Biosphere 2 is a three acre complex of glass pyramids and geodesic domes with self-contained biomes, including tropical rain forest, grassland savannah, and marine ecosystems. Described as a "planet in a bottle," it was originally constructed in the late 1980s and early 1990s. By 1993 populations of the invasive long-horned crazy ant (Paratrechina longicornis) were discovered inside the supposedly closed ecosystems. The crazy ant is named for its peculiar erratic movements. It is easy to identify with its long legs and very long antennal scape (basal segment of antenna). By the late 1990s, virtually all the ants in Biosphere 2 were Paratrechina longicornis, feeding exclusively on honeydew secretions from scale insects and mealybugs (Order Homoptera) on many of the indoor plants. Biospere 1 is the planet Earth, and its terrestrial ecosystems are impacted by introduced ants. One case in point is the ubiquitous Argentine ant invasion of southern California.

Even with all the safety precautions, including sealed doors and elaborate air-lock system, the Biosphere 2 complex has been invaded by this small, long-legged ant from tropical Asia. It can survive in highly disturbed and artificial areas, including ships at sea. Since it can live indoors with humans, there is no limit to the latitude where it can exist. In fact, it has been reported in human habitats from Sweden to New Zealand, and may be the most widely distributed ant species on earth!

Another South American species of crazy ant in the subfamily Formicinae (Nylanderia fulva), is an aggressive exotic species introduced into the southern and southeastern United States. It is called the "tawny crazy ant" or "Rasberry crazy ant," and is named after the exterminator who discovered it in Texas, Tom Rasberry. Like Paratrehcina longicornis it is called a "crazy ant" because of its random (erratic), non-linear movements. Preliminary studies indicate that supercolonies of this species may be displacing the troublesome fire ant (Solenopsis invicta) and may even be a worse pest. Unlike the fire ant, they don't sting; however, they readily invade homes and even damage electrical equipment.

While looking through my vial of "long-horned crazy ants" collected at Biosphere 2, I noticed a tiny ant tangled with one of the Paratrechina longicornis. Its body length was only about 1.6 mm. In fact, when I replaced it in my vial I never saw it again! Maybe I dropped it in the process. Luckily I did get a few images of this fascinating minute ant. It clearly had 2 petiole nodes & small eyes, and keyed down to the subfamily Myrmicinae. Because there were no spines on the thorax, I eliminated all genera except Solenopsis, Monomorium, Strumigenys and Cyphomyrmex. Of the last 4 genera, only Monomorium has a 12 segmented antenna with 3-segmented club. Of course Alex Wild's outstanding images helped a lot, plus I found an excellent article about this species by James L. Wetterer in Myrmecological News stating that it occurred in Biospere 2: J.L. Wetterer, "Worldwide Spread of the Flower Ant, Monomorium floricola (Hymenoptera: Formicidae)." Myrmecological News 13: 19-27, April 2010.