'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 ;-)

Wild and Wacky (We are the Robots)

When I talked about spider recording in VC55 a couple of months ago, the discussion quickly became "imaginative", and by the end of the meeting, we had "decided" ;-) to equip a drone with an eVac and program it to fly a 10m grid covering the whole of VC55 taking samples. These would need to be sorted by hand to sort out the [insert taxon of choice, e.g. spiders] from the debris, and then sent off for DNA barcoding (High-throughput sequencing for community analysis: the promise of DNA barcoding to uncover diversity, relatedness, abundances and interactions in spider communities (2020) Development Genes and Evolution volume 230, 185–201). Not good news if you're an ecological consultant, great news for gene jockeys.

Mass sampling projects are "easy" to set up. "Hey, I know, let's sequence the whole of Wytham Woods." There was another one published yesterday (Changes in phenology and abundance of suction‐trapped Diptera from a farmland site in the UK over four decades. (2020) Ecol Entomol). What's not easy is processing the data they produce. It took the Danes 15 years to record the results of their malaise traps (The Swedish Malaise Trap Project: A 15 Year Retrospective on a Countrywide Insect Inventory (2020) Biodiversity Data Journal 8: e47255). Right now DNA barcoding is the only feasible way of tackling the mass of data such projects produce. But maybe not for much longer. A.I. (Artificial Intelligence) is coming: A light trap and computer vision system to detect and classify live moths (Lepidoptera) using tracking and deep learning. (2020) bioRxiv https://doi.org/10.1101/2020.03.18.996447, and: Successful launch of automatic insect counting in North Holland. I've been concerned about the impact of A.I. for some time. Well, not about A.I. as such, more about A.S. - the poorly functioning first generation systems - Artificial Stupidity. It's not there yet, but inevitably it will come.

Recently I've noticed a disturbing trend in entomology blog posts to include dodgy music videos. Until the A.I. finally takes over, it seems that We are the Robots: