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Stem Sawfly 1 - Calameuta clavata - male - female

Stem Sawfly 1 - Calameuta clavata - Male Female
North of Boulder Creek, Santa Cruz County, California, USA
May 20, 2012
Mating pair on buttercup flower (Ranunculus californicus). There were a large number of these swarming over and landing on the buttercup flowers near a brook running through a grassy meadow surrounded by (mixed) redwood forest. It was a warm, sunny afternoon. Images from the same time/place/population appear in posts with thumbnail images below:

Initially I believed these were ichneumonids since there are many (>14) antennal segments; there appears to be no costal cell (or the bounding veins are fused/thickened...and yellow); there are two trochanter segments; and the dorsal tergites of the abdomen appear more sclerotized than the ventral sternites (see here). Those are a few items I noticed while trying to run these guys through the keys in Goulet & Huber(1) and Borror & DeLong(2). BUT...I made a major mistake at the very start in both keys...going with suborder Apocrita instead of Symphyta!

Thankfully, Ross Hill promptly corrected me...pointing me to stem sawflies (Cephidae). They happen to share the characters I noted above for Ichneumonidae (except perhaps for the "tergites more scleroterized than the sternites" part). Indeed, Goulet states (on pg 101) that in Cephidae there's a "slight dorsoventral constriction between abdominal segments 1 & 2", and that "They are unusually slender for sawflies" and "to the untrained eye adults are very much like those of Ichneumonidae". That gave me a bit of consolation for my error :-)

After Ross's nudge, I studied the 1969 CIS publication "The Cephid Stem Borers of California (Hymenoptera: Cephidae)(3)" by W. W. Middlekauff and it became clear this was Cephus (see here for some details). Natalie McNear also used Middlekauff to key her post here, and noted that he remarked on the apparent affinity of Cephus clavatus for the pollen of buttercups, which was certainly the case for both this population and the one Natalie observed in Marin County.

Images of this individual: tag all
Stem Sawfly 1 - Calameuta clavata - male - female Stem Sawfly 1 - Calameuta clavata - male - female

Moved from Cephus clavatus.

Calameuta clavata (Norton). Cephids are often confused with ichneumonids, but the abdomen is more brodly joined to the thorax and the wing venation entirely different. These are commonly attracted to yellow flowers.
Note that the genus name has changed since Middlekauff. The only other species of Cephidae in CA that can be confused with this is Cephus cinctus, which is still placed in Cephus.

Thanks Dave
Funny...when I first saw =v= had moved my posts, I thought I'd erred *yet again* in the ID!

I then searched the web, found your Calameuta middlekauffi paper(1), and realized that there had been a name Natalie and I were on the right track after all when we attempted to ID our posts using (2) (shoo wee! :-).

BTW, the Calameuta info page had indicated there was only 1 nearctic species, so I edited it to indicate there are 2, and added a link to your 2005 paper(1). I also edited the C. clavata info page to indicate the synonymy with Cephus clavatus (for those who may use Middlekauff(2) and be led slightly Natalie and I were). And I added a guide page for Calameuta hopeful anticipation that a BugGuide contributor will be able to populate it with nice posts in the not too distant future :-)

Thanks -
for all the work, and you even found the 2005 paper. Your identification of clavatus was correct, its just that it is now put in another genus.

Moved from Stem Sawflies.


Stem sawflies…
See reference here.

I went with "base of abdomen constricted" in the keys...and thus was working in the wrong suborder!!

Many thanks, Ross, for setting me on the right track here.

I followed your lead, and this is apparently Cephus clavatus...assuming I got things right in this post:

(Please, let me know if I goofed-up :-)

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