Thursday, June 19, 2014

Successful rescue

I've been watching a pretty brown spider just outside my door. The other day, she had a new meal, a green grub of some sort.

As found, all tied up.

When I was taking its photo, it moved, struggling feebly against the web.

Sorry, spidey; this one's mine. I pulled the critter out of the web with an eagle feather I keep on hand. It took some doing; that's a very sticky web!

I thought my efforts may have hurt the grub, but after a rest, it stretched out and walked away.

Interesting stubby feet in the centre. And big, staring eyes.

Nibbling at the foamy I had it on. "Nah! Not edible!" And off he went.

I couldn't identify this, and sent it in to BugGuide. It's a sawfly larva, in the Tenthredinidae family. Jeff Brown, the BugGuide contributor who identified it, wrote,
"You can often differentiate Sawflies from Caterpillars by the prominent eye spots and the number of prolegs."
The legs are the first three pairs of walking legs; these will be retained in the adult sawfly. The prolegs are the stubby pegs that are visible in the coiled photo. This grub has 7 or 8 pairs. Butterfly caterpillars have variable numbers, up to 6 pairs. The adults, of course, have no legs, pro or not, on the abdomen; the 6 adult legs are attached to the thorax.

A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the order Lepidoptera, though they can also be found on other larval insects such as sawflies and a few types of flies. ...
... Although the point has been debated, prolegs are not widely regarded as true legs, derived from the primitive uniramous limbs. Certainly in their morphology they are not jointed, and so lack the five segments (coxa, trochanter, femur, tibia, tarsus) of thoracic insect legs. Prolegs do have limited musculature, but much of their movement is hydraulically powered. (Wikipedia)

I released my grub outside, a good distance from the spider's corner. The spider sulked overnight, then rebuilt her web from scratch.


  1. Interesting!!! I am not overly interested in larvae, so this was my first close look at one. Thanks! I really needed another thing to study...

  2. Wonderful that you were even able to find out what kind of caterpillar you rescued.

  3. The BugGuide people are so very helpful!


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