Insect Picture of the Day

Click for larger version

This garden spider picture was taken by Jarek Kucek and sent in by his coworker, reader Kit Watson. It’s a female Cross Spider, Araneus diadematus, which is another one of the larger orb weavers. They can reach up to 3cm body length. The name Cross Spider comes from the pattern on her abdomen.

You can tell it’s a female by checking the pedipalps. Males have pedipalps with tips so swollen that they look like little boxing gloves; females will catch you staring and say “Ahem. My face is up here.” This particular spider says it with a charming British accent: Kit and Jarek send us this picture from England.

If you look carefully at the larger resolution image, you can see how she clings to her web: the silk is pulled in under tension where each foot makes contact. Yesterday I said that the radial lines are not sticky while the spiraling lines were; I should point out that at the center of the web, none of the silk, radial or spiral, is sticky. You can’t really see it here, but in other webs, you can often see two separate spirals: the outer spiral is made of glue silk, while one at the center is for the spider to lair on and is made of dry silk.

Another detail from the large resolution: there is a dark-colored lump underneath her. It looks like it could be the head of a fly; if this is the case then this spider is quite small for a cross spider, perhaps only a centimeter long. Of course, it could be a horsefly, in which case this diadematus could be pushing 2.5cm after all.

It’s really hard to tell from the photo. I’m going to tell my friend Randy that it’s the head of a chihuahua.

I just swapped a quick e-mail with Kit; she says that, from memory, the spider was perhaps 15mm long, plus or minus 5mm.  (Don’t tell Randy!)