THE COCKROACHES (ORDER BLATTODEA) OF BRITISH COLUMBIA

by

R. A. Cannings and G. G. E. Scudder
Copyright © 2005 - All rights reserved

Introduction

Cockroaches are ancient insects; they were a dominant group in the late Palaeozoic Era. They are primarily tropical or subtropical in distribution and live under logs and bark, in caves and burrows in the soil, in mammal nests and human habitations and high in trees. There are about 3500 species worldwide; three families, five genera and six species of cockroaches live in British Columbia. All our species have been introduced from elsewhere through commerce or have escaped from laboratory cultures; none live freely outside buildings except, perhaps, Blattella germanica (Linnaeus), which can survive in refuse heaps in the climate of the south coast.

In addition to these species, all apparently well established, seven others have been recorded, but do not have viable wild populations. Four of these are mentioned in the relevant family treatments below; two families are represented in addition to those containing established species: Epilampridae (Epilampra maya Rehn and Nauclidas rufipes (Brunner von Wattenwyl)) and Nyctiboridae (Nyctibora noctivaga (P.de B.)). Cryptocercus punctulatus Scudder, an American species, is of particular evolutionary interest. It lives in colonies in rotten logs where it feeds on decaying wood with the help of cellulose-digesting protozoa, similar to those in primitive termites. In addition, Cryptocercus colonies share another significant termite characteristic – they consist of several generations of a family group and show simple social organization.

In general, cockroaches prefer dark, humid habitats and many are nocturnal, hiding in cracks and crevices during the day. Species that have become cosmopolitan pests find suitable semitropical conditions and abundant food in all sorts of buildings in temperate and even arctic climates and thrive there throughout the year. Blattella germanica lives in heated buildings at Alert on Ellesmere Island, only 750 kilometres from the North Pole. They are omnivorous, but seldom predatory. Usually 15 to 40 eggs are assembled in an egg chamber where secretions stick them together in a capsule or ootheca similar to that of the mantids. The ootheca is formed over several days and may be deposited soon after it is formed or is carried by the female for days. In some species, the eggs hatch in the egg chamber. A female produces several oothecae in a lifetime. Pestiferous cockroaches contaminate food and produce unpleasant odours, although none is implicated in transmitting human disease. These few species have become symbols of unsanitary conditions and are not representative of the order as a whole. Humans go to great effort and expense to eradicate them from their dwellings and storehouses; many populations are resistant to pesticides.

Description

Cockroaches are oval, flattened insects, the adults of various species ranging in length from a few millimetres to 10 centimetres. They have long, thread-like antennae and chewing mouthparts; the head is often concealed below the large, shield-like prothorax. Compound eyes are normally well developed (reduced or absent in some species, especially ones that live in caves), but ocelli are usually absent (sometimes there are two), represented only by pale areas. Many species have wings; the front ones are narrow and leathery and cover the membranous hindwings when at rest. In some species, males are winged and females are not, and in others, both sexes are wingless. Even winged species usually do not fly; instead they run rapidly on powerful legs. The legs typically have strong ventral spines, the coxae are large, flat and close together; the tarsi have five segments. The tip of the abdomen bears a pair of segmented cerci, and in males there is usually a pair of slender styles on the end of segment 9.

References

Vickery. V.R. and D.K.McE. Kevan. 1985. The Insects and Arachnids of Canada. Part 14. The Grasshoppers, Crickets, and related Insects of Canada and Adjacent Regions. Agriculture Canada Research Branch Publication 1777. Ottawa. 918 pp.