Sand Wasp

It’s springtime and the air is full of the sweet scent of flowers and the sound of buzzing insects. Some of the buzzers I’ve spotted recently in my garden are strikingly-colored sand wasps (Bembix sp.).

Sand wasps are solitary hunting wasps that build their nests in the ground. Worldwide, there are over 350 different species in the Bembix genus. They are typically yellow and black and are reported to be particularly diverse in dry habitats. Bedouin in Sinai call all wasps dabra.

Adult sand wasps feed on nectar, but the females are skilled hunters, capturing prey to feed their larvae. The females dig nests in the ground using their mandibles and front legs. The nests are simple burrows with an enlarged chamber at the bottom, the brood cell, which they keep stocked with fresh prey for their developing larvae. It is not uncommon for several females to dig their nests in a common area, but they are not social; they do not cooperate or share the labor.

Flies are the most common type of prey hunted, but sand wasps have also been observed preying on damselflies, grasshoppers, mantids, bugs, antlions, lacewings, butterflies, bees and wasps – but not beetles or spiders. The adult sand wasps catch the prey in mid-air, paralyze them with venom, and then carry them back to the waiting larvae.

After they have had their fill, the larvae spin silk cocoons and enter a prepupal stage. Pupation may not occur until the following spring, and then male wasps will emerge before female ones. Adult sand wasps probably live from several weeks to several months and spend much of their time sleeping. They spend this inactive time within their nests or in temporary sleeping burrows. The adult sand wasps may be prey themselves – to birds, lizards, robber flies, antlions, and velvet ants.

One source I consulted reports that these solitary wasps do not attack and sting humans, but another says they can deliver a painful sting if their nest is disturbed. So, like all stinging insects, it is best just to leave them in peace.

Have you spotted sand wasps on your wadi wanders or in your garden?

Resources:

Evans, H. & O’Neill, K. (2007). The Sand Wasps: Natural History and Behavior. Cambridge: Harvard University Press.

Scarce Marsh Helleborine

If you follow the Wandering through Wadis Facebook page, you might recall the photographs of orchids that I shared a few weeks ago. I had no idea that there were orchids growing in the desert, but after my friend sent me photos of the blooms she had seen, I obviously had no choice but to go see them for myself.

I had identified the orchids in my friend’s photos as Scarce (or Eastern) Marsh Helliborine (Epipactis veratrifolia) but, admittedly, I knew nothing about orchids. So I’ve been reading up on them. And I’ve learned a lot of fascinating things about orchids in general, but also about these rare beauties that are native to Sinai. (They are not found in mainland Egypt.)

Most orchids (more than 99% of all species) are epiphytic and use their roots to attach themselves to and grow on trees. The Scarce Marsh Helleborine, however, is a terrestrial, or ground, orchid and grows its roots firmly in soil.

This helleborine is a perennial herb and grows, from a fleshy rhizome, to be between 25 – 150 cm tall. The leaves are ovate (egg-shaped) and pointed at both ends. They grow along the stem and can be 8 – 25 cm long. The inflorescence, or cluster of flowers, grows atop an erect stem. The flowers are fairly open and are green to yellowish-green in color with purplish or reddish radial stripes. The lip, or bottom middle petal, is tipped in white. The upper part of the stems, bracts, ovaries, and sepals are covered in short, fine hairs. In Dahab, the orchids were found growing among native grasses in a wet area.

Like all orchids, this helleborine is dependent on a mycorrhizal symbiosis, a mutually beneficial relationship between a plant and a fungus, to complete its life cycle. The plant’s fruit capsule is full of microscopic seeds (in some species, over a million), but these seeds all lack endosperm. Endosperm is the tissue usually found inside seeds that provides nutrition to the plant as it sprouts. Because an orchid’s seeds don’t have this inborn nutrition, they rely on fungi to provide them with the nutrients they need to germinate. The chance of germination is so small that only a minute fraction of the released seeds grow into adult plants.

But before a plant can even produce any of these seeds, it must first be pollinated. And to help ensure that, the Scarce Marsh Helleborine employs a trick, a special mimicry, to lure pollinating hoverflies to its flowers. The flowers emit three chemical substances that are usually released as alarm pheromones among aphids. Aphids are the preferred diet of hoverfly larvae. So female hoverflies smell these chemicals, interpret this to mean that aphids are nearby, and proceed to lay their eggs near the source of the scent – the flowers. The hoverflies are rewarded with a small sip of nectar, but their larvae are doomed to starve because, when they hatch, there will be no aphids around to consume. (This is a strange contradiction from an evolutionary perspective because since the larvae die, the number of potential pollinators decreases.) The orchids are mimicking the aphids, taking advantage of the female hoverflies and deceiving them into pollinating the flowers.

