Adolescent Spiders

This was something I was meaning to check out for some time. I'd noticed a peri-adult molt in both Hogna and Pardosa mercurialis. Many of the earlier pattern change are lost during this molt and sexual dimorphism becomes more pronounced. I suspected this wasn't coincident with sexual maturity, and here's the proof:

https://www.inaturalist.org/observations/99620141
https://www.inaturalist.org/observations/90292781

Both are egg sac bearing mercurialis. The first one has the earlier pattern. Although faint in this individual, the pattern around the outside of the thorax consists of a pale band with a dark edge and a couple of dark partitions. The band isn't perfectly even and bulges inward in two places. At least P. lapidicina and vadosa are very similar. In the second one, the band has lost the dark edging and the two dark partitions are replaced with dark darts which point inward. Remember that these patterns are from hairs so sharpness can vary.

So, a good series of photos for species like this would include:

1. juvenile forms, multiple, approximate age determined by size
   (sexual maturity occurs between 1 and 2)

2. adolescent form with juvenile-like pattern and limited sexual dimorphism, near adult size
3. adult form of each sex plus other forms like chocolate and black in mercurialis

It may be reasonable to disregard sex in the juvenile and possibly adolescent forms.

About a dozen sets of images would be needed to thoroughly cover the patterns of mercurialis for field identification of a population.

No wonder field identification of wolf spiders scares most people. Even Barnes, 1959, steers clear of the issue with statements like "Structure and coloration are typical." for mercurialis and "Coloration typical, although most specimens are light brown in color. Sternum pale or dusky. Structure typical." for vadosa, a new species he was introducing.

Posted on 20 December, 2021 12:28 by eaneubauer