Notes on Scotophaeus blackwalli

The Mouse Spider, Scotophaeus blackwalli, is a familiar inhabitant of homes and gardens, but there is a fly in the ointment. There is a second species of Scotophaeus in the UK, S. scutulatus. However, although widespread in Europe, this is very rare in the UK with only three British specimens recorded. The snag is that its close similarity to S. blackwalli means that other specimens may be overlooked. Thus, I feel morally obliged to check every Scotophaeus I see. Because Mouse Spiders are furry, it's difficult to get a good view of the epigyne without killing them, and as they are so common, that's a problem. Having been sent several Scotophaeus to I.D. today, I have been working on a better way of checking that works on live specimens.


Female Scotophaeus blackwalli

Scotophaeus blackwalli has 3 dorsal spines on femur III & IV (small juveniles may lack the diagnostic distal spine).
Scotophaeus scutulatus has 2 dorsal spines (proximal and median, no distal spine) on femur III & IV.

So telling them apart is "easy" - just look at the spines:


Male Scotophaeus blackwalli: P - proximal spine; M - median spine; D - distal spine (absent in S. scutulatus); S - scutellum (from the Latin for "shield"), an abdominal chitinous plate only present in males - is this for additional protection during mating?


I am indebted to Simeon Indzhov for his patient advice :-)

#LockdownSucksChallenge Round 4 - a couple of noobs

Pocadicnemis pumila

I've finished doing the I.D.s for round 4 (for me) of the #LockdownSucksChallenge. Most of the species are familiar from previous rounds (but a nationwide picture of abundance and phenology will be useful), but there are some changes. Ceratinella brevipes and Pocadicnemis pumila are new for me, and not frequently recorded in VC55 (possibly because of identification difficulty). In addition, my local Pardosa and Xysticus are now (mostly) mature, signalling the start of a mad scramble of the next couple of months.


Pardosa amentata

The full list from this round is:

Bathyphantes gracilis 2m 1f
Ceratinella brevipes 1m 3f
Dicymbium nigrum/brevisetosum agg 1m
Dismodicus bifrons 1f
Erigone dentipalpis 1m 2f
Erigonella hiemalis 5f
Oedothorax fuscus 1f
Pachygnatha degeeri 1m
Pardosa amentata Abundant
Pocadicnemis pumila 1f
Xysticus cristatus 2f

How to improve your microscopy

There's no doubt that microscope optics are important in forming a good image, and if you're going to record the output as a photo or a video, then the capture system and linking optics are important too.  However, I'm increasingly coming round to the view that the lighting is as important as the above.  It doesn't matter if you're using a fancy microscope and an expensive camera or a cheap microscope and holding your mobile phone to the eyepiece to take photos, if the lighting is working against you, then you're going to struggle. Like many people I've been using Ikea Jansjo LED lamps for microscopy. They're relatively cheap and they work OK, but it wasn't until I bought a Brunel Microscopes Dual Flexilite LED unit recently that my eyes were opened:



Using exactly the same optics, the quality of the images I can produce with my kit has improved 10-fold. Here's Dismodicus bifrons, a 2mm-long spider:



And here's the epigyne from this specimen, which is approximately 0.1mm:



I've never been able to produce images this good before. What has changed? Not the optics - only the lighting.

'Tis the season

One of the reasons I like Linyphiidae is because you can find mature specimens all year round. Other very common spiders are often frustrating because they have such short seasons when the are mature and can be identified. In the last week I've had, for the first time this year, mature specimens of Metellina (mengei), Pardosa (pullata), Philodromus, Tetragnatha and Xysticus. It think it's summer. In a normal year this would signal the start of a mad couple of months of recording, before they all go away in the autumn and it's back to Linyphiids for the winter. This year ... who knows?

#LockdownSucksChallenge Round 3 - is that a scapus in your pocket or are you just pleased to see me?

I've just finished checking the I.D.s for #LockdownSucksChallenge Round 3. Mostly this was a repeat of earlier finds, but with the addition of one new species, an old friend:



Bathyphantes gracilis 1m 1f
Dicymbium nigrum/brevisetosum agg 4f
*Diplostyla concolor 1f
Erigone dentipalpis 5m 3f
Erigonella hiemalis 3m 6f
Pachygnatha degeeri 1m

Farewell old friend?

