Name That Culprit

[Allyn]

This morning, I found a top leaf on one of my tomato plants had been turned into an incubator (I'm assuming). Any ideas as to whether it's a pest or a beneficial? The tip of the leaf is folded down to make a pocket. I pinched it off, but wanted to identify it before I decided whether to squish it.

[imafan26]

My guess is one of the many species of web worms. They are usually caterpillar larvae and they usually emerge late May through to July.

[GardeningCook]

Toss it. Nothing that does that to a tomato leaf is in any way beneficial.

[applestar]

I always check to make sure that sort of thing is not a spider's nest, because if it's a spider, I want it to live on the plant guarding it, and eventually hatch a nestful of babies -- babies are great for handling the tiny pests that adult spiders might overlook.

Also, trichogramma wasps emerge from a caterpillar to make a pupae mass that looks like lumpy cottony lint, so I would look twice at that sort of a mass, in case they have been snacking on hornworms, climbing cutworms, and tomato fruit worms (though it's more likely to see braconid wasp pupae which are individual rice grain like ovals on the back of a hornworm).