Sometimes it's hard to distinguish between a science experiment and a scene in a splatter movie. To conduct some ghoulish tests on spiders, scientists constructed forests of "frankensquitos" — made from parts hacked off their mosquito compatriots.
"What did you do today, dear?" These are the words that you never want to ask a scientist. Sure, there are days when the answer could be, "fought back against global warming," or "found a way to stop the bees from dying out," but then there are going to be days when it's, "customized hell's action figure collection." The experiment I'm about to describe took place on one of the latter days.
The first distressing fact that comes out on these days is that there is such a thing as a vampire jumping spider. This spider seems to be remarkably well fed, and it has a particular diet. It enjoys the female anopheles mosquito, right after she has gorged herself on blood. The puzzle is, this spider is surrounded by juicy bugs — and yet manages to feed almost entirely on this one kind of insect. Spiders aren't known for their intellect. Most of their brain power goes to food, sex, and timing their motions so that they're cresting the edge of your bed to greet you just as you open your eyes in the morning. So scientists at the University of Canterbury, New Zealand, wondered where the spider got the visual and mental processing power to pick out that particular prey, out of all the other options.
To figure out what cues the spider was looking for, the scientists took a look at the mosquitos. The blood-fed females had engorged red abdomens and lightly feathered antennae — as opposed to the smooth bodies of the unfed and the heavy antennae fluff of their male compatriots. To narrow down exactly what it was that set the spiders off, scientists went full-on House of Wax. They ripped apart various mosquitos, combining thoraxes, abdomens, and antennae from males and females to put together lots of different frankenquitos. They even injected the abdomens of some of them with a clear solution, so it would have the shape, but not the color, of blood-fed mosquitos. They then propped them up at the angle they would be if they were resting on branches, in horrific tableaux, and let the spiders loose on them.
Ximena Nelson, one of the research scientists involved, summed up how smoothly the experiment went in one classic sentence in the press release: "The great thing about jumping spiders is they're very decisive." Yes. That is great. In this case, it meant that they consistently and quickly chose prey most like their ideal food. When both mosquitos propped up in front of them had the same shape, they pounced on the one with the female antennae. This showed the scientists that the spiders could evaluate many different criteria before attacking their prey.
Nelson is, she admits, unable to see how the spiders relatively tiny brains could process so much, and hopes to conduct further experiments to determine whether the spider works its way down a check list of physical traits, or whether it has one whole picture that it evaluates at once. This means, clearly, more experiments — and more friends and family who, when they see the scientist coming through the door, will shudder like they're in the presence of Michael Corleone, and never, ever ask about their business.