Rainbow Dust [Book Review]

Rainbow Dust: Three Centuries of Delight in British Butterflies
Peter Marren
Vintage, 2016
ISBN: 1784703184

Cover blurb: "Rainbow Dust explores the ways in which butterflies delight and inspire us all, naturalists and non-naturalists alike. Beginning with the author's own experience of hunting and rearing butterflies as a boy, Peter Marren considers the special place of the butterfly in art, literature, advertising and science, and, latterly, our attempts to conserve them. Rainbow Dust takes in the controversy over collecting, the women who studied them and the curious details that lead to butterflies being feared as well as loved. This is a celebration of butterflies; one shot through with a sense of wonder but also of sorrow at what we are losing."

Peter Marren is now a highly respected nature writer best known for the excellent Bugs Britannia and Chasing the Ghost: My Search for all the Wild Flowers of Britain. Although I enjoyed reading Rainbow Dust and learned a lot from it, this is very much in the old school of nature writing, and personally, I enjoyed The Moth Snowstorm more and would recommend that over this book. Nevertheless, Rainbow Dust is still a good read and I recommend it.

Catching the red eye

The glowing red eyes of Drymus brunneus staring back at me from the leaf litter at Charnwood Lodge. It's not as scary as it looks, partly because it's a trick of the light, but mostly because this 4mm long ground bug feeds on mosses and fungi.

Scorpions at Charnwood Lodge?

Neobisium carcinoides

Actually no, but there are pseudoscorpions, related to true scorpions but in a separate Order of arthropods. Like true scorpions they are venomous, but they have venom glands in their chelicerae (pincers) rather than a sting in the tail. The good news is that at only 2-3mm long, they are completely harmless to humans, although not so to the springtails, mites, nematodes and other tiny organisms on which they feed. On a recent trip to Charnwood Lodge I found abundant Neobisium carcinoides in the leaf litter at two different locations. There are more than 3,300 species of pseudoscorpion worldwide, with more being discovered on a regular basis. Most live in leaf litter, moss and soils but some live in houses, such as the Book Scorpion, Chelifer cancroides, which feeds on booklice and so helps to preserve your library!


Charnwood Lodge

Neobisium carcinoides was last recorded at Charnwood Lodge in 1968. Although this species is easily overlooked I am surprised that it has not turned up in the many invertebrate surveys which have been conducted since then. The first County record dates from Buddon Wood in 1929, and John Crocker recorded it regularly on Charnwood in the 1960s. The most recent County record is from Beacon Hill in 2017 but like so many soil arthropods, this is very much a neglected group of organisms and they are undoubtedly widesprerad across the County. Please keep your eyes open for these tiny marvels!

Filling the White Holes

I'm growing increasingly obsessed with data that isn't there... Earlier this month Dom Greaves used the phrase White Holes on Twitter:



It stuck in my mind and I haven't been able to shift it. Previously, I've used R to plot heatmaps of VC55 (Leicestershire and Rutland) spider records (all VC55 spider records (>43k) to end 2018, data copyright Leicestershire and Rutland Environmental Records Centre) (click images for larger versions):



However, the problem with heatmaps is that they inevitably focus attention on where the data is, rather than where it is missing. As an attempt to try to switch the emphasis I tried quadrat mapping - arbitrarily dividing VC55 into a grid and looking at the number of records within each section. Initially I tried a 50x50 grid but with 43,000 records, that choked my computer. A 25x25 grid worked but the the intervals were a bit small and a 10x10 grid is more informative:



Conveniently, R gives the record counts for each tile:



and plotting a histogram of the counts draws attention to how skewed the distribution of records is. Result!



The method isn't prefect. The tiles and hence the counts are of unequal area where they overlap the VC55 boundary, but I don't know how you get around that, with the possible exception that plotting the data by parish rather than by quadrat might be better?

The other place I'm currently stuck is trying to turn unstructured data into occupancy models. This is another White Hole Problem, but one that continues to defeat me.


Acknowledgements:

• All data Copyright Leicestershire and Rutland Environmental Records Centre.
• Data visualization performed using the R platform, v. 3.6.1 (R Core Team (2014) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org).
• J. Cann for assistance with data visualization.

Gnathonarium dentatum

I'm not entirely sure where I'm going with this, but here's my first attempt to combine focus stacking with HDR.

Gnathonarium dentatum.

