Assassin, or innocent bystander?

Last week, we had an assassin bug. So, what’s this one? At first glance, it doesn’t look all that much different from the assassin bug, other than coloration[1]. It even looks like it has a neck. If we look closer, though, there is a key feature that gives it away: the middle section of the hind legs (the tibia) is flattened and enlarged, kind of like a leaf.

This is a feature of “leaf-footed bugs”, (family Coreidae). Looking more closely at the exact shape of the “leaf”, the coloration, the markings on the wings[2],

the eyes,

and the antennae,

I’m pretty sure that it is a Western Conifer Seed Bug, Leptoglossus occidentalis.

These guys are actually a recent arrival in the area. The are native to the West Coast, but according to this article they had expanded their range into Michigan as of the early 1990s.

As an invasive species, this is a bit different than usual. Most invasive species in this area seem to have come from another continent altogether (usually Eurasia)[3]. Leptoglossus occidentalis was in North America all along, and is currently just expanding its range due to changed conditions. And what changed conditions might that be, you ask? Well, it sounds like what happened was that several eastern species of pine trees (Red pine, Eastern White pine, Scots pine) and one European species (Austrian pine) have been introduced in tree plantations in the west. These were all trees that Leptoglossus occidentalis could feed on, and have basically made it possible for them to have a continuous chain of host plants leading all the way across the mountains and great plains to the east.

As for their habits, they overwinter as adults. In the spring, they lay their eggs on immature pinecones, and the nymphs evidently suck juices out of the developing cones and seeds (since they are true bugs, they have the characteristic piercing/sucking mouthparts and so can’t actually chew anything up). They mature by late summer, and then find someplace to overwinter. This often means somebody’s house, which is why we found a couple of them strolling around our bedroom this year in early October.

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[1] As I said last week, I had thought the actual assassin bug we found was a harmless squash bug and handled it very carelessly, only avoiding getting bitten by pure luck. This time, I thought this bug was an assassin bug and handled it with care, and then it turns out it was completely harmless. It figures. Although, maybe not completely harmless; in regards to another bug that only sucks plant juices, Serendith sent me this comment a while back regarding cicadas:

“The long stylet is used to puncture branches (the same way other true bugs do). I have kept them at the museum and they only live if I give them trees that the species likes to feed off of. Beyond that – one “bit” my boss (pierced him is more like it) in what we believe was an investigatory sip … creeped him out and hurt a little but no lasting damage.”

I expect that any bug that can drill a hole in wood to suck sap out, won’t have any trouble with human flesh if they are so inclined. It’s just that they normally aren’t so inclined. Of course, since plant-sap-sucking bugs won’t inject digestive fluids and toxins the way that predatory bugs will, it shouldn’t be as painful as an assassin bug bite.

[2] These wings are a good example of the feature that the true bugs (Hemiptera) are named after. Hemiptera is greek for “Half wing”, and the forewings of true bugs are often hard and opaque in the front portion, and membranous at the ends (the hindwings are tucked under the forewings).

[3] Although, particuarly up here in the Upper Peninsula, the key difference between an “Invasive Species” and a “Native Species” is that the “native” species got here before anybody was keeping records, and the “invasive” species got here afterwards. Given that this was one of the last places in the US that the glaciers pulled out of, nothing has been here longer than 10,000 years, and only a few things have been here as long as 8,000. Some of the trees, like Eastern Hemlock, have only been here about 2000 years. In general, it sounds like this area never did reach a steady-state ecosystem between the melting of the ice and the arrival of the lumberjacks in the 1800s, and certainly didn’t have enough time to evolve much in the way of unique species.