WEBVTT 00:00:00.440 --> 00:00:06.460 [MUSIC] 00:00:06.460 --> 00:00:10.900 There’s nothing like walking through cool grass on a warm summer's day. 00:00:10.900 --> 00:00:15.559 But every Southerner knows that a barefoot stroll in the yard comes with risks… 00:00:15.559 --> 00:00:18.590 "Ow, ow! OW!" 00:00:18.590 --> 00:00:22.820 This fire ant mound should be a familiar sight to anybody who lives in the southern U.S. 00:00:22.820 --> 00:00:27.040 But you won’t see them marching around in little lines on the ground. We're surrounded by an 00:00:27.050 --> 00:00:31.800 underground network of foraging tunnels, but this is home base. And the best way to get 00:00:31.800 --> 00:00:35.929 to know what’s inside is to give it a poke. 00:00:35.929 --> 00:00:41.089 A fire ant’s main senses are touch and smell. The slightest disturbance and workers release 00:00:41.089 --> 00:00:46.559 alarm pheromones, a chemical signal that can raise the entire mound to defense within seconds. 00:00:46.559 --> 00:00:50.569 Anything sitting still is now a target, so let's get out of here. 00:00:50.569 --> 00:00:54.920 A fire ant’s bite isn’t what hurts. Their mouths only serve as anchors so they can curl 00:00:54.920 --> 00:00:59.559 around a sharp stinger and inject a dose of venom, a painful reminder they’re in the 00:00:59.559 --> 00:01:04.089 same order of insects as bees and wasps: the Hymenoptera. 00:01:04.089 --> 00:01:08.910 Insect researcher Justin O. Schmidt developed a pain index for Hymenoptera venom, mostly 00:01:08.910 --> 00:01:14.640 by allowing himself to be stung over and over. The tiny sweat bee, for instance, is a 1… 00:01:14.640 --> 00:01:19.980 “a tiny spark singeing a single hair”. The bullet ant scores a 4, the most painful 00:01:19.980 --> 00:01:25.680 grade, like “fire-walking over flaming charcoal with a 3-inch rusty nail in your heel.” 00:01:25.680 --> 00:01:30.250 Fire ants score a mere 1.2 on the Schmidt Pain Index, but they tend to sting multiple 00:01:30.250 --> 00:01:35.400 times, like this one did. It's already starting a local immune response around that venom: 00:01:35.400 --> 00:01:40.200 it's red, it's itchy, it's burning. It does not feel good. Within a few days the cells 00:01:40.200 --> 00:01:43.750 will actually die and leave me with a nice little white bump that I will not be able 00:01:43.750 --> 00:01:47.970 to resist popping. The things I do for this show. 00:01:47.970 --> 00:01:52.860 These stings have made fire ants a target of pure, unadulterated hate in the southern 00:01:52.860 --> 00:01:57.770 U.S., but it’s important to remember that just like us, these ants are an imported species. 00:01:57.770 --> 00:02:03.390 The red imported fire ant, arrived in the U.S. between 1933 and 1942, accidentally scooped 00:02:03.390 --> 00:02:08.300 from their home in South America, placed onboard a ship, and dropped in Mobile, Alabama. 00:02:08.300 --> 00:02:14.890 They left behind a hard life full of daily ant warfare, but in Alabama they found opportunity, 00:02:14.890 --> 00:02:20.620 few enemies, and a boy named Edward Wilson. E.O. Wilson would later become the world’s 00:02:20.620 --> 00:02:26.140 leading expert in ant biology, but as a teenage scientist in Mobile, he recorded the first 00:02:26.140 --> 00:02:30.380 known sighting of imported fire ants. Over the next two decades, as Wilson and other 00:02:30.380 --> 00:02:36.810 scientists watched these ants spread out from Alabama, southern farmers went into full freak 00:02:36.810 --> 00:02:37.930 out. 00:02:37.930 --> 00:02:40.150 [DRAMATIC MUSIC] 00:02:40.150 --> 00:02:45.290 Now, maybe it was because the nation still had war on the mind, or the ants had “red” 00:02:45.290 --> 00:02:50.880 in their name, but the US stopped at nothing to eradicate them. Retired World War II bombers 00:02:50.880 --> 00:02:55.850 took to the air loaded with pesticide, indiscriminately showering the South with millions of tons 00:02:55.850 --> 00:02:56.810 of poison. 00:02:56.810 --> 00:03:01.830 We’d later learn that the pesticides used were many times more toxic than DDT. 00:03:01.830 --> 00:03:07.270 E.O. Wilson called the bombing campaign the “Vietnam of entomology” and it was one 00:03:07.270 --> 00:03:11.930 of the inspirations for Rachel Carson’s “Silent Spring.” In the end, aerial pesticides 00:03:11.930 --> 00:03:17.640 did do a lot of killing, but instead of fire ants, it was mostly to livestock, birds, fish, 00:03:17.640 --> 00:03:19.260 and native ant species. 