2014 June 18

While the firefly species that actually light up[1] are kind of scarce around Houghton, they do exist. Here’s one that Rosie caught for me during the day, presumably while it was resting after an exhausting night of flashing lights [2].

As we can clearly see here, “fireflies” are actually beetles.

The light-emitting organ on the end of the abdomen is pretty clearly visible. I couldn’t get it to flash for us, but it does look as if the abdomen tip might be faintly glowing all the time.

It’s got pretty big eyes, which can tuck under the shield-shaped pronotum just behind the head. The big eyes suggest that he needs to see well to track down the flashes that a female makes in response to his flash.

After going through the pictures, I’m going to stick my neck out and say that I think he looks like Pyroactomena borealis, a common cold-climate species along the eastern part of the US/Canada border. But, I’ll get back to the difficulties in identifying fireflies to species later on this page.

Downstate, they are much more plentiful. When we went down to visit Sandy’s parents (in Manchester, a small town in the Lower Peninsula that is somewhat famous for their annual Chicken Broil), Sam and I went out into their yard after sunset, and there were fireflies flashing all over the place.

These are evidently a different species than the one from Houghton, as they have much more pink on their pronotal shield. This first one was pretty long, with the abdomen projecting quite a bit beyond the length of the wing covers:

Given her size, this is probably a female. Generally, the male fireflies do the flying, and the females just hang out in the grass and answer their flashes, so the females are not as strong of fliers (and, in some firefly species, the females may not even have functional wings).

The other was smaller, with the abdomen completely tucked under the wing covers:

And in fact, there might have been multiple species of fireflies all out at the same time. This next one looks a bit paler:

In any case, the Manchester fireflies all had three body segments devoted to the light organ:

This is in contrast to the Houghton firefly, where if we scroll up, it looks like it only had a 2-segment light organ, with the final segment being dark.

So anyway, fireflies are in the family Lampyridae, but are pretty hard to identify to species. Or sometimes even to genus. I think the Manchester fireflies are probably all in the Photinus genus, but to go any further, we run into a problem. See, these all look pretty similar, because they didn’t speciate by their appearance. What happens with fireflies, is a particular species will attract a mate by flashing with a characteristic pattern of flashes and delays. It is therefore easy for a lineage of fireflies to develop a particlar flash pattern, until next thing you know they are no longer interbreeding with the rest of the population, and voila! New species! But, the only observable difference between the species often ends up being that flashing pattern, and so when you actually have one in your hand, it is simply not practical to identify it to species.

As a result, BugGuide says that the genus Photinus alone has at least 50 species in North America (some that are still waiting for names), and probably many more that haven’t been identified yet. And the genus Photuris (which is notorious for the females using their flash pattern to lure in Photinus males so that they can eat them) has probably another 50 species. And then there are around a dozen other firefly genera. Then again, from our perspective, the various firefly species are mostly interchangeable. They all have glowing, predatory larvae that live in the leaf litter, and adults that fly at night and flash prettily.

There used to be a market for fireflies. Back around 1984, I had a copy of the Sigma Chemicals catalog, and it had a section describing how to participate in their youth organization, the “Sigma Fireflies”. The idea was that kids would go out and catch fireflies, bring them to a central receiving area, and get paid for them. Sigma would then extract the light-emitting chemicals from the fireflies for various esoteric (and, at the time, very expensive) biochemical applications. Of course, now that we have methods for making the chemicals synthetically, there is no longer a market for wild-caught fireflies. So kids only chase them for amusement once more.

Incidentally, catching fireflies with your bare hands is pretty difficult (they are easy to squash), with a wide-mouth jar is fairly easy (although the ones you already have will tend to get away while you are stalking another), and with an insect net is trivial (although you still need the jar to transfer them to). The basic issue is that you see the flash, and then have to pounce before the afterglow fades and you lose them.

[1] Not all firefly species light up. For example, we have quite a number of these day-flying, non-luminous “fireflies”, which I posted about previously. They are easy to catch when they are mating.

[2] We’ve got two problems when hunting for fireflies up here in the Keeweenaw. First, fireflies are warm-weather insects, and we really don’t get all that many warm nights for them to fly. Second, we are in the wrong time zone (something I have ranted about here in the past). Which means that for most of the summer, it doesn’t get dark enough to see fireflies flashing until sometime around 10:30 or 11:00. This is way too late to expect little girls to stay up. Or their daddy, for that matter.

2 Responses
  1. June 18, 2014

    Amazing! No, not the photos or the text, both of which were fabulous, but the fact that you could find someone from Manchester scoring during the World Cup.

  2. June 18, 2014

    LOL, K T Cat! Our fireflies are 10 days late (bordering Milwaukee, WI), much to the consternation of neighbors who have houseguests from Spain who have never seen any. I unwisely sent out an email last night predicting they’d be out then or tonight, but the temps dropped into the 50s. I just checked. Still no fireflies. Maybe I can’t see them because they’re still wearing fleece like the rest of us?

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