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Monostegia abdominalis

Monostegia abdominalis
Ottawa, Carleton, Ontario, Canada
Size: 20 mm
Monostegia abdominalis larva preserved in acetone.

Images of this individual: tag all
Monostegia abdominalis Monostegia abdominalis Monostegia abdominalis

Moved from "Symphyta" - Sawflies, Horntails, and Wood Wasps.
John, this adult was reared from this larva, correct?

No - larvae preserved in acetone don't pupate very well :-(
I tried to rear half a dozen from the same batch of larvae as this one, had two successes of which this was one. (I took the other one apart while trying to ID it.)

Sawflies - Tenthredinidae
The adults pictured are Monostegia abdominalis (Fabricius) - Tenthredinidae, Allantinae - a species that feeds on Lysimachia. I can't tell if the larva is the same or not. It has not been recorded from Oenothera. Another species feeds on Oenothera - Erythraspides carbonarius (Cresson), but that species is all black.

thank you
Many thanks, Dr. Smith. It seems that this species was first recorded in Canada here in Ottawa in 1965 on Lysimachia nummularia.

The Oenothera macrocarpa was far more than a casual nibble - the second wave of several hundred was mostly raised on it, and despite daily patrols to pick them off, turned over a square meter of it to lacework. What is needed to register that? I have photos of the affected plant, but not photos of the larvae on the plant. However, I can't possibly have got them all, so expect them back next year on both plants.

The first Canadian record
may have been 1965. I don't have that reference. There is a publication on the biology of M. abdominalis in Quebec on Lysimachia terrestris (Price, P. W. 1970. A loosestrife sawfly, Monostegia abdominalis (Hymenoptera: Tenthredinidae). Canadian Entomologist 102: 491-495).

not Athalia
Got a reply from a Canadian expert at our National Insect Collection: antennae of Athalia are uniform diameter, mine expand like a baseball bat. He's invited me to bring the specimens in when he gets back from holidays early September.

Moved from ID Request.
Congratulations--sawflies are often difficult to rear. I've moved your images to the sawfly section for expert attention. If you got a photo of the pupa/cocoon, that would be a nice addition to the guide.

trying for pupa
I've only spotted one since the request, and it died in the rearing jar. I note that all the Athalia larvae images I've been able to find aren't anything like the white colour of these ones...

Sawfly larva (not moth or butterfly)
It's a Sawfly larva. You can tell by the large number of prolegs on the abdomen and by the single stemma (eye) on the head. Unfortunately I don't know which (there are many types); however, you can check here for some ideas (if not full identifications).

explains a few things!
like why I couldn't see any crochets on the prolegs... And, the adults were not parasitic wasps (at least I got the order of them right), but sawflies. I've added a photo of the adults. Starting with Hymenoptera, Chu leads to subfamily Tenthredinidae, then web photos suggest genus Athalia, but further suggestions are most welcome.

Many thanks, Peter.