As you can see, these rare orchid blooms are not only beautiful but also full of amazing natural wonder!

Resources:

Plants of the World Online (Epipactis veratrifolia)

Orchid tricks hoverflies (Max Planck Society)

The Third Edition is Here!

I’ve had many requests over the last couple of years for print copies of the guidebook. I decided that if I was going to print more, the book should be the best, most up-to-date version possible. So that’s what I’ve been working on, updating the book. It’s been four years since the printing of the second edition, and eight years since the first. I continue to discover and learn about the desert plants and so, to this third edition of the book, I have added 13 new plants (for a total of 155) and 90 new or additional photographs for the plants previously included.

And now I finally have a limited number of print copies available of the third edition of Wandering through Wadis: A nature-lover’s guide to the flora of South Sinai!!

The book is printed on thick quality paper bound with spiral wire 2 cm round. The book is 21 cm x 14.5 cm, about A5 paper size. It weighs 518 grams. Something to consider when deciding if you would want to carry it with you on hikes.
A bonus to reading the eBook version, especially on a tablet, is that you can easily zoom in on the photographs of the plants.

Also, depending on your device, it may weigh less than the print copy. My tablet, in a case, weighs 400 grams (100 less than the print copy).
One useful feature of the PDF version, especially when read on a laptop or PC, are the bookmarks that help you easily navigate through the book.

You can download a sample of the book as a PDF file for free here . This requires an email address. If you’d rather not enter an address, click the ‘Preview’ button on the top of this page to view the file online.

Print copies cost LE 400, including free delivery in Dahab. Shipping is possible within Egypt. Send me a message to arrange purchase and delivery of your copy.

The eBook version has also been updated and can be purchased online for $8 here. Contact me if you would like to arrange alternative payment and delivery options. Enter code WADIBLOG for a 10% discount.

Happy Wandering!

~Bernadette

Desert Plant Adaptations (IV) ~ Leaf Adaptations

Getting back to my series on desert plant adaptations, let’s discuss some of the ways that leaves have adapted to help plants survive the hot and dry conditions of the desert wadis.

Besides dropping all of their leaves like drought-deciduous plants, some plants simply have smaller or fewer leaves. Smaller leaves means there is less surface area open to the wind and sun, and so less water is lost through transpiration. Semi-shrubs and shrubs may have large leaves in the winter that are shed during the dry season and are replaced with smaller leaves in the summer. Artemisia herba-alba and Phlomis aurea both have smaller summer leaves.

Another strategy that helps conserve water is folding or rolling up the leaves so that the stomata are facing inwards, reducing the surface area subject to transpiration. This adaptation is employed by Helianthemum species, Fumana thymifolia, and many perennial grasses.

But it’s not just transpiration that leads to water loss. Leaves also lose water through their cell walls. To combat this, the leaves of some desert plants have a waxy coating or a thick cuticle, the film covering the surface, which helps seal in and protect moisture already in the leaves. Most xerophytes have a thick cuticle.

Hair on the leaves and stems also helps reduce water loss by providing shade and trapping water vapor near the plant’s surface. Artemisia herba-alba, Phlomis spp., Majorana syriaca, and other plants utilize this adaptation.

Plants needs energy from the sun to photosynthesize. What energy they don’t use to make food is used to heat the leaf up. That is very useful for plants growing in cold climates whose leaves need to be a bit warmer to photosynthesize but not so necessary for desert plants, which must reflect some of this solar radiation or risk over-heating. How do they do this? Some plants, like Capparis sinaica, have a waxy coating on their summer leaves which gives them a lighter – and more reflective – color than their winter leaves.

Leaves of Atriplex species also have a different color depending on the season, but they don’t use a waxy coat. Instead, the leaves are covered in vesicular hairs that contain a salty solution. In the winter, the hairs are full and transparent, allowing more absorption of the sun’s energy. In the summer, the water evaporates and the hairs dry out causing the leaves to be a lighter color that reflects the sun’s rays.

You can read more about each of the species photographed above in my book. In the next post in this series, we’ll learn about stem adaptations. Stay tuned!

