1. Hummingbirds can fly backwards.
2. Some spiders can grow bigger in urban areas.
3. Cicadas expand and contract their exoskeletons to make their loud calls.
4. When caterpillars metamorphosize, they digest themselves into a "soup," then reform into a butterfly.
5. The largest bat colony in the world in Bracken Cave, Texas, is believed to have 20 million bats.
5. Female insects of the genus Neotrogla have a penis and can have sex for up to 70 hours.
6. There's a mammal in Australia that has sex until it disintegrates.
7. During sex, flies create a buzz that can attract predatory bats.
8. Female black widow spiders sometimes kill and eat their male counterparts after mating.
9. Female komodo dragons don't need a male to reproduce.
10. Bald eagles court each other in the sky. They lock talons while freefalling, then soar upward before hitting the ground.
11. Female kangaroos have three vaginas.
12. Snakes have two penises, but only use one at a time.
13. Bumblebees can sense a flower's electric field and use it to find pollen.
14. Honeybees can taste with their feet.
15. And honey is believed to have an eternal shelf life.
16. Armadillos found in the U.S. nearly always give birth to identical quadruplets.
17. Elephants are pregnant for almost two years.
18. They're also believed to grieve for their dead.
19. Penguins have knees.
20. Wombat poop is cube-shaped.
21. Guinea pigs are neither pigs nor from Guinea.
22. Koala bears aren't bears: They're marsupials.
23. On a 95-degree day, hugging a tree in the shade could help a 25-pound koala lose up to 68 percent of its extra body heat.
24. Ostrich kicks can kill a human.
25. Male platypuses are venomous.
26. An octopus has three hearts.
27. Horned lizards can shoot blood out of their eyes to defend themselves.
28. Mantis shrimp have four times as many color receptors in their eyes as humans do.
29. Catfish use their entire bodies to taste things.
30. You can use a blue whale's wax earplug to work out its life history.
31. Dolphins can stay active for 15 days or more by sleeping with only one half of their brain at a time.
32. Some lobster species can live to be 50 years or older.
33. Lobsters pee out of their faces.
34. The Chinese soft-shelled turtle can expel urea, the main waste product in urine, out of its mouth.
35. Some turtles can breathe through their butts.
36. Each of a tarsier's eyeballs is as big as its brain.
37. A group of otters is called a romp.
38. A group of rhinoceroses is called a crash.
39. A group of porcupines is called a prickle.
40. Baby porcupines have soft quills at birth, which harden within a few days.
41. While moms hunt, emperor penguin dads fast for weeks and protect their egg from the cold with a special flap of skin.
42. Grizzly bear dads sometimes kill cubs, so moms find dens that are far away from males.
43. Seahorse dads carry fertilized eggs in their pouch and can give birth to hundreds of babies at a time.
44. Tardigrades are the only animal we know of that can survive in the vacuum of space.
45. Giraffes have sturdy hearts and high blood pressure, which help prevent fainting when they lift their heads from the ground to the sky.
46. Aging male giraffes go black instead of gray.
47. And that feeling you get when something is so cute you can't help but want to squeeze it hard is called "cute aggression."