The Phasmatodea are large to very large terrestrial insects, inhabiting chiefly the warmer parts of the world, especially the tropics. They have attracted wide attention because of their size
a few species exceeding 30 cm in length
and the remarkable resemblance of most of them to sticks or leaves.
The wingless, parthenogenetic
is a widely studied laboratory animal.
The stick-insects were long treated as a family within the Orthoptera. They are now given ordinal rank, but under a variety of names: Cheleutoptera, Phasmida, Phasmodea, Phasmatodea, Phasmoptera, Phasmatoptera.
The works of Beier (1957, 1968), although in some respects outdated, remain the most comprehensive accounts of the order. The book,
Stick Insects: Phylogeny and Reproduction
(Eds Mazzini and Scali 1987) contains a number of important papers on subjects covered by the title and some others. Basic structure and habits are rather uniform. More than 2500 species are known.
Brock and Hasenpusch noted in their book (2009) that the Order now consisted of three families, the Phasmatidae, Phylliidae and the Diapheromeridae.
Mandibulate, phytophagous, exopterygote Neoptera, having all legs gressorial, with small, well separated coxae; pronotum without large descending lateral lobes; wing rudiments of nymph not reversing their orientation in the later instars; specialised auditory organs lacking; eggs free, thick-shelled, provided with a conspicuous operculum.