Pantropical Jumping Spider

Over the past several years, I have really come to enjoy watching the jumping spiders in my garden and, of course, while wandering through wadis. The Pantropical Jumping Spider (Plexippus paykulli) is one of the more common – and dramatically-colored – ones that I can see close to home.

I was not surprised, then, to learn that this species is often associated with buildings and man-made structures and may be found near light sources.

Both sexes of this species have a high carapace (upper section of the cephalothorax, the front part of the body where the legs are attached) and are covered in short grayish hairs.

Males, pictured above, have a black carapace and abdomen with a broad white stripe running through the center. There are also broad white stripes along the sides and a pair of white spots towards the rear end of the abdomen. The face appears to have three white stripes, which you can see clearly in the close-up photo below.

Immature spiders, as well as females like the one pictured below, are brownish-gray in color with a broad tan stripe through the center of the carapace and abdomen. Towards the end of the abdomen, the stripe breaks into chevrons, v-shaped marks.

Like all jumping spiders in the family Salticidae, Pantropical Jumping Spiders have incredibly acute eyesight. They have four pairs of eyes, with the middle pair in the front quite a bit larger than the others.

“Hoppeedderkopp” by hornet81 is licensed under CC BY-ND 2.0

These jumping spiders do not spin webs. Instead they use their silk to build ‘retreats’ in high-up places where they can rest safely when not hunting. Once they have spotted potential prey with those amazing eyes of theirs, the spiders go into stealth mode and approach, leaping only when they are close enough, but not before attaching a dragline. And these spiders can jump! They can cover many times their body length in a single leap.

These aptly-named spiders will pounce on and eat flies, bugs, bees and wasps, butterflies, dragonflies, grasshoppers and other spiders. They can reportedly kill prey that is twice their size. They do this by first injecting the prey with venom and then overpowering them by brute force while the prey is still mobile.

Desert Mantis

Camouflaged against the stones and gravel, desert mantises (Eremiaphila spp.) are so cryptic that they are difficult to spot unless they are moving.

They are well-adapted to arid habitats, and there are 31 different Eremiaphila species recorded in Egypt.

Desert mantises are voracious ambush predators, waiting patiently until their prey is spotted and then pursuing their victims quickly and grasping them with their spiked forelegs. Because their hunting relies heavily on vision, desert mantises are diurnal, or active during the day. They are very flexible, able to move their heads without moving their whole bodies, allowing a large field of vision.

Although flightless, adult desert mantises have small wings, as seen in the magnified inset below.

Have you spotted desert mantises on your wadi wanderings?

Huntsman Spider

I have not been able to photograph a huntsman spider yet, but a friend in St. Katherine has and generously shared her pictures so I could write a post about this beauty!

This is a spider in the huntsman family of spiders (Sparassidae), specifically Eusparassus walckenaeri. There are 33 spiders in the Eusparassus genus, and they can be found in Africa, Asia, Europe, and Peru. Huntsman spiders are known for their incredible speed. In fact, it’s because of their lightning speed that the Jebeleya Bedouin call them beraira.

These huntsman spiders are large with flat bodies that are dark brown to orange-brown in color, with a pattern of spots and chevrons. The bodies can be from 1 to 2.5 cm in length, with the females being larger. The legs have dark bands of color and, although the legs of most spiders are perpendicular to their bodies, the legs of huntsman spiders are not. Their legs are angled and twisted in such a way that they move with a sideways crab-like motion. (Huntsman spiders are sometimes called giant crab spiders.)

Huntsman spiders are nocturnal hunters and feed on small and large insects, especially cockroaches, so a spider would be a welcome find in your home! And there’s no reason to be afraid of them; their venom won’t hurt you.

While these spiders may be imposing hunters, they are, of course, prey to other animals, especially to a family of wasps known as “spider wasps” (Pompilidae). A female spider wasp uses its venomous sting to paralyze a spider and then drags the spider to her nest or burrow. There, she lays an egg on the spider, which is anesthetized but alive. The wasp larva hatches and proceeds to feed on the spider, saving the vital organs for last, until it finally spins a cocoon and eventually emerges as an adult wasp.

These huntsman spiders can be found in open ground, but I have never spotted one in the wadis. They can also be found indoors and I’m pretty sure I have seen (some species of) huntsman spiders scuttle through the communal seating area of a camp in Ras Sidr. Have you spotted these huntsman spiders in South Sinai?

