In lieu of a reference...

After my rummaging through the big pile of reeds and straw a couple of weeks ago, I was still left with a few beetles to put a name to.

Many of these were the ptiliids, aka the dreaded featherwing beetles. There are a fair number of species and they don't get much above 1mm in length. There are keys but once you get to genus I find them pretty much useless. Partly because the differences are slight and partly because my microscope just can't cope with stuff that small at the resolution that is needed.

My preference is to dissect and hope for a female. Unlike, say staphs where the males naughty bits can elucidate an ID, for ptiliids it's the intricate spermatheca of the females that can be the clincher.

All the specimens I had were in the genus Acrotrichis, and look a bit like a mini trilobite with their tapered, pointed pronotal hind corners. My biggest issues is that in order to get the relevant bits out and get them under a microscope, I start with this...

...but end up finishing with this...

This means that I don't have any reference specimens for future comparison. Well I guess I could crudely try and reassemble the poor thing but it would be a fruitless task. 

I put the spermatheca in a tiny drop of glycerol and then put them under the compound microscope for some proper scrutiny, usually moving through the different planes of focus and try and sketch a rough picture of the hoops, twists and whorls.

So what I do have is a bunch of images of the spermatheca as a reference for future comparison.

So here are the ones from the visit...

Acrotrichis henrici

Acrotrichis montandonii

Acrotrichis fascicularis

The images don't really do these amazing structures justice. As Max Baclay said on twitter 'any sperm that can negotiate this deserves to fertilise the egg!'. And he's not wrong.

More tiny genitalia

I've yet to identify a Ptilid down to species level. I'm getting better at recognising the more common genera but I've struggled to go further.

So I can eyeball this one and be pretty sure it's an Acrotrichis.

Part of the problem has been with the dissection because a) they get no bigger than 1mm and b) you then have to find what you're looking for and get it in a state that is recognisable. 

Basically, I've just not been finding any genitalia.

Until now....

I had 4 individuals to practice on, so I got into a pattern.

1. Remove the head from the abdomen.
2. Manoeuvre the 2 micropins into the hole left by the head.
3. Gently separate the 2 halves of the abdomen.
4. Look in the end section of the abdomen for the bit you want and then remove it.
5. Get it on a slide under the compound microscope.

This worked and I was getting a spermatheca or aedaegus each time. Result!

I added a spermatheca to a drop of water but was honestly none the wiser!

Clive W on the Facebook page, suggested immersion in glycerol instead. Luckily I had some to hand.

The difference was amazing. I could see a lot of the fine detail. What an amazing structure. As someone else summed it up: it's like someone has been and violated a toy trumpet.

I flicked through the images in Duff Volume 1 and lo and behold this spermatheca is a dead ringer for Acrotrichus fascicularis, and one of the more commonly encountered species. Another new species for me and my first ptilid. 

Bring on the rest of them....