Though most insect species produce a multitude of eggs, some flies produce live offspring, usually a single young at a time. Many insects mate only once in a lifetime. The cuticle can be modified into a thick, hard armor over some parts of the body or be paper-thin and flexible in other locations, such as the joints of the appendages. The exoskeleton protects the animal and provides points of attachment for the muscles that move the appendages. To grow, an arthropod must occasionally shed its old exoskeleton and secrete a larger one, a process called molting.
Many insects have one or two pairs of wings that attach to the dorsal side of the thorax.
Since the wings are believed to have developed from basal parts of the legs rather than whole appendages, insects are able to fly without sacrificing any walking legs. Insect wings may have first evolved as extensions that helped ventilate the gills or aided in the swimming of aquatic larvae, only later becoming organs for flight. There are many, many different kinds of terrestrial and freshwater invertebrates in British Columbia. Most of these invertebrates are arthropods - insects, spiders, and their relatives. Although many of these are common and widespread, some are confined to the dry grasslands of the southern Interior - and there are literally hundreds that are found nowhere else in the province.