If yesterday's release of Starship Troopers: Marauder has you constantly scratching your back or hearing imaginary grasshopper sounds, you might not want to read any further. Then again, perhaps the best way to allay your fears is to confront them — and learn everything you can about the gargantuan cockroaches, beetles, and spiders that might be chirping with malevolence underneath your refrigerator at this very moment. Just don't blame us if you can't sleep tonight.The Bugs - or Arachnids - in Starship Troopers are at least three times bigger than the average member of the Mobile Infantry forces. This may seem comfortably outlandish from where you're sitting (hopefully with an armrest of bug-free Coca-Cola and a lap full of untainted popcorn) in the theater, but in prehistoric times, it actually was possible for arthropods to grow almost that large. Insects in that oxygen-rich atmosphere could easily suck up nourishment through their trachea, and that's why creatures like the Jaekelopterus rhenaniae (an 8-foot sea scorpion) and the Arthropleura (an 8.5-foot millipede) walked the earth. Nowadays, however, having an open circulatory system isn't such a piece of cake. Arthropods have no blood vessels to transport oxygenated cells in their bodies, so they must wait for the oxygen to diffuse through their body tissue — and the oxygen concentration in the air is a lot lower now that there are six billion humans hogging it, too. So you won't be seeing 8-foot insects in your house anytime soon, but the present day still offers us a host of shudder-worthy members of the phylum arthropod.

Giant burrowing cockroach. This crawly fellow, which hails from Australia, is the longest and heaviest type of cockroach on Earth. Measuring up to 8 centimeters and weighing in at 35 grams, it narrowly beats the giant cockroach, or blaberus giganteus.) Apparently some people keep giant burrowing cockroaches as pets; I wonder what the vet says when they show up.

Hercules beetle. In May, a few of these babies caused quite a stir when they showed up inside packages at a Pennsylvania post office. Customs officials were probably nonplussed to discover beetles that were fifteen centimeters in diameter — but I'm sure they felt better when they found out that the largest Hercules beetles can reach up to seventeen centimeters.

Phobaeticus serratipes. This is the longest known insect, a stick bug that has reached up to 55 centimeters on record. That's only with legs fully extended, however, so I'm sure that makes you feel better. The Phobaeticus lives in Malaysia and Singapore, and catches the eyes of a few pet owners there, too.

Goliath birdeater. The most traumatic event of my childhood was discovering a 20-centimeter-long spider on the floor of my bathroom, but it turns out things could have been much, much worse for me. In the rainforests of South America, 30-centimeter-long spiders lie in wait — and oh yeah, they sometimes eat birds and mice. Ye gods.

Amazonian giant centipede. The Scolopendra gigantea is carnivorous, can grow more than 30 centimeters long, it might have as many as 46 legs, and its venom is dangerous to humans. It must be really, really adorable anyway, because people still keep Amazonian giant centipedes as pets — this guy in Trinidad, for example, looks pretty happy with his.

Japanese spider crab. This is the largest known arthropod on Earth today: Fully grown, it can reach a leg span of 4 meters and a weight of 20 kilograms. As if being huge isn't enough, this species also has a life expectancy of 100 years. Japanese spider crabs live at the bottom of the Pacific Ocean, and frankly, I'm happy to leave them there. Images from Australian Museum Online, DK Images, God of Insects, Weekly Echo, BigHairySpiders.com, and Wikipedia.