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Photo#286885
Caddisfly - Macrostemum

Caddisfly - Macrostemum
Pepperell, Middlesex County, Massachusetts, USA
June 7, 2009
Size: 8mm

Images of this individual: tag all
Caddisfly - Macrostemum Caddisfly - Macrostemum

Macrostemum zebratum
I must thank David and Lloyd for bringing this problem to my attention. I agree that the larvae fit the key and figures for carolina(-um) (in Ross), which caused some consternation on my part, as a quick examination of all our other larvae from NH in this genus revealed the distinct rounded tubercle over the eye also (= carolinum!).
The good thing is that we have adults from many of these sites also, including the Nissitissit River just 5 miles or so upstream from where Tom got his specimens but in NH. A few identified by John Weaver. Our larvae from NH are identical in head structure to Tom's, but the adult males we collected there are clearly zebratum (again using Ross/ids by Weaver). Unless Ross' adult key has been shown to be incorrect, I am going to continue using zebratum, but with a few qualms until some trichopterist looks into this situation.

 
further study
Don - if you wish to follow up further on this problem it would be good to send representatives of your adults/larvae to the DNA folks. They prefer material which was collected and stored in ETOH (or dry). If you haven't participated in the barcoding efforts yet you can contact Karl Kjer (KJER@AESOP.Rutgers.edu) or Xin Zhou [xinzhou@uoguelph.ca] for more info.

Further resolution of the associations would be great.

Dave

 
Thanks
if they are actively working on this problem, it is certainly not a big deal to get the larvae (if it's not too late) and adults from the nearby Cocheco River and pop them into 95% ethanol. They are very common in our large warm rivers here around Durham. Of course, the rivers here have been at flood level for the past month due to continual rain, and I've sort of given up on aquatic collecting for a bit.

 
It would be very interesting to see DNA results.
I suspect that many records for both species are probably based on either larvae or adults, but not both. Given what you have observed in your specimens, Donald, that would seem to be make such identifications problematic. From what I can gather, there is not a pronounced difference in male genitalia. Those problems might be further confounded by the distribution-based assumptions that Dave mentioned.

Moved
I guess I should wait for the specimen to be looked at. Who knows, it could be something more interesting than the Zebra.

Moved
The UNH site only lists this one species of Macrostemum. So I guess it's safe to call this one Macrostemum zebratum.

 
how safe is safe.......
I am not sure what the UNH list is based on (state, county, watershed, geological records)but the other two NA species are known from relatively nearby states. I am one who strongly discourages identifications based on reported distributions. Too many critters are placed into vials with a determination label based solely on a past distribution record. Those vials are almost never looked at again - whether the ID is right or wrong. Us folks who go through collections looking for new species/records focus on the vials with questionable species determinations (there is only so much time). I suspect it is the same for photos. And I have a recent example of new records. A couple years worth of collections from a fairly small, although interesting, part of NY resulted in the addition of about 50 species records (yet to be published) to the known NY State caddis list . The more we look the more we find. That is the best part of looking at critters :)

 
Dave makes a good point
When I was looking at this head shot, I thought there was a chance that it might be carolina.

Moved
Moved from Caddisflies.

Hydropsychidae
Macrostemum.

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