Royal Alberta Museum: Invertebrate Zoology - Bug Facts

[Caterpillars and Other Immature Insects]

Fact Sheets: Commonly Observed and Asked About Insects and Spiders Found in Alberta

Western Conifer Seed Bug (Leptoglossus occidentalis)

Western Conifer Seed Bug
Credit: Terry Thormin

INTRODUCTION

Unfortunately this rather attractive bug can be a pest at times, getting into the cracks of houses in the fall and eventually making its way inside the house.

IDENTIFICATION

By Alberta standards this is a large insect, getting up to about 1.9 cm long. The shape is like a somewhat elongated shield with a prominent head with long antennae sticking out the front end. The second obvious joint (tibia) of the hind legs is expanded into leaf-like plates towards the tip. It is this characteristic that gives the family (Coreidae) the common name of leaf-footed bugs. The mottled brown colour of this insect probably allows it to hide effectively on the branches of trees. In flight, the abdomen is yellow with five thin black bands. This, combined with a buzzing sound given in flight, might cause it to be mistaken for a bee or wasp.

DISTRIBUTION

This insect was originally distributed in the western half of North America, but in the last few decades it has gradually moved east across the northern United States into northeastern United States and southern Canada. In Alberta it is restricted to the southwestern corner of the province around Waterton Lakes National Park and Crowsnest Pass.

TIME OF YEAR

Adults can be found almost year-round. Because they over-winter as adults, and often do so in cracks in buildings, they occasionally turn up indoors during the winter months.

HABITAT AND HABITS

This is an insect of conifers, showing a preference for inflorescences, seeds and first-year cones of Douglas Fir, White Spruce, Hemlock and various pines. Over-wintering adults emerge from late May to mid-June and lay their eggs shortly after. The eggs take about 10 days to hatch. By mid-August the first of the new adults can be found. In the late summer and fall, adults will start to look for places to spend the winter. Normal places are under the bark of conifers, and in hawk and rodent nests, but houses have become one of the main over-wintering habitats.

SIMILAR SPECIES

In Alberta, this is the only leaf-footed bug with expansions on the hind legs. In eastern North America, the Leaf-footed Pine Seed Bug (Leptoglossus corculus) could be mistaken for the Western Conifer Seed Bug, but it has a predominantly black upper surface to the abdomen

COMMENTS

Western Conifer Seed Bugs can significantly reduce seed crops in some conifers. This can be a serious problem in some tree nurseries. Most people, however, are concerned about the numbers that collect on their houses in the fall, and the ones that turn up inside in the middle of the winter. The best advice we can give is to fill in any holes around windows and doorframes to prevent the bugs from getting in, and to regularly spray any bugs that get on the house walls with a blast of cold water. Any that do make their way inside should just be removed by hand.

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Last update: October 22 2004