Genus Tenthredo sawfly
What’s black and yellow and not a wasp all over? Meet the Genus Tenthredo sawfly.
Honest, this really is not a wasp, but its scientific name doesn’t do it any favors; “tenthredo” comes from the Greek “tenthredon” which means “a kind of wasp.”
Silly scientific name!
That said, tenthredo sawflies are related to wasps. They are both in the Order Hymenoptera which includes ants, bees, wasps and sawflies. This might make it seem like sawflies must be very similar to wasps, but animals within an order can be very different.
For example, cheetahs, wolves, bears and walruses are all in the Order Carnivora and you aren’t likely to mistake one for the other.
So, what is a sawfly? We’ve met a couple, but it’s been awhile, so let’s review.
Sawflies, as we’ve learned, are related to wasps and bees, but they do not sting. Some species can bite, but they don’t have any venom so while a bite might surprise you, it won’t harm you. As with most arthropods, a sawfly would only bite if it felt trapped or threatened, like if you accidentally sat on one, or one got caught up in your clothing.
The name “sawfly” comes from the females’ saw-like ovipositor which they use to cut slits into leaves, bark, individual pine needles or new shoots of their host plants. The females then lay their eggs into the snug spaces they’ve sawed.
Sawfly eggs and larvae in sufficient numbers can damage the appearance of the host plant, but rarely damage the health of the host plant.
Most sawfly larvae look like caterpillars. They have more prolegs (working legs) and are always smooth and hairless. Sawfly larvae are more social and feed in large groups versus the solitary life most caterpillars live.
If a group of sawfly larvae feel threatened, they will all raise up the front half of their bodies in unison, hoping to scare away a potential predator by looking like one big many-armed critter. They put value in the “safety in numbers” theory.
Most sawfly larvae are brownish, green or yellowish-green and generally have black or dark brown heads. As they mature they develop spots or stripes on their bodies to give them better camouflage.
As you can see in the photo, adult tenthredo sawflies abandon camo for mimicry. In nature looking a lot like a wasp is just about as effective as being a wasp when it comes to making a predator think twice before trying to make you a meal.
Tenthredo sawflies are in the common sawfly family along with 900 other species (give or take). You’d think it would be hard to stand out in a family that size, but tenthredos manage to do so.
How? Most adult sawflies eat pollen and nectar (so yes, they are pollinators!), but tenthredos prefer a meatier meal. They chow down on flies and other small insects who visit flowers.
Adult tenthredos are about one half of an inch in length, so they can take out some decent-sized flying garden pests.
Tenthredos raise one new generation per year and have four life stages: egg, larva, pupa, and adult. You may begin to see the “caterpillars” as early as March and adults of various sawfly species will be on the wing through September.