The "return" of Uloborus plumipes

Uloborus plumipes, also known as the Feather-legged Spider (derived from the Latin pluma "feather" and pes "foot"), or Garden Centre Spider, is a European species now widely distributed in greenhouses and garden centres worldwide. Believed to have been imported from The Netherlands on plants and first recorded in the UK in the 1990's, this species survives in greenhouses and buildings where the winter temperature is maintained above freezing. In this habitat it appears to play an effective role in controlling whitefly, but they are not commonly found in domestic houses. Although it is now widely distributed across the UK, they are cryptic and difficult to spot as they hang upside down motionlessly in their webs. Their horizontal webs and star-shaped egg sacs are much easier to find than the spiders themselves. Females grow up to 6mm and appear to vastly outnumber males, but this may be because the 4mm males are even more cryptic than the females. This species lacks venom glands and traps prey by entanglement in fuzzy, non-sticky cribellate silk.

The Garden Centre Spider was first recorded in VC55 (Leicestershire and Rutland) in 2001, ironically in a garden centre only half a mile from my home. It was subsequently recorded at Brooksby Agricultural College in Melton Mowbray, once more in a now-defunct Leicester garden centre, and finally in the plant section of a Homebase Superstore on 12/06/2006. The species has not been recorded in VC55 since that date, so, with half the roads and fields in the County underwater, I decided to go and do some fieldwork in warm garden centres. The logical place to start was the original location near my home. The only problem with that plan was that this garden centre no longer exists, having been replaced by a housing estate. However, before redevelopment, the owners moved the garden centre business to a new location in the County, so that's where I headed.

It took me approximately three and a half minutes to find the first one, naturally enough, an adult female. Webs were very much in evidence, and after a bit of search, I also managed to find a juvenile. Home again within the hour. One of the good things about being an Arachnologist is that it allows me to predict the future: if the weather stays this wet, more garden centre visits are in store :-)

Diplocephalus latifrons - why the long face?

"Being honest, I'd finished the earwigs and I was bored so I doodled a few crazy spider designs. I think this one looks cool though and I might make it."
God.

Diplocephalus latifrons - why the long face? There's a good reason why some male linyphiids have these wacky cephalic extensions. During mating, the male approaches the female from the front. Most male spiders use the front legs to try to hold up the female or her chelicerae and stop her biting him. In these spiders, the chelicerae fit into the sulcus (groove) on the cephalic hump, wedging them open and preventing her from sinking her fangs into him. But are female spiders really that dumb? No. The sulcus is rich in glandular tissue and the secretions are actually a form of nuptial gift. Matings where females do not receive these nuptial secretions are less likely to result in successful reproduction. Nice design!

Spider Explosion!

click for larger images

Heavy rain (an understatement) during the last week has washed any remaining spiders off the foliage and the action is now all down in the leaf litter. It's been sift-and-sort all the way this week. I've examined leaf litter from four different sites and the number of Microneta viaria has exploded. I have found them as the predominant species at all the sites I have visited, and at one site, they are all I found! This has solved one mystery for me. For the past few months I have been finding immature specimens of a spider with a grey prosoma and orange opisthosoma I have not been able to identify:



It's now clear that these were immature Microneta viaria and now I can see why there were so many of them! Fortunately, they are easy to identify when mature. Both the male palps and female epigyne are characteristic and the prolateral spine on the inside of tibia1 is also helpful.




Epigyne

I think it's no accident that this has coincided with large numbers of springtails in the leaf litter (particularly Dicyrtomina saundersi) - food availability has spurred mass maturation.

How to do biological recording

An interesting new preprint addresses an issue I've been concerned about for a while, how to control for recording effort in assessing how species are doing (Rapid assessment of the suitability of multi-species citizen science datasets for occupancy trend analysis: https://www.biorxiv.org/content/10.1101/813626v1).

The biggest volume of biological data is recorded by unstructured citizen science schemes. Because the data is collected in an essentially random way, many taxon experts are sceptical about the value of these schemes in accurately reflecting populations in the field. Although the statistics are complicated, the method of the new paper seeks to turn unstructured data into occurrence data, i.e. data where we can be sure (to any specified degree) of the presence or absence of a species in a given time period, or the absence of sufficient data to make a determination. The method to do this is to call each 1km grid square a recording site and to count the number of visits each year, one visit constituting one record by any person in a 24 hour period. From this it is possible to calculate the degree of confidence in the occurrence or absence of a species at the site. Ideally (for high confidence) there would be four or more visits from experienced recorders per site per year, but even in the absence of this, the method provides a way of turning the massive amount of unstructured biological recording data available into findings which are easier to interpret and to place confidence limits on.


(click for larger image)

Unsurprisingly, it turns out that butterflies and moths are the runaway winners, the East Midlands performs creditably, and species which get a lot of publicity do better than those for which there are only a handful of experts who can identify them. Nevertheless, if tools could be developed to enable easy utilisation of the method, this would present a valuable way forwards.


(click for larger image)


Note: R package "unmarked" is of relevance: https://cran.r-project.org/web/packages/unmarked/index.html