Most people would recognise a praying mantis (although they can be hard to spot), but would you be able to identify a mantis egg case?
Common name: Praying Mantis, also known as mantids
Scientific name(s): Any insect in the Order Mantodea, with over 2,400 species in about 460 genera and 33 families. There are approximately 160 species known in Australia.
Description: Praying mantises are well-known enough to need little description, and are named for their upright stance and folded grasping limbs. Their eggs, however, are laid in hard cases attached to any suitable surface, and depending on species may be narrow and under a centimeter long, to large stiff foamy masses several centimeters long.
Geographic distribution: Praying mantises are found in all parts of Australia, including most suburban gardens. Orthodera ministralis, the garden mantis, and Archimantis species, large brown mantises, are common. Miomantis caffra, the Springbok mantis, is a South African species found in Melbourne, at least as early as 2009 and may spread elsewhere in Australia
Habitat: After mating (which can be a fatal experience for the males in some species) the mantis will lay 10 to several hundred eggs in a mass resembling shaving foam; the number, size, shape and colour dependent on the species. The foam soon hardens and darkens, and may become almost woody in texture.
The burying mantis, Sphodropoda tristis, digs a pit in dry sand, lays her eggs, and refills the hole, but most species will attach their eggs to branches, twigs, or any suitable hard surface, which may include fly screens, walls, doors or furniture. Some overseas species will stand guard over the eggs, but Australian species are left alone by the mother.
In colder climates, eggs will be laid in autumn and hatch in spring, but may be laid all year round in tropical climates. Upon hatching and emerging from holes in the mid-line of the egg case, nymphs may hang from the ootheca on chitinous threads until they complete their first moult, and may then try and eat their siblings or scatter in search of other small prey.
Pest status: Praying mantises are important predators of many insect pests, and are disinclined to enter houses. In cooler climates, ootheca brought inside on Christmas trees or pot plants may hatch in mid-winter and the nymphs will likely starve. Egg cases may be attached to wall, doors, or windows, and remain attached for years even after the eggs have hatched, but will not damage the surface underneath.
Treatment: Adult mantis numbers are controlled by competition with other mantises, and predation by birds, lizards, spiders and other predators. Mantis eggs are parasitised by small wasps including Podagrion species, who will hold onto a female mantis’s wings until she starts laying her eggs, but after the wasps emerge the egg case remains intact save for small exit holes.
If laid in an inconvenient place, the ootheca may be carefully removed with a razor or sharp blade, but if possible this should be after the eggs hatch, so the mantises can continue to control pest numbers in the garden.
Daniel Heald, technician and entomologist