Meadowridge Common

Discovering insect antics! by Susie Brownlie

On Friday 25 September, a small group of the Friends of Meadowridge Common were privileged to host Mike Picker at the Common for an insect walk and talk. Mike is a retired entomologist and Emeritus Professor at the University of Cape Town, and co-author of several books on insects in South and Southern Africa.

Mike started his talk by explaining that Meadowridge Common was originally part of Bergvliet Farm, where the legendary naturalist Dr Frederik Purcell lived in the early 1900s. Dr Purcell was a keen collector and recorder of indigenous plants, spiders and insects in the area. Mike then showed us an exquisite specimen of spoon-winged lacewing (Halterina species). Halterina purcelli had originally been collected by Purcell on Bergvliet Farm and named after him. This species was assumed to be extinct, but recently a Halterina species - possibly the same as that found by Purcell on Bergvliet farm - has been rediscovered at Pella (an intact Sand Plain Fynbos site).

Mike went on to explain that insects could be cosmopolitan (widespread across regions, like the Painted Lady butterfly that can be found on every continent except Antarctica), or be local endemics (like the Cape Stag beetles, Colophon, which have very localised distributions). Local endemic species are typically more specialized, and adapted to specific host plants that only occur in particular habitats (e.g. butterflies restricted to the fynbos biome of the southwestern Cape).

Painted Lady Butterfly and Cape Stag Beetle.

Mike noted the importance of the vegetation type on the Common, namely Cape Flats Sand Fynbos. This vegetation type is Critically Endangered and poorly protected, surviving in remnant patches only. However, much of the Common has been disturbed by human activities and ongoing encroachment by invasive alien grasses, weedy plants, and trees (e.g. pines). For that reason, he did not expect the Common to have a particularly noteworthy or unique insect community. The exclusion of fire in recent years, which is essential for the germination of the seeds of indigenous plants found in this vegetation type, has also reduced the diversity of habitats, plant species, and their insect community.

Mike regaled us with descriptions of the complex, cunning and at times vicious reproductive and survival strategies of insects, including Cockroach wasps, which sting their cockroach prey, paralyzing their nervous system to create ‘zombies’, entirely co-operative in their own demise! Science fiction simply cannot compete with these strategies.

Next, Mike distributed nets, magnifying headgear and trays, and demonstrated how to ‘sweep’ and ‘beat’ to dislodge insects into awaiting trays for inspection. The group took to sweeping grassy areas and beating bushes with enthusiasm, unearthing a variety of beetles, bugs, stick insects, butterflies, wasps, bees, caterpillars and other six-legged beasts. The group’s attention was directed to the wide range of monkey beetles doing headstands inside daisy and other flowers, waving their strong back legs to ward off other males. We then began searching under - and in - rotting logs for earwigs, cockroaches, and other creatures.

The flowers contained a wide range of pollinators (above, clockwise – Common Dotted Fruit Chafer, Scolyiid wasp, Thunberg’s stick insect, and small oval Carpet beetles + Peritrichia monkey beetles).

Although a disturbed habitat, the Common was found to be home to numerous insects! A ‘wake-up call’ for the group, however, was the number of ‘imported’ invertebrates, such as the black millipedes that came from Portugal, ladybeetles and wasps from Europe, and ants from Argentina.

These alien species pose a considerable threat to the survival of our unique native insects, as well as to indigenous trees and plants. Mike emphasized that clearing of invasive alien plants from the Common, restoring degraded areas and re-introducing plants characteristic of Cape Flats Sand Fynbos would help improve its insect diversity. Herbivorous insects have tight-knit associations with certain plants, so increasing plant diversity (using Purcell’s plant list of the area) would be a good way to attract a greater diversity of native insects.

Click here to download a pdf of this article by Susie Brownlie.

Insect Walk with Mike Picker

The Friends of Meadowridge Common were treated to a wonderfully interesting and entertaining insect walk on the Common this morning with Prof. Mike Picker. It started with a look at a most beautiful specimen of Halterina purcelli, a spoon-winged lacewing that was discovered in the Meadowridge Common area by the legendary Frederick Purcell when it was still part of Bergvliet Farm. Although very much degraded and depleted, there are still so many insects to see here including several unusual monkey-beetles and others that we shook out of trees and hunted for under dead tree stumps. Check on iNat for some uploads. See more photos on Instagram.

The delicate spoon-winged lacewing, Halterina purcelli was first discovered on Bergvliet farm by Frederick Purcell.

Meadowridge Common's nocturnal visitors

Cape Porcupines (Hystrix africaeaustralis) are nocturnal rodents, the largest rodents in southern Africa. They are occasional visitors to Meadowridge Common where they forage at night for bulbs, corms and tubers (the nutrient-packed underground storage organs of plants). During the day they shelter in burrows or caves on the slopes of Table Mountain, visiting the suburbs and farmlands at night, often finding their way through stormwater drains and along road culverts. They usually forage alone or in small family groups, communicating with high pitched calls, grunts and quill rattling. On average, they live for about 10 years in the wild, raising one litter of up to three young each year.

