Spotted Cucumber Beetle (Diabrotica undecimpunctata)

Opinion

based on a truly eastern individual:

It is true for the 12 spots, but I´d consider a fusion of the two scutellar spots as of minor importance.
More important would be a difference in antennal and leg colouration - but there is none compared to western ones.

Maybe there are no two subspecies?

… Boris Büche, 29 February, 2008 - 8:38am

Western beetles

What is your opinion on this image?

It seems different from all the rest on this species page.

… Ted Kropiewnicki, 29 February, 2008 - 9:23am

Opinion 2

You are right, this is the only one in which the external spot in row 2 is reduced. In all specimens, it is smaller than the internal one, but both may expand and merge. In all spotted beetles, you can observe variation of this kind.
The colour difference seems to mean nothing, because you can even find tricoloured specimens, e.g.:

One specimen I found in the guide has the antennae completely black, but is from CA.

Still seems the proposed differences between an eastern and western subspecies are not confirmed.

… Boris Büche, 1 March, 2008 - 9:28am

I don't know in this case...

but some experts take their IDs further than others. It may be quite simple to tell one subspecies from another, but someone who doesn't work with a particular group might only know it at the species level without reading up on the subject, or might not consider it important to know what subspecies it is.

It's great when we have an expert who can ID to a particular taxonomic level, but even better (and rarer) when they take the time to explain how they know, and what's needed to reliably make such an ID.

That's not to knock those who don't: given the huge size of the subject, even the most knowledgeable expert is ignorant about some of it, and few have both the expertise in an area and the time to give everything the attention it deserves. This is a volunteer site, so we gratefully accept whatever we can get

***Update***
I looked through the images for the species, and only a handful were IDed by anyone I would classify as an expert. It's apparently an easy ID to genus (maybe even species) level, but I think we just haven't had anyone who knows the subspecies go through the images to see if they can be sorted out.

… Chuck Entz, 10 February, 2008 - 10:48pm

Hi Chuck!

I completely agree with your general points. And thanks for your update and for looking through the images.

After spending too much time looking on the Web, I finally found a reference from the pest managment literature:

http://www.eppo.org/QUARANTINE/insects/Diabrotica_undecimpunctata/DIABUN_ds.pdf

Quote:
"Adult:
Length 6-7.5 mm long. In D. u. undecimpunctata, the abdomen is greenish-yellow with 11 black spots on the elytra (Arnett, 1985), while in D. u. howardi, it is yellow to yellowish-red with 12 large black spots. The head, antennae and legs are entirely black (howardi) or with some greenish-yellow (undecimpunctata)".

After looking through the beetle images with this in mind, I'm still having trouble!

Hopefully an expert will help us out!

In the meantime, it seems inconsistent to have this ONE image, that appears not to have been ID'd by an expert, on a subspecies page...

… Ken Schneider, 11 February, 2008 - 10:32am

Build it and they will come

I used that one image (Photo#150955) to ID another (set of 3) Photo#168819 as D. u. undecimpunctata. I am not an expert of the species but then again all we have is an image not the actual specimen. My ID was based on not just that one image, but on the fact that Eric Eaton created the subspecies page; yes, authoring Kaufman Field Guide (1) does count with me. I do agree that we need more experts to visit Genus Diabrotica as I have seen that all images (except Photo#88388 which has 10 spots) seem to have 12 spots. Nevertheless, every species or subspecies page usually starts with just one image so I am not sure what is the point of the ONE image comment.

Edit: By the way, thanks for the link to EPPO Data Sheets, I added the appropriate information to D. undecimpunctata species page; every bit of information is helpful in the long run.

… Ted Kropiewnicki, 13 February, 2008 - 8:27pm

Eric's an expert

He created the subspecies page. I agree about the inconsistency, though. I suppose the question is whether the potential is there to have many of the images IDed to subspecies, and whether we're conveying any useful information by doing so. I'm not qualified to answer that question

… Chuck Entz, 12 February, 2008 - 7:37am