00:03:19.260 --> 00:03:23.680 Nature hates a vacuum. By wiping out the native ants, we made it easier for imported fire 00:03:23.680 --> 00:03:29.370 ants to advance. They’ve since spread from Florida to Texas… on to California, even 00:03:29.370 --> 00:03:35.880 to Mexico, China, and Australia. Solenopsis invicta seems perfectly evolved for invasion. 00:03:35.880 --> 00:03:40.690 Part of the answer lies in their how they reproduce. Hordes of winged males and future 00:03:40.690 --> 00:03:46.250 queens take to the air in massive mating flights. Pregnant queens then air-drop into new open 00:03:46.250 --> 00:03:51.470 territory free of competition, break off their wings, and bury themselves to give birth to 00:03:51.470 --> 00:03:52.489 new colonies. 00:03:52.489 --> 00:03:57.819 In many places, like here Texas, a genetic variation has made some fire ants lose their 00:03:57.819 --> 00:04:02.410 territorial nature. Many colonies here are home to many queens, they’re more densely 00:04:02.410 --> 00:04:07.780 packed than their territorial relatives, allowing them to spread like a creeping fungus instead 00:04:07.780 --> 00:04:09.660 of airborne seeds. 00:04:09.660 --> 00:04:14.709 Thanks to their tropical origins, during floods, entire fire ant colonies can clump together 00:04:14.709 --> 00:04:20.959 and float until they find a new home. They invade by land, air, and water. 00:04:20.959 --> 00:04:25.210 It’s no coincidence fire ants and humans are constantly running into each other. Fire 00:04:25.210 --> 00:04:30.389 ants crave disturbance, and humans provide that everywhere we go. Think of it this way: 00:04:30.389 --> 00:04:34.720 If you clear an area, take away the natural vegetation, the first thing to move back in 00:04:34.720 --> 00:04:40.210 are weeds, and so it is with fire ants: Tiny animal weeds. 00:04:40.210 --> 00:04:45.930 Like weeds, they're more annoying than dangerous, but imported fire ants cost $6 billion every 00:04:45.930 --> 00:04:50.910 year, damaging everything from golf courses to electrical equipment, where they sometimes 00:04:50.910 --> 00:04:56.560 nest. Eradication is impossible, but the answer to controlling them might come from their 00:04:56.560 --> 00:04:58.400 South American home. 00:04:58.400 --> 00:05:02.130 Tiny buzzing insects, barely visible to the naked eye. 00:05:02.130 --> 00:05:06.190 Ant-decapitating flies. Phorid flies - that’s their technical name 00:05:06.190 --> 00:05:09.610 - are one of invicta’s natural enemies back home. 00:05:09.610 --> 00:05:14.830 They hover over unsuspecting workers, zip down, lay an egg inside the ant, and fly away. 00:05:14.830 --> 00:05:20.100 That egg hatches, a maggot crawls into the ant’s head, eats everything inside, and 00:05:20.100 --> 00:05:24.080 eventually the ant’s head falls off. Scientists have imported these flies into 00:05:24.080 --> 00:05:29.770 the U.S. so they can be used as a biological control method. One fly can terrorize hundreds 00:05:29.770 --> 00:05:34.790 of ants, putting a whole colony on the defensive. These flies are super-specific to the species 00:05:34.790 --> 00:05:38.740 they attack, so scientists don’t think they’ll become a threat to native ants. 00:05:38.740 --> 00:05:44.900 But even if phorid fly control works perfectly, imported fire ants will remain permanent residents. 00:05:44.900 --> 00:05:48.199 The name “invicta” means “unconquered” after all. 00:05:48.199 --> 00:05:51.600 Just like the people who accidentally brought them here, these ants found themselves in 00:05:51.600 --> 00:05:56.570 a strange land of opportunity, just trying to make the best of it. The bright side is 00:05:56.570 --> 00:06:01.400 that after decades of studying how to kill ‘em, the fire ant now rivals the honeybee 00:06:01.400 --> 00:06:06.620 as the best understood of all social insects. And for all their stinging, they've taught 00:06:06.620 --> 00:06:12.110 us a ton about evolution, social behavior, and of course parasites that make your head 00:06:12.110 --> 00:06:13.120 fall off. 00:06:13.120 --> 00:06:17.300 Karl von Frisch said something about those honeybees that I think applies equally well 00:06:17.300 --> 00:06:20.759 to fire ants: They’re “…like a magic well, the more 00:06:20.759 --> 00:06:23.630 you draw from it, the more there is to draw.” 00:06:23.630 --> 00:06:28.240 Who knows, each time we walk barefoot through their little world, maybe they’ve just been 00:06:28.240 --> 00:06:33.000 begging to be noticed. Stay curious.