What Is the Difference Between the Western Conifer Seed Bug & the Shield Bug?

Bugs Have Families, Too

• The western conifer seed bug (Leptiglossus occidentalis) is classified in the Coreidae family, which includes members that are commonly called leaf-footed bugs. Shield bugs encompass different species, but all are in the Pentatomidae family and are commonly called stink bugs. The western conifer seed bug is sometimes mistakenly identified as a stink bug because it shares a common trait with shield bugs -- both types release a malodorous smell when touched. This defense mechanism helps keep predators at bay.

Shapely Little Creatures

• Leaf-footed bugs are aptly named. Their feet or legs are shaped like tiny leaves. Although other family members have pronounced leafy foot or leg structures, the western conifer seed bug has only a slight bulge on its lower hind legs. Shield bugs’ family name, Pentatomidae, hints at a common characteristic of all family members -- a five-sided, shield-shaped body. Unlike their leaf-footed cousins, shield bugs have straight legs. Western conifer seed bugs are brown, but shield bugs may be brown or green.

Favorite Foods

• Both generations of the western conifer seed bug and shield bugs -- nymphs and adults -- feed on plants, although they have different targets. As its name implies, the western conifer seed bug feeds on the flowers and seeds of conifers, such as white pine (Pinus strobus), which grows in U.S. Department of Agriculture plant hardiness zones 3 through 9, and western hemlock (Tsuga heterophylla), which grows in USDA zones 6 through 8. Shield bugs feed on fruits and ornamental flowers, extracting cell sap through their needlelike mouthpieces.

Foreign vs. Domestic

• As a U.S. native, the western conifer seed bug’s range has expanded to the East and into Canada from its original West Coast habitat. Although some shield bug species are U.S. natives, others are immigrants from other countries. The brown marmorated stink bug (Halyomorpha halys) is of particular concern as an invasive, non-native pest. This species may cause substantial crop losses and creates a nuisance when large swarms gather on outside walls and invade homes.