Blattariae - Cockroaches
There are about 3,500 species of cockroaches worldwide, most of them native to the tropics. Cockroaches are flat, fast-running insects with long antennae, long legs and a large pronotum that covers the head almost entirely. They have leathery forewings and thinner hindwings, both held flat on the back when not in use (often shortened (reduced) in females). Like the Orthoptera, cockroaches are hemimetabolic insects, i.e. they do not have a pupal stage. Cockroaches have chewing mouthparts, and most species are omnivorous. Cockroaches often have symbiotic bacteria in special cells called mycetocytes inside their body. The symbionts are passed on to the next generation with the eggs. Cockroaches react very sensitively to sounds and vibrations, which they perceive with long hairs on the cerci. The legs in many species can be autotomised; nymphs can re-grow a lost leg at the next moult. If threatened, several species can produce a foul-smelling secretion from glands in the abdomen.
Reproduction
Females produce a pheromone, which males perceive with their antennae. Males have sac-like glands on their back, which they present to females by raising their wings and “reversing” towards them. Females that want to mate contact these glands with their mouthparts and climb onto the male. Copulation lasts for 1-2 hours with heads in opposite directions. Eggs are laid in a cocoon called an “ootheca” which females hide or carry around attached to the abdomen. The number of instars is variable, for example 9-13 for the Ship Cockroach, Periplaneta americana. The total development time from egg to adult is rather long, more than one year in the case of the Common Cockroach, Blatta orientalis. High densities favour quicker development.
Links
The Blattodea Species File is a taxonomic database of the scientific names of the world's cockroaches (order Blattodea or Blattaria), excluding fossil species and the termites.
The Blattodea Culture Group is a non-profit-making society with worldwide membership with the aim of encouraging the study of cockroaches (order Blattodea).
Mantodea - Mantids
There are about 1,800 species of mantid described to date, mostly from warm regions. Mantids are also hemimetabolous. Mantids have a long “neck”, a very mobile head and strong spiny forelegs that are used to grab prey. They have fully developed wings. Uniquely among animals, mantids have a single hearing organ located centrally on the underside between the hind legs (for detection of ultrasound to evade echolocating bats). Mantids are “ambush hunters”, waiting with raised forelegs (hence the name “praying mantids”) and grabbing passing insect prey rapidly. The Praying Mantid, Mantis religiosa, is the only species occurring in central Europe but has only been recorded in the UK on asingle occasion in 1959.
Reproduction
Female mantids are often larger than males. Males approach females very carefully, freezing if the female moves, and eventually jumping on top of her from behind. During copulation, which lasts about 2 hours, a spermatophore is transferred. Sometimes, though by no means always, the female eats the male during or after mating. Females lay 100-300 eggs in froth that forms a tough cocoon when dry and is usually attached to vegetation. Nymphs go through 5 or more instars before reaching maturity.
Links
The Mantis Study Group site is intended as a resource for anybody working on praying mantids.