A December Surprise and Mystery Moth
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It has been a rather warm winter at Harmony Hill and, even with some chilly nights, the days have been sunny and very pleasant. Shortly after sunrise, the radiant heat of the sun brings the temperatures up and we often bask in that lovely yellow glow. Just as we have enjoyed the warm days extending towards the end of the year, it is clear we aren’t the only ones in the forests taking advantage of the delightful rays. Turtles sit on logs in the creek, birds flit around during the shortened days and we’ve even seen dragonflies darting around as they hunt. Reptiles and birds aren’t unexpected as we prepare to turn the calendar, but the levels of insect activity we’ve seen is a bit of a surprise.
It is true that we never truly get cold at Harmony Hill, especially when compared to the northeast, upper Midwest, and Rocky Mountains. We rarely see snow and single digit temperatures are unheard of here. However, we’ve typically seen a few hard frosts by now and insect activity is usually diminished. This December has been different and one morning, we were quite surprised to find an insect well outside of the timeframe it would be expected.
Not only are we going to talk about an observation that was unexpected, but we’re also going to look at a genus of insects we know very little about. You see, there’s still magic out there in nature and we aren’t even close to knowing all the answers to many of the mysteries she holds close to her vest.
There are places in the forests of Harmony Hill where Eastern Red Cedars (Juniperus virginiana) grow in small stands. The beautiful, deep green backdrop provided by these evergreen trees is a welcome scene this time of year. Most of our oaks, hickories, ashes, and dogwoods have dropped their leaves for the season; and the majority of the pines here are tall enough that they hold their needles well above our heads. But the cedars bring their emerald curtain limbs and needles low to the ground. It was against that verdant screen that a bright yellow spot caught our eye.
Walking towards that contrast in hue, we began to smile as we realized it was not a dead leaf, but a moth that grabbed our attention. And this moth was a couple of months beyond when we would normally see it on the wing.
Geometer Moths (Family Geometridae) are not as vivid as some species of moths, such as Regal Moth (Citheronia regalis) or Luna Moth (Actias luna); nor do they fly with the flair of their Sphinx Moth (Sphingidae) relatives. But they have a subdued beauty all their own and, believe it or not, they are one of the first moths you learn about as a child.
You see, the word “geometer” translates to “earth measurer” and that is one incredibly fitting name for their caterpillars. The diminutive inch worms we encounter as children, of which there are thousands of species, eventually metamorphize into geometer moths!
There are many superstitions associated with the caterpillars for geometer moths. It was believed they measured the ground as they inched along, giving them their name of “earth measurer”. One particularly morbid old wives’ tales even said that, should you see an inch worm crawling on you, it is measuring you for your coffin!
Have no fear. There is no evidence, whatsoever, that this is at all true!
One thing all geometer moths have in common, regardless of species or location, is a fairly cryptic coloration and pattern meant to blend into their surroundings. That slight camouflage can be seen in the photo of our moth. The brownish spots are irregular and break up the line of sight of a potential predator. In fact, when perched against dead leaves, the moth can be nearly invisible. That is something we see regularly in the Lepidoptera Order of insects, which includes butterflies and moths. (Lepidoptera translates to scale-wing. Ever handle a butterfly or moth and notice a dusty residue on your fingers? That is the scales from their wings and, if enough of those scales are lost or damaged, they can lose the ability to fly.)
Now, in all of this, you’ll notice we have yet to tell you which species this moth is. That’s because we aren’t entirely sure! The best we can do is offer you the two most likely species it might be! Part of being a good naturalist is to admit when you don’t know something and to embrace the unknowns in nature. You see, we don’t have to go to tropical rainforests, distant islands, or faraway locations to find mysteries in nature. Today, we embrace one of these mysteries.
This moth is either the False Crocus Geometer (Xanthotype urticaria) or the true Crocus Geometer Moth (Xanthotype sospeta). We can’t be sure! They look identical, fly exactly the same way, and are found in the same habitats! They’re even genetically the same!
Without dissecting this moth and looking at very specific and intricate differences in genitalia, there’s very little we can do to differentiate the two. Perhaps, if we were lucky enough to find the caterpillar feeding on one of the few host plants that doesn’t overlap between the two species, we could more readily identify exactly which we observed. The fact of the matter is, we don’t have the equipment to effectively dissect and study the genitalia and we didn’t see the caterpillar on a plant that might clue us in. Therefore, we share the excitement of not being certain! And we encourage you to get excited about what is yet to be discovered as absolute!
It is likely that the caterpillar of this moth may have fed on the leaves of goldenrod (Solidago sp.) or dogwood (Cornus sp.) at Harmony Hill. But, we have yet to document the caterpillar of either specie feeding here, yet.
Finally, we mentioned earlier that we were shocked to see this moth flying around in December. The latest we have observed this genus of moth on the wing was mid-October, and that was considered later than normal. The usual flight for these moths is from April to September; so, seeing it in December was both an unexpected delight and quite a surprise. It could be that these later observations will become the new normal, as climate change pushes warmer temperatures later into the winter and much earlier in the spring at Harmony Hill.
This is where our walks in forests and fields become more important, not just for our mental health; but, for understanding the current state of natural history for our area. What a wonderful thing! To clear our minds and expand our understanding of nature, all in the act of being out in our wonderful Harmony Hill.