Temporal range: 228–0 Ma Late Triassic – Recent
Blattodea is an order of insects that contains the cockroaches and the termites. Formerly, the termites were considered a separate order, Isoptera, but genetic and molecular evidence suggests an intimate relationship with the cockroaches, both cockroaches and termites having evolved from a common ancestor. The Blattodea and the mantises (order Mantodea) are now all considered part of the superorder Dictyoptera. There are approximately 4,400 species of cockroach in almost 500 genera, and about 3,000 species of termite in around 300 genera.
A research study sought to find the phylogenetic relationships between cockroaches and termites. 107 species were sampled including examples of all the termite families and subfamilies, all 6 cockroach families, including 22 of the 29 subfamilies, and 5 of the 15 mantis families (to act as out-groups). Five gene loci were selected for comparison which provided around 4900 aligned base pairs. A maximum parsimony analysis was also undertaken. A Bayesian consensus tree was drawn up and the results showed that the termites are nested within the cockroaches and that Cryptocercus, the only genus in the family Cryptocercidae, is a sister group to the termites. The maximum parsimony analysis provided identical results. The mantids were shown to be the sister group to Blattodea.
Cryptocercus has a number of characteristics in common with termites, such as identical species of gut bacteria, and phylogenetic studies have shown that these cockroaches are more closely related to termites than they are to other cockroaches.
The evolutionary relationships of Blattodea (cockroaches and termites), based on Eggleton, Beccaloni & Inward (2007), are shown in the cladogram: The cockroach families Lamproblattidae and Tryonicidae are not shown but are placed within the superfamily Blattoidea. The cockroach families Corydiidae and Ectobiidae were previously known as the Polyphagidae and Blattellidae.
Arthropods similar to living cockroaches dominated the insect communities of the Carboniferous era. Modern cockroaches radiated from them by the middle of the Mesozoic. The cockroach is flattened dorso-laterally and is roughly oval with a shield-like prothorax that covers the head. The antennae are many-segmented, long and slender, and the mouthparts are adapted for chewing. The fore-wings are normally leathery and the hind wings membranous. The coxae of the legs are flattened to enable the femurs to fit neatly against them when folded. Cockroaches are hemimetabolous; there is no pupal stage and the nymphs resemble the adults apart from their size and the absence of wings.
All species of termite are to some degree eusocial and involve cooperative behaviour among a male and female pair of reproductives, and the workers and soldiers that form the other members of the colony. Some species have small, simple colonies where the workers and soldiers are capable of becoming reproductives themselves. Others have large complex societies where each member has a role that does not change throughout its life. Termites can be considered to be "eusocial, juvenilized cockroaches".
- Integrated Taxonomic Information System entry
- "Order Blattodea: Cockroaches and Termites". BugGuide. Retrieved 2015-08-27.
- Inward, Daegan; Beccaloni, George; Eggleton, Paul (2007). "Death of an order: a comprehensive molecular phylogenetic study confirms that termites are eusocial cockroaches". Biology Letters 3 (3). doi:10.1098/rsbl.2007.0102.
- Djernæs, M. (2012). "Phylogeny of cockroaches (Insecta, Dictyoptera, Blattodea), with placement of aberrant taxa and exploration of out-group sampling". Systematic Entomology 37 (1): 65–83. doi:10.1111/j.1365-3113.2011.00598.x.
- Eggleton, P., Beccaloni, G. & Inward, D. 2007. Invited reply: Response to Lo et al. Biology Letters, 3(5): 564–565 [Published online 14 August 2007. doi: 10.1098/rsbl.2007.0367]
- Beccaloni, G. W. & Eggleton, P. 2011. Order Blattodea Brunner von Wattenwyl, 1882. In: Zhang, Z.-Q. (Ed.). Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness. Zootaxa, 3148: 199–200.
- Bell, William J.; Roth, Louis M.; Nalepa, Christine A. (2007). Cockroaches: Ecology, Behavior, and Natural History. JHU Press. pp. xii, 1. ISBN 978-0-8018-8616-4.
- Choe, Jae C.; Crespi, Bernard J. (1997). The Evolution of Social Behaviour in Insects and Arachnids. Cambridge University Press. p. 52. ISBN 978-0-521-58977-2.