Western Conifer Seed Bug Nymph (Leptoglossus occidentalis), A True Stink Bug

Western conifer seed bug nymph (Leptoglossus occidentalis)
Photo by Brad Sylvester. Copyright 2011. Do not copy.

When is a bug not a true bug? When it doesn't belong to the suborder Heteroptera (True Bugs). To qualify as a true bug, there are eleven basic criteria according to bugguide.net. (Nine really, with two more that apply only to some groups of true bugs.)

1. True bugs do not pupate. They change into adult stage gradually with successive molts.
2. Nymphs may have different coloration and much smaller wings, but otherwise look pretty much like adults of the same species. The wings often get larger with each instar stage.
3. True bugs often have a flattened body
4. Wings are beetle-like, but fore-wings may be partly thickened and partly membranous.
5. Hind-wings are membranous and used for flight (as in beetles which are NOT true bugs).
6. When folded at rest, wing-tips overlap or cross.
7. True bugs (and some beetles) have a prominent scutellum (triangle-shaped part of the thorax between the wings).
8. Mouth is beak-like and made for sucking.
9. Antennae have 4-5 segments.
10. *Some true bugs have simple eyes (as opposed to compound eyes)
11. *Some true bugs (including the western conifer seed bug) have defensive scent glands.

Adult Western Conifer Seed Bug: note the overlapping wings,
four antenna segments, and prominent scutellum that are
indicators of a true bug. Also note the leaf-shaped extensions
on the rear legs that make this a leaf-footed bug.
Photo by Brad Sylvester. Copyright 2012

As you can see, true bugs share some traits with beetles and many somewhat resemble beetles. If you are trying to identify an insect that you think is a beetle, but it doesn't match any that you can find, consider that it might be a true bug (Heteroptera) instead.

All of which brings us to today's find: the western conifer seed bug. This true bug was particularly difficult to identify (for me), because most guides use only pictures of the adult form and while this immature specimen is similar to the adult, the differences are enough to cause problems and, of course, I started out with beetles instead of true bugs.

Finally, I figured out that this was a nymphal form of a true bug, and from there arrived at a juvenile western conifer seed bug (Leptoglossus occidentalis). Notice that it has full wings (lacking in my specimen) and a longer, narrower body, but is otherwise quite similar. Once I had arrived at this species, I could confirm the species' presence in my yard by the adult's typical behavior and my previous observations. (Note: I added the adult photo which I took in my yard on October 20, 2012). You see, the western conifer seed bug likes to spend the winter indoors, in human houses. It doesn't breed, burrow, or eat in the house, but just likes to be indoors to stay warm in the winter. In the winter it isn't unusual for an adult specimen of the western conifer seed bug to buzz down from the rafters of my house.

Quick facts about the western conifer seed bug:


Leptoglossus occidentalis, an invasive species in New England
Photo by Brad Sylvester. Copyright 2011. Do not copy.

Range: The range of the western conifer seed bug, according to the Connecticut State Agricultural Experiment Station website, has expanded to the northeast United States only as of the mid-1980's making it an invasive species, but one that migrated here naturally over time from the West.

When is it here? The western conifer seed bug resides here year-round, over-wintering in the adult form. However, it prefers to overwinter inside human houses for protection from the winter cold. This insect may be a case of an invasive species whose continued existence here relies on human help. Although it is possible that it might be able to survive the cold under pine bark.

Diet: Leptoglossus occidentalis sucks plant juices from many species of evergreen seeds, green cones and, less often, needles.

Habitat: Pine forests.

Lifecycle: Eggs are laid in spring on pine needles. Once hatched, Leptoglossus occidentalis molts through five instar stages before reaching adulthood around August.

Lifespan: Unknown

Other facts: As mentioned above, the western conifer seed bug is one of the true bugs that has scent glands for defense. If you crush these bugs in the home, they may give off an unpleasant odor. They are sometimes called "stink bugs."

Taxonomy of the Western conifer seed bug:

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Family: Coreidae
Genus: Leptoglossus
Species: Leptoglossus occidentalis