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Photo#194182
Parancistrocerus Acarinarium - Parancistrocerus leionotus - female

Parancistrocerus Acarinarium - Parancistrocerus leionotus - Female
Richmond Green Park, Richmond Hill (N43º53'58.8"W079º23'51.3"elev.195m), York Region, Ontario, Canada
June 18, 2008
Size: 12 mm
This shot shows the acarinarium at the base of tergum 2 of the female Parancistrocerus specimen (males have it too), here still with a full load of mites that later dispersed. Few other Hymenoptera, such as Xylocopa (large carpenter bees), have this feature, which carries beneficial 'ninja' mites that may help to keep the nest clear of parasites (see wikipedia).
Might make a good glossary term, too?

Moved
Moved from Potter and Mason Wasps. Stunning shot! A brief overview of the relationship between potter wasps and mites can be found in the General Biology section of the Vespid Atlas.

 
Thank you!
I was hoping to not to use Wikipedia, and I should have realized this info would be in the Atlas! I'll know where to reference from next time, thanks for pointing it to me.

 
Wikipedia
Sometimes I don't trust Wikipedia either, but some articles are excellent and well documented. I always check the history; this particular one, as many Hymenoptera articles, was partly written by Doug Yanega and can be trusted.

Great photo!
I had read about acarinarium and seen sketches but never a photo and this one is great.

 
Thanks Beatriz!
Had I not bothered to key this specimen after keying the earlier one, I would have completely missed this opportunity. A recheck on the specimen now reveals an almost vacant acarinarium, with most of the mites nowhere to be found!

 
Aha!
One was already breaking ranks when you caught them. They made such an interesting pattern, except for that one!