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

Sidewalk Carabid (Pterostichus melanarius)

Sidewalk Carabid
Credit: Terry Thormin

INTRODUCTION

The Sidewalk Carabid is a ground beetle, a member of the family Carabidae which has almost 400 species in Alberta alone. The Sidewalk Carabid was chosen to represent the family simply because it is the most commonly encountered species in residential areas.

IDENTIFICATION

Ground beetles range in size from about 2 mm to 25 mm. Most tend to be black, but there are a wide variety of colours represented in the various species. Some iridescence is fairly common. The Sidewalk carabid is all shiny black and about 15 mm long. These are robust beetles with proportionately large powerful jaws.

DISTRIBUTION

Ground beetles are found everywhere in the province, and throughout the world for that matter. The Sidewalk Carabid is largely restricted to the larger towns and cities in Alberta, but is gradually working its way into the surrounding countryside. It is an introduced species, originally coming from Europe.

TIME OF YEAR

Because the adults are long lived, this species is found throughout the summer, as are many of the ground beetles.

HABITAT AND HABITS

The Sidewalk Carabid frequents urban areas, often hiding under rocks and stones. At times, when it is wandering around, it takes the path of least resistance down a sidewalk. Like all ground beetles it is a predator, and is beneficial as it eats many insect pests. Most ground beetles move fairly quickly and it is not uncommon for them to get into homes, either by sneaking in a door or finding a crack in the foundation.

SIMILAR SPECIES

With so many species to chose from, one might think that it might be a hard decision, but there are two species that do stand out. The Purple-rimmed Carabus (Pterostichus melanarius) is a large species (up to 23 mm) with an iridescent purple edge to the elytra (front wings) and the pronotum (area behind the head). The Fiery Hunter (Calosoma calidum) is about as large as the Purple-rimmed Carabus, but has a series of small pits in rows on the elytra. These pits are usually coloured iridescent red, but may be gold or green.

COMMENTS

People are often concerned when these beetles get into the house. Remember that these are predatory beetles and as a result are the good guys. Most houses probably do not have enough invertebrates to keep a ground beetle alive, and it is usually best just to move the beetle outside.

For more information on the Sidewalk Carabid you can visit the University of Alberta’s entomology collection species page.

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Last update: December 10 2004