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Cannibalistic female spiders who chow down on males do so to give their fertilized eggs a developmental boost, a new study suggests. Researchers found that those Mediterranean tarantulas who ate their suitors produced more offspring, and those spiderlings were stronger and bigger than the offspring of tarantulas that had stuck to more natural prey.

The study turned up several surprises. The researchers watched the tarantulas’ behavior in their natural environments, and saw that the female spiders didn’t eat their mates–instead they waited until after they had mated, and then devoured the next unlucky suitor who came along. Some other studies have suggested that males may sacrifice themselves for the sake of their offspring, but this study showed that, at least in this species of spider, the males are purely unlucky victims and only the babies benefit [Reuters].

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In a striking example of the evolutionary benefits of altruism, researchers have found a species of ants that sends a few workers out each evening on a suicide mission to ensure the continued survival of the colony. The tiny ant Forelius pusillus, which makes its home in sugar cane fields in Brazil, makes a nightly ritual of covering the entrance to its nest with sand. To be sure that the entrance is sealed shut tightly, a few ants remain outside each evening to finish kicking sand over the hole. Those ants, stuck outside in the cold and the wind, die during the night.

“In a colony with many thousands of workers, losing a few workers each evening to improve nest defense would be favored by natural selection,” said co-author Francis Ratnieks…. The ants stuck outside might be old or sick, [co-author Adam] Tofilski conjectured. Thus, they may have essentially sacrificed themselves for the greater good, being more expendable members of the colony [ScienceNOW Daily News].

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Paleontologists have dug up the bones of a chicken-sized dinosaur that scampered through the Cretaceous forest 70 million years ago, feasting on termites and other insects. The Albertonykus borealis is believed to have lived like an anteater, using strong claws to rip apart logs for insects as food [Globe and Mail]. The dinosaur, found in fossil-rich Alberta, Canada, is the smallest ever discovered in North America.

The small dinosaur looks like a creature from a Dr. Seuss book, said [researcher Nick] Longrich, who called the findings “pretty cool.” … Most of the bones dug up in North America have been from large animals, he said. “Now that we are finally starting to find some of the smaller ones it is suggesting that our picture of the fauna is skewed. We are primarily picking up the big skeletons. They just preserve better” [CBC].

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A newly discovered ant from the Amazon rainforest is so strange that researchers have named it “the ant from Mars.” Found in Brazil, the ant has a pale body and no eyes, says [lead researcher] Christian Rabeling…. Its mouthparts stick out like sharp forceps and are longer than the rest of its head. Its DNA may be even more interesting. Genetic analysis puts the new ant so far from other species that it deserves its own subfamily [Science News].

Researchers named the subterranean ant Martialis heureka, which translates to “eureka ant from Mars,” because of the new species‘ odd morphology and because of their own excitement over finding it. Researchers say that a DNA analysis suggests that the M. heureka evolved earlier than any other living ant, and that it has changed little over 50 million years. “This discovery lends support to the idea that blind, subterranean predator ants arose at the dawn of ant evolution,” Rabeling said [LiveScience].

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In a match-up between an annoyed human brandishing a fly swatter and a buzzing fly, who wins? As most people know from frustrating experience, all too often the fly easily evades the human’s swat, and buzzes merrily into another region of the room. Now, using a high-speed camera, scientists have determined just how the fly makes its astoundingly effective escape.

Biologist Michael Dickinson used a video camera that shoots 5400 frames per second to record a fly’s precise motions when threatened with a swatting. The video showed that as a threatening object moved towards the fly from one direction, it shuffled its feat and positioned itself to take off in the opposite direction–all within 200 millisecionds. “They perform an elegant little ballet with their legs,” says Dickinson. “They move their legs around to reposition their bodies so that when they do jump, they will push themselves away from the looming threat” [NPR].

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