Last year when I was considering which spider species to use a a benchmark for spider recording, I was surprised that the familiar (and easily identified) Garden Spider, Araneus diadematus, was not the best choice (see: Benchmarking Spider Recording, and: Spider Recording in Leicestershire and Rutland). Instead, the money spider Tenuiphantes tenuis was the best fit. While this may be a quirk of the data, it seems that like the familiar House Sparrow, our old friend the facefull-of-spiderweb Araneus diadematus could be on the way out:

"The drastic decline in the abundance of the orb-weaving spider Araneus diadematus over the past half-century documented in this study (Table 1) apparently reveals a bottom-up trophic cascade in response to the widespread insect losses that have occurred across large parts of Europe in recent decades."



Where Have All the Spiders Gone? Observations of a Dramatic Population Density Decline in the Once Very Abundant Garden Spider, Araneus diadematus (Araneae: Araneidae), in the Swiss Midland. https://www.mdpi.com/2075-4450/11/4/248/htm
Aerial web-spinning spiders (including large orb-weavers), as a group, depend almost entirely on flying insects as a food source. The recent widespread loss of flying insects across large parts of western Europe, in terms of both diversity and biomass, can therefore be anticipated to have a drastic negative impact on the survival and abundance of this type of spider. To test the putative importance of such a hitherto neglected trophic cascade, a survey of population densities of the European garden spider Araneus diadematus—a large orb-weaving species—was conducted in the late summer of 2019 at twenty sites in the Swiss midland. The data from this survey were compared with published population densities for this species from the previous century. The study verified the above-mentioned hypothesis that this spider’s present-day overall mean population density has declined alarmingly to densities much lower than can be expected from normal population fluctuations (0.7% of the historical values). Review of other available records suggested that this pattern is widespread and not restricted to this region. In conclusion, the decline of this once so abundant spider in the Swiss midland is evidently revealing a bottom-up trophic cascade in response to the widespread loss of flying insect prey in recent decades.

Upping my game

My standard setup for most microscopy is a stereomicroscope and an LED ring light (switching to a compound microscope if I need to). Stereomicroscopes tend to be optimized for depth of field rather than resolution. Ring lights tend to produce flat images with minimal shadows because the light is directly above the specimen. Put the two together and the images tend to be low contrast and muddy. Adding adjustable low incident angle spot lighting produces controllable shadows and therefore adds to the 3D effect of the image. I'm a big fan of the 10W Ikea Jansjö LED worklamps for supplemental lighting - they're cheap and convenient but they do have a few issues. They are a warm colour (somewhere around 3000 K) and since my ring light is more of a daylight spectrum (around 5000 K), it's difficult to produce images with accurate colour. Second, they have quite a wide angle of incidence and thus tend to produce quite a lot of scatter.

Today I took delivery of a Brunel Microscopes Dual Flexilite LED unit - big shoutout to Brunel, it arrived 48 hours after ordering. It's well made and for a piece of microscope kit, reasonably priced. More importantly, it's bloody good. Using the carefully angled incident light from this unit to supplement the LED ring light (same colour), the resolution is much better than the ring light alone and considerably better than using the Jansjö LED lamps. Sadly, the specimens I pulled out of the freezer to try it out on were both immature, but I'm very happy with the quality of the images.



A juvenile Metellina, which I strongly suspect is M. merianae, but I can't prove it:




(Click for larger images)

Gonatium rubens? Gongylidium rufipes? Hypomma bituberculatum? We'll never know! Don't worry about it and just admire the quality of the image!

(Click for larger image)

Leicestershire LadyBirds A-Poppin

Nephus quadrimaculatus

Over the last couple of weeks the Leicestershire ladybird scene has gone a bit mad (see: NatureSpot Lockdown Challenge - Operation Ladybird). Trying not to be left out, on my daily exercise yesterday I gave the local Ivy a damn good thrashing, and was rewarded with my target species, Nephus quadrimaculatus. The first VC55 record for this species was only a couple of weeks ago, but now they're popping up all over the County, which only goes to show ... seek and ye shall find?

Today I will be mostly processing all the spiders :-)


Rhyzobius chrysomeloides

#LockdownSucksChallenge - Round 2 Results

Following the first round a couple of weeks ago I've finally finished processing the samples from Round 2 (for me) of the #LockdownSucksChallenge. For various reasons, it's taken a week. Scores on the doors:

Bathyphantes gracilis 2f
Dicymbium nigrum/brevisetosum agg 3m 3f
Dicymbium nigrum sensu stricto 1m
Diplocephalus latifrons 1m
Erigone dentipalpis 1m
Erigonella hiemalis 2m 6f
Micrargus herbigradus 1m 2f
Tenuiphantes tenuis 1f
Tenuiphantes zimmermanni 1m
Ozyptila praticola 1i

No analysis at present, just records. Thinking to come later ;-)