World of Wonders

When we see things that aren’t, we miss the wonderful things that are.

It’s Not Easy Being a Spider

Two items I recently wrote for a children’s science and nature magazine:

Assassin bug vs. Spider!

When a leaf falls into a spider’s web, the spider can tell from the vibrations it hasn’t caught an insect. But when it feels fluttering insect wings, it knows dinner has arrived. It also knows to attack quickly, before its prey escapes. And when it feels vibrations from a weak insect, the spider moves in slowly. It knows its meal isn’t going anywhere.

Now, two scientists from Australia are studying how assassin bugs catch spiders using the spider’s own web. Anne Wignall and Phillip Taylor watched as an assassin bug used its legs to pluck the threads of a web. It didn’t vibrate the web like a leaf—then the spider wouldn’t come. And it didn’t vibrate it like an escaping insect—then the spider would attack too quickly. Instead, it shook the web as if it was a small, weak insect. The spider approached slowly, making it easy for the assassin bug to grab its prey.

Wolf spider vs. Sundew!

Different species of animals compete with each other—especially when they eat the same food. This usually happens with animals that are similar, like dolphins and tuna, or lizards and snakes. But now, a scientist from Florida has discovered an animal and a plant that compete for food. David Jennings studies wolf spiders and tiny plants called sundews. The sundew feeds itself by catching insects with its sticky spines. The wolf spider catches insects with its web.

Credit: Christopher V. Anderson, Univ. of South Florida

Jennings placed sundew plants in terrariums. Next, he put wolf spiders in with some of the sundews. Then he added insects. When a sundew had to share the food supply with spiders, the plant didn’t grow as well. And in the wild, he found that wolf spiders either built bigger webs when sundews were nearby—or they built their webs farther from their spiny competitors. It was as if they knew the sundew would “steal” some of their food!

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Filed under: nature

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