Το Ημερολόγιο του Pardosa lapidicina group

These got me excited when I first found them at iNat. It was early days in my studies and the images were good quality and numerous. At that time, I had only located one population of lapidicina group spiders myself and was just getting started recording body lengths and ventral views. Now I'm sure enough to do a species ID for them. Although she also observed other Pardosa species, none besides these were in the lapidicina group. Hers are redder than usual, probably as an adaptation to the red rocks in their habitat. You can see a range of appearances. Some have annulated legs, others don't. Some are a lot darker with few markings. This diversity appears typical of most lapidicina group species and obviously makes identification difficult. I've come to believe in identifying them as populations rather than individuals.

Nevertheless, it is possible to find some common characteristics. I've started compiling them and after they are thoroughly tested, I will publish them here. In the matter of lapidicina vs. mercurialis, I'm finding the dorsal color of the trochanter a useful characteristic which shows the importance of good photographs. In addition, I found the dorsal images of specimens preserved in alcohol at BugGuide useful in understanding what I was seeing on the live spiders. Preservation tended to make the hairs transparent so I could see what the surface of the exoskeleton looked like. Hairs get mussed up and knowing what was underneath helped me interpret the patterns better. There were no identified live spider images of mercurialis at BugGuide, so I uploaded a male and a female.

All is not well among the Central Texas lapidicina group spiders. Although most are undoubtably mercurialis, a few I've observed in Bell County don't seem to fit. Going through catherine_g's spiders where there was apparently only one species will help me decide whether they are a different species or not. Pardosa vadosa has been reported in Central Texas, and I always worry about P. sura since there is no trustworthy range or photo for that species.

Identification of species has two faces. It is as important to know what the organism is as what it isn't. Both are required to confidently identify it because we know that some species are easily mistaken for others. Species identification in the Pardosa genus in general and the lapidicina group in particular has long relied on microscopic examination of genitalia rather than general appearance, colors, and patterns. Almost no attention is been given to macroscopic features and it's rare to find a scientific paper with an image of a live spider let alone an array of photos at different stages of development which would be necessary for making reliable macroscopic identifications in the field or in front of the computer.

Using the process of elimination only works if we know what all our options are, and for that we often look at range maps. Looking at the various published maps for the lapidicina group shows a single species, P. lapidicina, standing alone in the eastern half of the county. Since the lapidicina group is relatively easy to recognize from general photographs, it makes for an easy species identification there despite a variety of forms ranging from very pale to brown or black. No lapidicina group species are shown for about half of the eastern states, but looking at observations at iNaturalist shows them in many of those. Clearly, their range hasn't been fully explored. This didn't surprise me since my search for lapidicina group spiders in central Texas showed them numerous in widely scattered locations and rather particular about their habitat. In fact, I had to work pretty hard to find them at all. I eventually decided they were all Pardosa mercurialis.

As I started trying to establish what my local species options were, I noticed there were no lapidicina group observations at iNaturalist from a large block of counties in eastern Texas. It was impossible to know if they were there but had been overlooked so far. I looked in Louisiana and found nothing. I looked in Mississippi and found nothing. At least P. lapidicina was supposed to be there according to the literature. I looked in Alabama and finally found some lapidicina group individuals. P. lapdicina is the only option. The principal form is an attention getter with patches of black and near white in a messy checkerboard pattern. I was able to find similar spiders in other southeastern and mid-atlantic states. By the time I got to New England, the principal forms were drabber and darker. All could reasonably be identified as P. lapidicina since it was the only known option. About this time I noticed my local mercurialis were yellow on top of the trochanter, a short, mostly bare segment at the top of the leg which is often visible in images at iNaturalist. I also noticed that lapdicina was black in the same place. Finally a clue that might help to tell the species apart!

I continued to search westward to the limits of the published range for lapidicina along the eastern slopes of the Rocky Mountains and down to Oklahoma which was supposed to only have mercurialis. Observations at iNaturalist suggest that was generally true. I found some apparent mercurialis farther north comingled with apparent lapidicina. I ran into a problem with the lapidicina group spiders along both sides of the Mississippi River where the principal form was dark brown with muted markings. Spiders which were fairly similar came with either yellow and black trochanters making this clue appear unreliable in the region. Of course, this needs further investigation

Although I originally had lapidicina as one of my local options, my virtual lapidicina tour helped me conclude they weren't in Texas after all and strengthened my species identification of mercurialis.

I photographed 12 lapidicina group spiders near the upper and lower McKinney Falls in Travis County. They were lighter than the ones from Williamson, Milam, and Bell Counties although some from below the upper falls had stronger banding and one was a darker brown. Most others were without gray or black except for the leg bands. However, considering the ranges of appearance of each county group I failed to find any consistent characteristics to indicate more than one species was involved.
Each population was slightly different on average. Those from Williamson had the greatest contrast and variety of colors looking somewhat reminiscent of P. lapidicina in the southeast U.S. Those in Travis tended to be the lightest with the least variety of color. For now it seems all are probably P. mercurialis and the search for P. vadosa will have to move farther west.