Insect Catch-Up

by Carl Strang

I consider photos to be an indispensible part of this blog. Blogs are based on writing, but in a visual medium like a computer screen, I believe images are needed as well. I try to get photos of everything new I encounter in the field, and edit and copy selected ones into a file I keep for the blog. They then are the basis for new posts. Sometimes there are orphan photos, ones which by themselves may not be enough for an entire entry. Today I want to clear out three such photos of insects. The first goes back to mid-June.

Unicorn clubtail on May’s Lake

I had been seeing a few jade clubtails at Mayslake Forest Preserve, perched on shore or occasionally on floating algae, but then on June 16 there was an odd-looking individual that clearly was a new species for the preserve list. The photo made clear that this was a unicorn clubtail, a species in the same genus as the jade clubtail, common in some places but not, in my experience at least, in DuPage County.

Reversed haploa, a member of the tiger moth family

This was a big year for reversed haploas. Usually I see 5 or so in a season, but I saw dozens at Mayslake in the first half of July.

Bombus pensylvanicus. I think.

There are two species of bumblebees in northern Illinois that are so similar I cannot distinguish them confidently. From what I have seen in internet sources, I am not alone in this. Both have large areas of black on the thorax and large areas of yellow on the abdomen. There are variations in “fur” color on the head and posterior thorax that bring enough overlap into the picture to confound the identification of individuals. As far as I can tell, it comes down to the color of the basal abdominal segments. Less black and more yellow indicates pensylvanicus, more black and less yellow indicates Bombus auricomus. In my limited experience, though, there appears to be another possible indicator. B. auricomus seem to be brighter, the yellow and black so sharp as to really stand out, while the colors are duller in pensylvanicus.

Here is an auricomus from an earlier year

If any readers can lend insight on this, I would appreciate a comment to that affect.


Progress on Bumblebees

by Carl Strang

Earlier I posted some background on bumblebees . I find that I made an error or two there, I since have found additional species at Mayslake Forest Preserve, and also some added web sites specific to Illinois bumblebees that have helped immensely. The total list for Mayslake at this point includes 5 species, and I showed a photo from Fullersburg Woods of a 6th, Bombus vagans, in that earlier post. There are 9 species total for Illinois, of which 2 are rare. (Here I am not counting the nest-parasite “cuckoo bumblebees,” of which there are 2, but which I have not yet encountered). To this point in the season, the most common species has been Bombus bimaculatus, both at Mayslake and in my garden at home. It has a yellow thorax except for a black dot on top, the first (basal) abdominal segment is yellow, the second segment is yellow in the center front edge but black on the ends and back edge. Otherwise the abdomen is black.

Bombus bimaculatus 2b

The patch of yellow on the second segment often is small and hidden by the wings, so care is needed to distinguish bimaculatus from another common species (though perhaps less common locally than I implied in that earlier post), Bombus impatiens. The main difference from bimaculatus is that the yellow on impatiens’ abdomen is confined to the first segment.

Bombus impatiens queen 2b

One correction I need to make to that earlier post is that the dead bumblebee I featured was not Bombus fervidus after all. That bee had a black basal abdominal segment, where in fervidus the first 4 segments all are yellow. I have found a few live members of the dead bee’s species at Mayslake.

Bombus auricomus 10b

This is Bombus auricomus, which is regarded as “uncommon” in Illinois. Here, the first segment is entirely black, segments 2 and 3 entirely yellow. The sides of the thorax are black, and as the next photo shows, there is a large black area in the center of the dorsal (top) thorax.

Bombus auricomus 2b

At Mayslake I have seen only a few of these, always in the same place, so I believe there is only one colony of them on the preserve. Compared to other bumblebees they are large and very active. Bombus fervidus is at Mayslake, too.

Bombus fervidus 3b

Here you can see that the basal segment also is yellow, as is the entire thorax except for a black band across the back between the wings. In that earlier post I mentioned the ecological significance of differences in tongue lengths among species. Get a load of the tongue length on that fervidus!

Bombus fervidus tongue b

The 5th Mayslake species to date is Bombus griseocollis.

Bombus griseocollis swamp milkweed 3b

In this one the forward edge of the second abdominal segment is orange, but the back edge is black. The color on the second segment extends closer to the edge than it did in bimaculatus.

Bombus vagans, which I have seen at Fullersburg but not yet at Mayslake, has the first two abdominal segments yellow all the way to the back edge.

Bombus vagans 1b

That leaves only one species of bumblebee which is said to be common in Illinois but which I have not yet observed: Bombus pensylvanicus (listed in some references as B. americanorum). That one is most similar to B. auricomus, but typically has the top rear part of the thorax black or orange, and the first abdominal segment has some yellow on its rear edge.

Here are some web references. For a really nice diagrammatic comparison of these color patterns you can download a pdf file called “Bumble Bees of Illinois and Missouri”. A site with additional identification and ecological information is the beespotter site.

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