A series of insect truths

1 . Blood bath. Speaking of circulatory systems, insects’ are way different from humans’. Rather than closed vessels such as arteries and veins shuttling blood around, insects have an open circulatory system, in which their blood, called “hemolymph,” bathes the organs. The insect “heart” is a segmented and chambered vessel running along the animal’s back. This vessel contracts to send hemolymph forward toward the head; from there, it sloshes around back into the rest of the body. Hemolympyh is typically clear but can be greenish or yellowish, as anyone knows who has seen certain bugs splatter on their windshield or underfoot.

2. Ancient critters. The oldest insect fossil — a set of jaws, actually — goes back 400 million years, suggesting insects were among the first animals to transition from sea to land. Insects, in other words, were around a good 170 million years before dinosaurs came onto the scene.

3. That’s a big bug. The largest insect ever known to have terrorized the skies is Meganeuropsis, or the griffinfly, which was an ancient dragonfly with a wingspan of up to 2.5 feet (0.8 meters). These ancient dragonflies preyed on other insects and small amphibianlike creatures during their reign from about 290 million to 250 million years ago.

4. Monsters and motes. The heftiest insect found today is New Zealand’s giant weta, a cricketlike beast that can weigh more than a pound. The longest insect, meanwhile, is Chan’s megastick, native to the island of Borneo and stretching over 22 inches (66 cm). The smallest insect, you ask? The evocatively named fairyflies from Costa Rica. In one of these wasp species, Dicopomorpha echmepterygis, the male is a mere 0.005472 inches (0.014 cm) long.

5. I see you . . . and you, and you, and you, and you! A prominent feature on insects is the compound eye, consisting of many individual visual units called ommatidia. A popular misconception (promulgated tongue-in-cheek in this section title) is that each unit acts as its own eye, each perceiving a total field of view. But in fact ommatidia act more like pixels, building up into a mosaic of imagery. The dragonfly is widely considered to have the most impressively ommatidia-studded compound eyes, with about 30,000 units per half-spheroid eye, according to researchers reporting in a 2012 issue of the online journal PLOS ONE. These ommatidia permit a nearly 360-degree field of view, handy for snatching flying insect prey out of the sky.

6. Bonus eyes. In addition to the two large compound eyes on either side of their heads, a number of insects have so-called simple eyes, or ocelli, in between, smack dab on their “foreheads.” Many flying insects’ ocelli form a triangle, with two aligned ocelli above a centralized third, looking more like an occult symbol than an independent visual system. The question of the ocelli’s function long stymied researchers. Recent studies have reported, however, that the ocelli, at least in dragonflies, seem specialized for detecting light, particularly when distinguishing the horizon, according to scientists writing in a 2007 issue of the journal Vision Research. As such, dragonflies can quickly differentiate up from down, as it were, and keep their bearings during acrobatic flight maneuvers, a feat of attitude-sensing that could work nicely for both piloted and unpiloted aircraft.

Other animal facts as tiger facts