APRIL 2021

APRIL 2021

 

With a mere average of 6,5mm rainfall this month, the rainy season has come to an end and so another cycle is past. It is also the end of the burning season and the above photo shows a successful patch mosaic burn (see blogs of: November 2017 "A successful Burn"; August 2018; February 2020; October 2020; and April 2019 for info on patch burns) on the boundary between us and Emoyeni, on the lower south western slopes of Mount Anderson, instead of a fire break there this season. And although the new season is cold and dry and there is less wildlife to see, I still got to see so many interesting things out there this month. Below is a gallery of some of those things:

My goodness! What an odd-looking fly. The head looks as if it has been molded from plastic. It is a Spring Bee-grabber, a type of Thick-headed Fly from the Myopa genus in the Conopidae family. Members of this family grab a Honey Bee or even a Bumblebee overseas, in flight, with those powerful legs and then, with the aid of a modified ovipositor that acts as a crow-bar, forces the bee's abdominal segments apart and deposits an egg within. Then they let the bee go again and it flies off and continues on its way. The egg hatches and the fly larva begins devouring the host bee from the inside. The fly is a Protelean parasitoid, just like the Ichneumonid wasps mentioned in last months blog, and a few others in previous blogs. Protelean parasitoids are organisms that are parasitic in their larval stage and kill off the host that they parasitised. They then emerge from the dead host and lead non-parasitic adult lives. A slight difference between these flies and the ones I've mentioned before is that the host bees behaviour becomes erratic when parasitised by the fly maggot and there have been observations overseas where Bumblebee victims seem to forget to return to their nests and are found thawing out, in the open, the following morning.

There always seems to be more ticks, especially Pepper Ticks, which are six-legged tick larvae (as opposed to eight-legged nymphs and adults) in our grasslands during winter. That's because sightings of female Leather ticks like this, from the Rhipicephalus genus, that are full of developed eggs are a common site during the autumn months when they each lay thousands of eggs. The eggs hatch at the beginning of winter and after finding a host and enjoying their very first blood meal, the tick larva, or Pepper tick, drops off their host animal and enters their nymphal stage and after moulting, the nymph acquires it's other pair of legs. Ticks belong to the Arachnida class of arthropods together with spiders, scorpions, mites, solifuges, whip scorpions, pseudo scorpions and harvestmen who have all featured at some time or another on this site. They have the eight legs, chelicerata and pedipalps of all of the above but, together with mites, their body segments have fused together to form a single blob of a body. One thing unique to ticks is the presence of sensory organs, called Haller's organs, on the last segment of each front leg. These pit organs full of bristles analyse the carbon dioxide content in the air, the humidity, temperature and can even receive infrared signals, all to aid the tick in finding a host animal for its blood meal. Ticks have a few other remarkable adaptions to allow them to survive the uncertain availability of the three animal hosts they require to complete their life cycles. Like the ability to slow their metabolism right down to allow them to go without food for almost a year. During these tough times they have the ability to gather water from the air through hygroscopy, the adhesion of water molecules to their external mouthparts. When requiring a host, the tick partakes in a behavioral phenomenon called "Questing" where it clings to a piece of vegetation, like a grass stalk or a leaf, with its back two pairs of legs and stretches out its front two pairs of legs, ready to grab hold of a passing animal host, something that is quite commonly observed during our hikes through the grasslands here at Finsbury. The tick gorges itself on the blood from the host until it is ready to moult when it will drop off the host onto the ground (before or after the moult) and, now in its next life phase, will begin the task of seeking it's next host. Males will find females during their final blood meal and mate with them on their host. After about three years of life, the female's eggs develop inside her and she grows many hundreds of times larger to look like the one in the photo. Then she drops off her host one last time and lays thousands of eggs and the whole cycle starts again.  

