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www.thevillagenews.co.za
13 January 2021
MY ENVIRONMENT
The cockroach hiding in the fynbos By Dr Anina Lee
W
e have all encountered cockroaches of some sort. It's hard to miss them as there are more than 4 500 species of cockroach in the world. Many of them haunt human habitation, where there is plenty of food lying around. Giant roaches crawl out of Cape Town sewers, scuttle across kitchen floors and lurk in cupboards. They will eat anything, so don't stand still for too long. Besides these household pests, which are mainly foreign invaders, there are large numbers of ‘wild’ cockroaches native to South Africa. One of my favourites is the Table Mountain cockroach (Aptera fusca). If you walk anywhere in the fynbos, whether it be in the Fernkloof mountains or on the Cliff Path, they are there unseen, lurking under bark or under stones and other dark, dank places. They come out at night and scavenge on anything dead or rotting. But not always. A female has been spotted on the Cliff Path, feasting on a plant (Blombos) that was very much alive. Being relatively large, (they belong to the family of giant cockroaches) they make quite an impression if spotted during the day. You are most likely to see a female – a large brown insect with bright yellow margins to the segmented body. She is somewhat unusual for a female insect as she has no wings. The males are smaller and have brown wings. They some-
what resemble the ordinary household roach, so you are less likely to notice them.
LEFT & CIRCLE: The female Table Mountain cockroach (Aptera fusca) is somewhat unusual for a female insect as she has no wings. PHOTOS: Pat Miller & Isabelle Betancourt
The mountain cockroach has a very effective way of deterring potential predators. I made the mistake once of interfering with a lovely lady to photograph her better before she scuttled off into the undergrowth. I should not have. She made a loud squeaking noise (by rubbing the roughened edge of one segment of the abdomen against the surface of the next segment) and secreted a brown fluid from her back that stained my hand with indelible brown ‘ink’ that took days to wash off.
BELOW LEFT: The male Table Mountain cockroach is smaller and has brown wings. PHOTO: whatspecies.com
Not only did it leave a stain but also a distinctive ‘cockroach’ odour. The secretion comes from special glands called ‘repugnatorial glands’ – very aptly named. So it's wise to look, but not to touch. Table Mountain cockroaches are unique in that they are social and often hang around with family and friends. It's not unusual to spot a female with a male or two and a whole bunch of nymphs (babies) crowding together in a sheltered spot. As is the case with most animals, cockroach reproduction relies on eggs from a female and sperm from a male. Usually, the female releases pheromones to attract a male. Most roaches are oviparous – their young grow in eggs outside of the mother's body. In oviparous species, the mother roach carries her eggs around in a sac called an ootheca, attached to her abdomen. Many female roaches drop or hide their ootheca shortly before the eggs are ready to hatch. Others continue to carry the hatching eggs and care for their young after they are born. The Table Mountain cockroach (and some other giant cockroaches) differ from ‘domestic’ cockroaches in that they do not lay eggs – they are ovoviviparous. Rather than growing in an ootheca outside of the mother's body, the baby roaches grow inside the mother's body.
The developing roaches feed on their egg yolks, just as they would if the eggs were outside the body. When they are ready, the young are deposited one by one, up to 25 in number. Newly-hatched roaches, known as nymphs, are usually white. Shortly after birth, they turn brown, and their exoskeletons harden. They begin to resemble small, wingless adult roaches. The mother exhibits brooding behaviour, protecting the young with her body for the first few weeks. Nymphs moult several times as they become adults. Between each moult the nymph is known as an 'instar'. Each instar is progressively more like an adult cockroach. The Table Mountain cockroach is not just cuter than your typical household pests, but it also has ecological value in fynbos. It plays a vital role by breaking down plant material to make nutrients available for fynbos growth.
ABOVE: A mountain cockroach seen on the Cliff Path. These insects play a vital role in the ecology of fynbos. PHOTO: Paula Combrink
