An Early Rise from Brood XIX?

During my morning walk in our Chesterfield suburban neighborhood this morning, I found quite a fascinating thing! I ran across several groups of periodical cicadas (Magicicada spp.) that had emerged during the night. I estimate that I found approximately 250 of these large hemipterans without leaving the sidewalk!

An exuviae (shed exoskeleton) of a recently molted periodical cicada (Magicicada spp.)
A pile of periodical cicada (Magicicada spp.) exuviae found on a sidewalk underneath a young maple tree.

I am not quite certain about what exactly is going on here. Our next big emergence of these insects is supposed to occur next season in 2024 – the so-called “Brood XIX.” Brood XIX is composed of four species of periodical cicada (Magicicada tredecim, M. tredecassini, M. tredecula, and M. neotredecim) that all follow the 13 year emergence pattern.

A periodical cicada (Magicicada spp.) nymph. This one is a little behind the others. They usually climb up and fasten themselves to an anchoring place to make their final molt into their adult form during the early night hours.
Ecdysis in action! I wish I had my good camera with me on my walk. This is a periodical cicada (Magicicada spp.) making its final molt and will begin its adult form. It took approximately 13 years to get this far.

Why are we seeing these emerge this year? A couple of possible explanations could account for this. These could be “stragglers,” the term used to describe individuals that emerge in years before or after the bulk of the particular brood. This makes evolutionary sense; if the entire brood emerged all on the same year (emergence of the entire brood within a given location occurs within a couple of weeks) and they are struck with a weather or some other disaster, then this would be a very bad day for the brood. With some individuals emerging a year or two before or after the primary year, then this would obviously be beneficial in hedging their bets.

Here you can see a freshly emerged adult periodical cicada (Magicicada spp.) that is still hanging on to its last shed exuviae.
A newly emerged adult periodical cicada (Magicicada spp.) that has not yet hardened its exoskeleton and developed the dark colors that should come over the next few hours.

Another possible explanation is that this could represent a sub-population of Brood XIX that is on a slightly different schedule and may routinely emerge early. This could be due to differences in climate patterns between this one and what the rest of the brood experiences. Brood XIX covers a large area of the southeastern U.S.

An adult periodical cicada (Magicicada spp.) that is waiting for its new shell to dry.

Or, could this be the result of some differentiation between emergence patterns between the four species that constitutes Brood XIX? I don’t know but I would love to hear any thoughts from those of you who are more educated and experienced in these things than I am. I will be keeping my ears open during the next several weeks with hope of hearing this rare song.

An adult periodical cicada (Magicicada spp.) that has made it to its last stage in life and is getting ready to fly into the treetops to find a mate.

Thanks for stopping by!
Ozark Bill