This is what remains of a massive, majestic African Almond tree, Prunus africanus, that was felled by Eloise recently. It lies across the river from the path to the Steenkamps waterfalls as it meanders through the evergreen forest. The Prunus genus from the rose family contains many familiar trees like peach, apricot, plum, cherries and almond. This, one of the only species in Africa, is the largest, though, reaching heights of forty meters. It is a beautiful tree, with glossy green leaves that smell of almonds when crushed and very dark, roughly fissured bark. The leaves have nectary glands along their margins, a clever defensive strategy. Nectaries are usually found in flowers and produce the sweet nectar that attracts pollinators so that they will transport the pollen from one flower to the other. The nectaries on the leaves are also attractive to insects, but not pollinators but bodyguards instead. In my blog of January 2020, I featured a little blurb about the relationship between aphids, the sap-sucking insects, and their protectors, Long-legged Sugar ants that lap up the sweet honeydew that the aphids produce as a reward for the protection the ants provide. Well, the nectaries on the leaf margins achieve the same sort of protection from the ants. But this time from caterpillars, sap-suckers and even large herbivores that don't want to get a mouthful of stinky ants when browsing the leaves. Unfortunately for this magnificent tree, the bark is in great demand by traditional healers because extracts from it supposedly cure a long list of ailments and so the tree is listed as vulnerable with a decreasing population. In fact, it has become locally extinct in half the forests of KwaZulu Natal and it is rare in the others. Because of this, and the fact that they only occur in evergreen forests, which is the smallest biome in South Africa, it is estimated that there are less than ten thousand adult individuals left in South Africa and in Mauritius and the rest of Africa, they are in even more trouble. It is, then, quite sad to see such a magnificent specimen downed. Even if it was by natural causes. 

I found this pair of Mole snakes, Pseudaspis cana, intertwined on the road just where "The Croft's" driveway joins the entrance road. I first thought it was a mating pair but when I look at the literature, it says that they have a mating season and it is in the late spring time. This is the time that they give birth so my sighting could only have been two males having a scuffle. Also odd, though, because although Mole snakes are not venomous, they have broad, strong and very sharp fangs that cause deep wounds on foolish people who try to handle them and other male snakes when they fight. I did not notice any bloody wounds on these individuals and the mess of tracks on the road suggests they were at it for a while. Anyway, they are viviparous which means they give birth to live young and this they should be doing about now. Normally about fifty young are born but the record by a female in an institution in London was 96 babies, each about twenty centimeters long at birth (that female was almost two meters in length). One tends to find small, young Mole snakes in rocky areas and larger adults in more sandy areas because they feed mainly on lizards and skinks when they are young but change to a diet of mostly moles and mole-rats as adults. They will push themselves through a freshly produced mole hill and wait in the runway for the unsuspecting mole or mole-rat to return. Although they are common large snakes, I have not seen one longer than seventy centimeters on the estate.   

During autumn time the grasslands on the estate are lit up by fields of yellow flowers and many people ask me what they are. I cannot find an English name but the Afrikaans name is Geel Blombos, translated to Yellow Flowerbush in English (see blog of May last year). The proper name, Phymaspermum acerosum, is also quite descriptive (if you know what the seed looks like) because it means "swelling seed with needle-like leaves". This is a picture of the very poisonous Stinkweed Locust (see blog of November and December 2020) perched atop the bright yellow inflorescence of a Geel Blombos alongside Kingfisher Lodge (Unit 6)

This beautiful little butterfly with a three centimeter wingspan is common throughout the year here on the estate. It is called a Dancing Acraea and it is one of those really difficult species to group because it has been changed taxonomically twenty five times since it was first described in 1780! Now it is either Hyalites eponina or Acraea eponina. It is found throughout Africa and in Arabia and in all of that range it only eats from plants in the Mallow family as a caterpillar and here it almost exclusively feeds on the leaves of a small, non-descript little bush in the open grasslands with pretty yellow, bell-shaped flowers that hang down called a Hermannia montana. The common name reflects its habit of dancing back and forth just above ground level as it moves over the grasslands.

One of the nicest things about this time of the year is the fact that the African Blueberry bush, Vaccinium exul, is fruiting. The genus is home to the cultivated blueberry, the cranberry, the bilberry and the huckleberry. And yes, the fruit does not just resemble the cultivated blueberry but is just as tasty. The Heath family, Ericaceae, is only represented by two genera in South Africa: the Erica genus with about seven hundred species, mostly in the Cape Floral Kingdom, and the Vaccinium genus with only one representative, this chap, and that is where the specific name of exul (meaning exile) comes from. Although they grow into medium sized trees of up to seven meters high in Malawi, here they grow as bushy shrubs only at high altitudes in our escarpment grasslands. The fruit is not only very tasty but also contains many potential benefits: It is high in vitamin C and contains high levels of antioxidants; it reduces the build-up of low-density lipoprotein cholesterol in mice; also in mice it is responsible of the reversal of some aging effects like loss of coordination and balance and short-term memory loss.