Porcupines are covered in coarse, long, black hair interspersed with cylindrical, needle-sharp, black-and-white quills that grow up to 30 cm long on the sides of the porcupine. There is a crest of longer, thinner, more flexible spines that runs from the head down its back. Their quills are modified hairs and will grow back if they fall out. They normally lie flat but can be rapidly erected, making the porcupine appear twice its normal size. If this display doesn’t deter its assailant, the porcupine can charge backwards and sideways and drive home its quills which are easily detachable. They cannot shoot their quills.

You may find evidence of porcupine activity on the Common. Sometimes their footprints can be seen in damp sand, or you will find a discarded black-and-white quill, or a few characteristic lumpy fibrous droppings. They leave distinctive funnel-shaped “foraging pits”, and discarded pieces of the bulbs they dig up. Their enthusiastic digging traps water and organic matter, and facilitates the germination and distribution of seeds and bulbils (small, asexual reproductive structures on many bulbous plants). They are thus important ecosystem engineers in the fynbos.

The bulbs of members of the Iridaceae family such as Watsonia, Babiana, Moraea and Romulea are their staple food source in the fynbos, as are the tubers of the arum (Zantedeschia aethiopica). Porcupines have remarkable defences against the toxins contained in some bulbs, like the Cape Tulip (Moraea collina) which is deadly poisonous to humans and domestic livestock if eaten. The bulbs contain cardiac glycosides that disrupt the cardiovascular, nervous and gastrointestinal systems of most animals. Somehow the digestive systems of the porcupines (and mole-rats too) can neutralize toxins. They can also cope with the microscopic, needle-like calcium oxalate crystals in arums that cause pain, swelling and choking in other animals.

Cape Golden Moles on Meadowridge Common

Meadowridge Common is home to a variety of plants and fungi, mammals, birds, insects and other invertebrates, as well as a whole ecosystem underground that we know very little about. This is why our patch of Cape Flats Sand Fynbos is so important as it conserves a piece of un-transformed fynbos which holds the magic ingredients for being able to withstand a changing climate. Meet some of the creatures that live on the Common.

Cape Golden Moles (Chrysochloris asiatica) are small blind, burrowing, insectivorous mammals, closely related to elephant shrews (or sengis).

They have lots of very small pointy teeth, typical of mammals that eat insects. Despite similarities in looks, they are not related to the moles of Europe and America. Cape Golden Moles occur only in the southwestern and southern Cape, and thrive in the dry sandy soils of the fynbos.

They measure up to 8 cm in body length, with dense, sleek coats that are iridescent in the light. Males and females are the same size. Unlike most mammals, they have a cloaca, a common opening for both reproductive and urinary systems, and therefore have no external copulatory organs.

Cape Golden Moles are infamous among gardeners for their extensive subsurface runs which they excavate with their specialized forelimbs and conical nose shield (rhinarium) in search of earthworms, insects and other soil invertebrates; relying on their acute hearing to locate them. They also dig deeper permanent burrows for sleeping, defecating and breeding. They are solitary, breeding throughout the year, and giving birth to one to three young. Their main predators are owls, cats and dogs.

These moles prey on insects, many of which are harmful to plants and animals. They also enrich and aerate the soil.

Four-striped Fieldmouse on Meadowridge Common

The Four-strped Fieldmouse (Rhabdomys pumilio), or Cape Fieldmouse, is found throughout southern Africa. The four stripes running down its back, and red-brown ears, are its distinctive characteristics. It is active in the day, unlike most mice, and is the mouse you are most likely to see here. It mostly eats seeds and grass and some flowers like vygies and proteas. These fieldmice are important seed dispersers in the fynbos, as they bury more seeds than they can eat. The uneaten seeds are thus stored safely underground, away from fire and other predators, until it is time for them to germinate. This is known as “scatter hoarding”.

Fieldmice and other rodents are also key pollinators of many fynbos plants as they feed on the flowers, and inadvertently carry pollen on their heads, to be rubbed off on other flowers, thereby effecting fertilization.

The fieldmice nest in underground burrows, lined with soft vegetable debris, with entrances at the base of clumps of grass. They also construct round nests above ground, hidden in clumps of grass with a single entrance. In the fynbos, one to three young are born in summer.

They are also prey for key fynbos animals such as diurnal raptors, snakes, mongooses, foxes and caracals.

Cape Mole-rats of Meadowridge Common

Cape Mole-rats (Georychus capensis) are rodents. Look at the shape of the teeth: four huge incisors typical of the rodent family. Like most rodents, they are plant eaters, burrowing through the sand in search of bulbs, corms and tubers. They excavate nesting, food storage and latrine chambers, creating the mounds of sand you can see on the Common. They use their teeth to dig, unlike the golden moles who use their feet. Their lips close sideways behind their incisors to prevent them swallowing sand.

Cape Mole-rats (at 16 cm in body length) are smaller than the Cape Dune Mole-rat (Bathyergus suillus) which can measure up to 35 cm in length and also occurs near the Common. The Cape Mole-rat has characteristic white markings on its head.

Cape Mole-rats are are solitary and territorial. They give birth to three to ten young in spring. They are preyed on by snakes and, if they venture above ground, by owls, herons, dogs and cats. Although their eyesight is poor, they turn on their attackers baring their teeth aggressively.

Their digging activities enrich the soil by adding nitrogen and magnesium, provide refuges for other species, for example to escape fire, and limit surface runoff of water by loosening the soil and increasing drainage and moisture holding capacity.