I have a rather large population of these guys around my place and I finally decided to submit at least some of the photos I've taken and try to nail down a few IDs. On initially reading the 1957 Bulletin of the CA Insect Survey (PDF) (which I know you are familiar with), I too came to the same conclusions regarding possible species. However, a few things have caused me to wonder a bit...

1) I thought, considering it's also an introduced species, that it might be plausible that Oligotoma saundersii has now made its way to CA. (There's a record on this site from AZ, which isn't too far away...)

2) The aforementioned PDF states that Oligotoma nigra juveniles are pale tan and adult females are blackish-brown. However, I was perplexed in coming across this post which claims to show a male and female Oligotoma nigra side-by-side:



The thing is that the female in the above image looks remarkably like those specimens (including my own) that I would have assumed were Haploembia solieri. So.... I guess I still have a bit of doubt as to how to correctly ID my submissions. I am hoping that Stanley Dean Rider will comment on these images, as he has provided clarification for a large number of our webspinner posts.

Very nice images of the embiids posted here. The four wingless specimens you have posted look very much like H. solieri and the winged males look like O. nigra. It is nice to have the male abdominal termini to examine and help in the determination.

It's great to finally start to put some more specific names to all the webspinners around my place!

For my own education, can you offer any insight into how one would tell the difference between an H. solieri female and the O. nigra female shown in the above thumbnail? They look awfully similar to my untrained eye...

You mentioned the similarities between females of different species. Without any other information, it boils down to whether or not you see distinct markings on the body in order to separate out H. solieri. H. solieri happens to have fairly distinct markings on a pale background. These markings appear on the head in what resembles cartoon-like flames, and patterning continues along the entire dorsal surface of the body as bilaterally symmetric maculations. If you examine females of O. nigra, O. saundersii and probably others with strong lighting, you can also faintly see similar flames on the head, but the background color is also nearly as dark. Other than that, females for O. nigra and O. saundersii don't have too much in the way of distinguishable markings. Another female that has distinguishable markings is Anisembia texana. All members of that species have prominent white bands on the mesothorax, which makes them fairly easy to identify in the field even as females or immatures.

I really appreciate you getting back to me on this question, Dean! Your response gives me a much clearer idea of what to look for in the field and while taking photographs. As there is a very large population of O. nigra around my property, I'd like to be able to document some females in addition to the many males I have recorded. I will definitely keep looking, however I wonder why so many H. solieri females and O. nigra males end up in the swimming pool, but I've yet to find a single O. nigra female? Perhaps the answer lies in Chuck's earlier comment where he proposed that the H. solieri colony might be within "walking distance of the pool", while the O. nigra colony is further away. Or, perhaps they're females are just smart enough to stay out of the pool... :-)