Into the darkness

I've been playing with darkfield microscopy - poor man's phase contrast. Darkfield uses obliqe illumination as a cheap optical trick to increase the contrast of transparent and traslucent specimens. It can produce dramatic images with dark backgrounds and usually features prominently in microscope photography competitions such as Nikon's Small Worlds. I started out with the somewhat translucent furca of a handy Isotomurus unifasciatus specimen. On the left is my conventional setup of top plus bottom illumination, post processed; on the right darkfield transillumination, both stacked with Zerene: 

The problem here is that inserting the darkfield disc into the light path lengthens the exposure time 20-fold and the image quality suffers as a result. Looking at the non-transparent abdomen of the same specimen (conventional illumination):

Darkfield plus supplemental top light:

I think this is the better result, but clearly I need to find some transparent specimens to get maximum benefit from darkfield. 

 

Sminthurus viridis ssp. cinereoviridis

I have to admit that springtails have been on the back burner recently while I've been focusing mostly on spiders. The weather hasn't helped but it's not an excuse, mostly I've been working on spiders. I have been recording springtails regularly, but I haven't posted anything publicly because I haven't found anything particularly interesting - until today. This morning the vacuum sampler turned up a whole bunch of these. After some rusty fumbling, they keyed out to be Sminthurus viridis (which I have found several times recently), but specifically Sminthurus viridis ssp. cinereoviridis (thanks to Frans Janssens for help with the I.D.).

Sminthurus viridis ssp. cinereoviridis has 2 spots on small abdomen. In the ecovariant nigromaculatus of S. viridis, 3 spots are present: https://www.collembola.org/images/stach/1956/Sminthurus-viridis-1956-J-Stach-Poland-PlateXXXII-Fig3.jpg There are supposedly difference in chaetotaxy of the setae on the subcoxa of the third leg, but I have found it impossible to image these. Steve Hopkins was reluctant to accept nigromaculatus as a separate species. As a dyed-in-the-wool taxonomic lumper, I wouldn't disagree. Frans Janssens calls it "Sminthurus viridis (ecovariant nigromaculatus)", which is said to be associated with sandy areas, heathland, moors, heather, etc. My specimens came from the wettest of wet water meadows alongside the River Soar and have 2 abdominal spots, so Sminthurus viridis ssp. cinereoviridis it is.

Before The Rains

A cautionary tale

For those who think they can tell Isotoma viridis from other Isotoma by the colour alone - two Isotoma viridis specimens from the same sample, one green, one not, confirmed by the manubrial teeth.

Some like it wet

I recently bought myself a G-vac - for the uninitiated, a cordless garden leaf vacuum adapted for use as a bug vac - and I took it for its second outing this morning. How do you convert a leaf vacuum to a bug vac? Well essentially you tape a net bag over the mouth of the inlet tube. On a recommendation from a more experienced bug-vaccer I bought a nylon jam strainer bag to use for this (others use net curtain material). Now I will admit that the primary reason I bought the bug-vac was for spider work, and I wan't at all sure the jam strainer bag would retain insects as small as springtails, but on its first outing a couple of days ago I was delighted to find it worked with large spiders all the way down to springtails, including the little ones such as Lepidocyrtus.

A week or so ago, pre-vac, I had done some sampling in wet meadows beside the River Soar. At that time I'd spotted a patch of Juncus sitting in a damp hollow that looked interesting but I didn't have time to go there on my first visit. This morning I decided to go back and take a look, this time armed with the bug-vac. Bearing in mind this is a piece of electrical equipment, albeit double insulated to EU standards and designed to suck up wet leaves, I'm pretty cautious about mixing electricity and water because the 36V battery in the bug-vac could give out quite a jolt. I was therefore a bit alarmed that the bug-vac started spitting water out of the inlet when I stuck it in the Juncus, but the point of all this dicing with death is that the bug-vac turned up (alongside more run of the mill species) my first ever Isotomurus plumosus in VC55. I'm delighted but I won't be pushing my luck too far.