Under the bright yellow petals of a tarweed plant, an insect known as the assassin bug kills its caterpillar victim by stabbing it over and over. But does this perpetrator have an accomplice? Sticky droplets all over the plant could be a clue.
Just beneath the petals of this flower, a brutal murder is in progress. This was the victim, a few minutes earlier: a caterpillar. Before it got whacked, it was on its way to becoming an owlet moth. And this is the perpetrator. Pselliopus spinicollis, aka the assassin bug. It dispatches its victims with this sharp weapon. When it’s not using it, it keeps it folded up, like a switchblade. Let’s review that crime footage again, shall we? Yep, the assassin bug is definitely the hit man. But did it have an accomplice? The scene of the crime is this tarweed. Pretty, right? But what are these glossy droplets all over the place? A few nights back, this midge got trapped in them. So did this snakefly. Turns out, the tarweed lured them with these sweet, lemony droplets. This plant is an insect graveyard. Those bodies are a bribe for the assassin bugs, so they’ll take care of the plant’s caterpillar problem. See, the caterpillars eat its flowers. No flowers, no pollen. No pollen, no reproduction. Now that they’re on the tarweed, the assassin bugs mate and lay an egg or two right next to the cadavers, so their offspring have something to eat when they hatch. Then they get to work on that job for the tarweeds. The bigger caterpillars put up a fight. The little ones, they’ll try to make themselves scarce, dangling down on a line of silk. But plenty of them end up like our murder victim. Sucked dry. With the caterpillars out of the way, the tarweed mastermind can hang onto its flowers – and spread its pollen – for one more day.
1. What eats the tarweed?
2. Talk about the symbiosis relationship of the assassin bug and tarweed.
3. How does a tarweeds become an insect graveyard?