once they use the dart, the snails need some time to regrow it, sometimes taking up to a week to generate another one. But researchers have found that snails who mated shortly after being stabbed by a love dart were twice as likely to sire offspring as those who aren’t stabbed. So Scientists believe the love darts are a way to encourage successful reproduction.

The mucus on the darts contains a pheromone-like compound that targets the snail’s egg-producing organs, encouraging them to store the sperm they’re receiving from the other snail. While all of these gifts sound fairly unusual from a human perspective, they’re particularly interesting to consider from an evolutionary point of view. These unique choices for gifts play important roles in mate selection, and have probably helped to determine the evolutionary history of these species.

With the exception of the land snails, most of the females are /actively/ selecting for a mate that produces their preferred gift in the right size, shape or quantity. Researchers are always eager to learn more about the process of gift-giving in creatures, since very little is known about how these abilities evolved and were selected for with time. But if you ask me, I think I’ll just stick to bringing flowers and chocolate on a date!

That said, if you are looking for gifts this holiday season, Brilliant is great for the relentlessly curious person in your life. Brilliant’s online courses in math, science, engineering, and computer science are designed to help you learn through interactivity. It gives you the satisfaction of letting you work through problems yourself, with explanations for any time you get stuck.

Courses are even available offline through their iOS and Android apps, so you or your lucky gift recipient can keep learning on the go or with a spotty Internet connection. The first 200 people to sign up at brilliant.org/scishow can save 20% off an annual premium subscription to Brilliant, which you can also apply toward a gift subscription. So thanks for checking them out! [ ♩ OUTRO ♩ ]