This is a photograph of a distant but very noticeable Ground Woodpecker, Geocolaptes olivaceus, sitting flat on a rock with its tummy on the floor which is characteristic of the species. A typical scene where the sentinel screeches his / her alarm call, alerting the others in the group that you are nearby before you have had a chance to see them. These birds are endemic to the eastern escarpment in South Africa, Swaziland and Lesotho and the Cape fynbos mountains and, although locally common, are always a special species to see and a lifer to many. Breeding pairs are territorial and sedentary, which means they are monogamous and remain in the same area year in and year out, and once they have successfully fledged their offspring, the offspring remain with their parents, in a family group, until the following breeding season when they disperse to find their own mates. Together, both sexes excavate a meter long tunnel eight centimeters in diameter with a chamber at the end into a hard, vertical earthen bank which is used for nesting and, unlike most birds, for overnight roosting as well during the rest of the year. Makes sense since there are very few big tree to safely roost in in their preferred habitat. The pair or family group exit the hole at sunrise and sun themselves on a rock before they move off to forage for ants which are almost exclusively their food. They leave a sentry on guard while the others probe the ground for the passages of an ant nest, into which they insert their long, sticky, spaghetti-like tongues and extract ant larvae, pupae and adults. 

This ugly critter is a Tachinid fly and the adult feeds on nectar from flowers and honeydew from aphids and others. This makes them quite important pollinators on the escarpment because bees are concentrated on the lower altitudes which leaves the higher altitudes to these and oil beetles and the like. They are also protelean parasitoids (see the Beegrabber above) but these flies have a long, coiled uterus so that the egg, when it is laid on the body of the host, is already well developed so that it hatches very soon after laying and the larva then has to burrow itself into its host. So if you see a beetle, or almost any other insect with a snow white egg stuck to its body, you will know who that egg came from.

This is a twelve millimeter long Harvester ant, Messor capensis, with seed which it is carrying back to its nest. The name "messor" is the name given by the romans to their god of crops and harvest. The colonies of these ants are large and founded by a single queen ant and they live in a huge, complex nest with many passages and chambers. Some of these chambers have been especially constructed to stay as dry as possible, as granaries, to ensure the seeds stored there don't germinate. The worker ants, who range in size from small to big, wear well worn paths to their harvesting grounds and use them until they exhaust the seed supply in that area. The biggest workers, the Nutcrackers, have huge, rounded heads with blunt jaws and are used exclusively to crack the shells of the largest seeds. When the workers return to the nest, laden with seeds, they remove the seeds from the husks and leave the husks around the entrance to their nest while taking the seeds to the granary. Strangely, if one opens the nest up in the winter time, one will find some of these chambers filled with the heads of the large workers. It is believed that the colony feeds on these workers when food is at its scarcest. In the Cederburg in the Western Cape, some farmers still use these ants to gather Rooibos, Aspalathus linearis, seeds from the floor of their fields. You see, Rooibos have minute seeds that develop inside pods and when ripe, the pods burst open, spreading the seeds over quite a distance. This together with their size, makes it almost impossible for the farmers to collect the seeds so they raid the granaries of the harvester ants for the seeds the ants have collected. Very clever! 

I had to include this fly just for the bizarrely patterned eyes! It is a Bar-eyed Hoverfly, Eristalinus taeniops, and if you could see the rest of its body you would see a similarity to a honey bee. This provides them with a certain amount of protection from some enemies who are afraid of the bee's sting (which the fly doesn't have!). This mimicry, when a harmless insect mimics a harmful insect, or a tasty insect mimics a poisonous insect, is called Batesian mimicry as opposed to, let's say, Mullerian mimicry, where a poisonous insect mimics another poisonous insect. or a harmful insect mimics another harmful insect. The problem with Batesian mimicry is that predators often have to learn which colours mean danger on its prey animals by eating one and getting sick because it was poisonous or getting hurt because it was harmful, only to learn that in the future it will not go near an insect that looks like that again. So Batesian mimicry only works when the population of the mimic does not exceed twenty five percent of the population of the model because, if that happens then the predators will probably eat the harmless ones as well and decide that not all prey items that look like that are harmful and this will negate the effect of the aposematic colouration (warning colours). A good example illustrating this fact is a species of butterfly, a Common Diadem, where the female mimics an African Monarch butterfly which is very poisonous. The Common Diadem keeps the mimicry low by only allowing the females of the species to mimic the Monarch while the less important male Diadem looks like a completely different species of butterfly. Even more clever!

Another month has passed and, as we go into winter, I see that the third wave of the Coronavirus is on the horizon. Stay aware of this virus and practice care so as not to be one of those that help spread it. The vaccines should be available in the near future so let's hope that this thing will be over soon. Recently, I inserted an activities section into the back of your house files. If you would like me to guide you and your friends on any one of those activities, or any others, radio me when you get here or, even better, send me an email requesting a guided hike a week or two before you get here at jimmy@finsbury.co.za. Dress warm!