Blattodea

Lore & Background

Termites are pale-coloured, soft-bodied eusocial insects that live in colonies with a biological caste system. A pair of sexually mature reproductives, the king and the queen, breed to produce all other individuals within the colony, consisting of numerous sterile workers and soldiers. In contrast, cockroaches are pigmented (often brown) and possess sclerotised body parts hardened with sclerotin. Cockroaches are not colonial but have a tendency to aggregate, with some species considered pre-social as all adults within a social group are capable of breeding. Termites and cockroaches share several similarities, including various social behaviours, trail following, kin recognition, and methods of communication.

Cladistic analysis of five DNA sequences in 107 species representing all termite subfamilies, all six cockroach families, and five of the 15 mantis families showed that termites are nested within cockroaches, and that the monotypic Cryptocercidae is a sister group to the termites. This is reinforced by Cryptocercus sharing characteristics such as particular gut bacteria species with termites. The mantids were shown to be the sister group to Blattodea. The evolutionary relationships of the Blattodea, based on Eggleton, Beccaloni & Inward (2007) and modified by Evangelista et al. 2019, depict the family Alienopteridae as sister to Mantodea; while it was reassigned to the extinct Blattodea superfamily Umenocoleoidea by Vršanský et al., a more recent analysis places Alienopteridae and Umenocoleidae as sister taxa within Dictyoptera, and not within Blattodea.

Over 4,000 species of cockroaches are found on every continent, each with its own indigenous species. Most are omnivores or detritivores and live in habitats such as leaf litter, rotting wood, thick vegetation, crevices, beneath bark, under logs, and among debris. Some are arboreal, some live in caves, and some are aquatic. A small number of species have taken to living in close proximity to humans in buildings and are regarded as pests. Over 3,000 species of termite are found on all continents except Antarctica, with the greatest diversity in Africa. They are also detritivores, and many species eat wood, having specialised guts with symbiotic protozoa to digest cellulose. Termites have soft bodies and keep out of sight as far as possible; they can be loosely subdivided into dampwood, drywood, and subterranean types.

Reader's Guide

The significance of Blattodea lies in its demonstration of how eusociality evolved within a lineage of otherwise non-colonial insects. The placement of termites within the cockroach order, supported by genetic and molecular evidence, fundamentally changed the understanding of insect phylogeny and social evolution. The shared behaviours between cockroaches and termites—such as trail following, kin recognition, coprophagy, and attraction to warm, humid places—suggest these traits were inherited from a common ancestor. The cockroach family Cryptocercidae is particularly important as a sister group to termites, sharing gut bacteria and egg-laying in oothecae, providing a window into the transition from pre-social to eusocial organisation. Blattodea also includes species of major economic and health importance as pests in human dwellings, while termites play critical ecological roles as decomposers of wood and plant material. The order's diversity—over 7,000 species across cockroaches and termites—and its global distribution underscore its ecological and evolutionary importance. The ongoing debate over the placement of fossil groups like Alienopteridae highlights that the phylogeny of Dictyoptera remains an active area of research.

Did You Know?

• Termites were formerly classified as the separate order Isoptera but are now considered a divergent group of cockroaches within Blattodea.
• The cockroach family Cryptocercidae is a sister group to termites and shares characteristics such as particular gut bacteria species with them.
• A single termite kept alone has a significantly decreased level of vigour and a shorter lifespan than when two are kept together.
• Young cockroaches obtain much of their nourishment from eating the fecal pellets of larger individuals, acquiring microbial flora that helps digestion.