11 July 2026

An Uncertainty of Species

Two English moths are said to resemble each other more than most: the Rustic (Hoplodrina blanda) and the Uncertain (Hoplodrina alsines). The latter is even named after this confusion! For the past three traps, we’ve had plenty of the slightly rougher and more robust Uncertain, but this week I finally found what looks like the Rustic.

With an only marginally slimmer shape and less defined crosslines, I couldn’t be sure of the identification. I sent photos over to Dr. Fletcher (our moth consultant) who confirmed it looked like a Rustic, but acknowledged that it’s hard to tell with certainty. It’s often down to dissection to identify for certain, for which I am not qualified, so I’m tentatively putting it on the list as a new species!

There isn’t a specific reason for this likeness apart from a very recent common ancestor. They have the same taste for herbaceous plants, but the Uncertain emerges for flight a little earlier. This could be the cause of their genetic divergence, called sympatric speciation: when two populations aren’t geographically isolated but begin to reproduce on different timelines, which prevents intermixing between the groups.

Appearances are often deceptive when it comes to genetic similarity. Two moths can look alike despite being distinct species, while other species can have dozens of diverse color forms that share the same DNA!

This wasn’t the only confusing moth in our trap this week. A lacy white and brown striped specimen was first identified by my phone as the Small Engrailed (Ectropis crepuscularia), but after consulting the guidebook I realised it also looked a lot like the Engrailed (Ectropis bistortata). I emailed another photo to Dr. Fletcher, who informed me that the two are not considered separate species anymore.  The drama of naming and un–naming species seems almost as complex as the insects themselves!

Though last week seemed to be the reign of the micro-moths, this week the macros have come back in full swing. I’ve been waiting for my first meeting with a Hawk moth, and it finally came to fruition in this trap: we had six of the Sci-Fi–movie–ready Poplar Hawk Moth (Laothoe populi) and one brilliantly pink and olive green Elephant Hawk Moth (Deilephila elpenor).

Hawk Moths are named, evidently, for their size (they can have wingspans of up to 5 inches!), but also for their fast flight and quick mid–air manoeuvres. The Poplar Hawk Moth is England’s most common, and has been recently expanding northward. As its name suggests, its larvae feed on Poplars but has also been seen on Willow and Sallow trees. The adults, however, have reduced proboscises and can’t feed as adults. They rely instead on the fat they built up as larvae for the few weeks they fly.

The Elephant Hawk Moth is actually named after three different animals: other than the two in its common name, elpenor refers to a friend of Odysseus who was turned into a pig by Circe. Apparently Linnaeus thought the larval heads looked very snout–like.

The larvae of the Elephant Hawk Moth are just as striking as the adults: huge and green or dark brown, they have trunk–like projections and eye markings on their heads. Though mostly nocturnal, my guidebook says they’ve been known to come out and sun on warm afternoons. They’re generally limited to one summer generation, but in some places have been managing two as temperatures rise. The adults are also important pollinators and feed on the nectar of Honeysuckle and other tubular flowers.

As we released this batch at the end of the day, I came across one moth I had somehow missed earlier. With its striking white, blush and brown splotches, the Peach Blossom (Thyatira batis) looks like it’s just flown out of a modern art museum. I was almost incredulous that someone hadn’t painted them on just to mess with us. I was also mildly disappointed when I looked up its scientific name and found that batis only means bramble, its foodplant. It’s a beautiful word, but maybe Linnaeus could have come up with something a little more descriptive? Either way, I was glad to see this one before it flitted off.

Post by Sarah Leonard (UPenn intern 2026)