Resources:
Aly, D. & Khalil, R. (2011). Wildlife in South Sinai. Cairo. Funded by the E.U. in cooperation with G.O.S.S.

Desert Plant Adaptations (III) ~ Drought-escaping Plants

I’ve written about two general strategies that plants employ to survive in desert habitats – succulence and drought-deciduousness. Today I’ll introduce the most successful adapters to life in the desert – drought-escaping plants. Plants escape drought in one of two ways. They either survive only as seeds or they use taproots.

Annuals are plants that wither and die during the dry seasons but not before completing their life cycle, sometimes in just a few weeks. Their seeds are covered by a thick protective coat and are dispersed, only to wait underground as part of the desert’s “seed bank”. Contained within their seed coats are certain chemicals that prohibit germination. The seeds must wait for rain to wash these chemicals away before they can sprout. These are the plants that amaze us here in Sinai when our desert sands are suddenly covered in green after a spring rainstorm. These are also the plants that are so important to the Bedouins’ herds of goats and sheep. Some of these annuals that survive dry seasons as seeds include Astragalus spp., Artemisia spp., Diplotaxis spp., and Tribulus spp. and are pictured below.

Using taproots is also a successful strategy to avoid the problems associated with drought. A taproot is a very thick and long root that grows directly downward. Think of a carrot. The taproot is the main central root which other smaller roots grow off of. The long taproot allows the plant to reach water stored deep underground, providing an almost constant source of water. The taproots of Convolvulus lanatus, pictured below, and Artemisia monosperma are also covered with a thick bark that helps the roots to withstand the withering caused by wind.

You can learn more about these desert plants in my book, Wandering through Wadis: A nature-lover’s guide to the flora of South Sinai.

Desert Plant Adaptations (II) ~ Drought-deciduous Plants

It’s been longer than I had planned, and I’m not sure where the time went (well, a lot of it went to waiting for a new computer when my old one bit the dust), but I’m finally back with more information about how the plants in South Sinai have adapted to survive the harsh desert conditions! In the first installment of this series, I talked about succulence, the ability of plants to store water in their leaves, stems, and/or roots.

Lycium shawii, Desert Thorn

Today, I’ll discuss drought-deciduous plants. Instead of storing water like succulents, these plants use a different method to deal with drought conditions. During the dry seasons, they drop their leaves, allowing them to save water that would otherwise be lost during transpiration (similar to sweating in humans).

Because these plants don’t have their leaves to make food in the summer, their stems take over the photosynthesis process. (More on this in a future post.) Drought-deciduous plants also slow down their metabolism, making only enough energy to keep the plant alive. This means when conditions for growth are favorable again, the plants don’t have to start from zero. They’re already idling and ready to go, if we think in car terms; they don’t have to turn the ignition on first.

Lycium shawii, or Desert Thorn, is one example of a plant that is completely leafless in the summer. (It also has succulent leaves, so more than one adaptation to help it survive.) And because I don’t hike in the summertime, I don’t have photographs of this plant without leaves. But here’s a pic of their beautiful lush leaves:

In my next post, I’ll discuss the most successful adapters to life in the desert – the drought-escaping plants – so be sure to follow the blog or the Facebook page so you don’t miss out!

Desert Plant Adaptations (I) ~ Succulence

Plants that have adapted to living in dry habitats are called xerophytes, and they are the characteristic plants of deserts and semi-deserts. Over the next few weeks, I’ll be explaining some of the adaptations that allow them to survive in such a harsh desert environment. And it is harsh! Besides the limited supply of water, these plants must also survive high daytime temperatures, high levels of solar radiation, high levels of salinity, and strong winds. Water, however, is the most important ingredient in their lives and they must prevent water loss and overheating to survive. In general, to overcome these obstacles, desert plants can be classified into three main groups according to how they deal with the drought conditions – succulence, drought-deciduous, and drought-escaping. Today, I’ll talk about succulence.

Succulence is the ability of plants to store water in their leaves, stems, and/or roots. Cacti are a classic example. Succulent plants have shallow roots, allowing them to quickly absorb any available moisture, including dew. These plants can begin to grow 24 – 48 hours after rain. You may have noticed that there aren’t many cacti growing in the wadis of South Sinai, but there several species of succulents.

Species with Succulent Leaves

If you think back to your high school biology class, you’ll recall that photosynthesis is the process that allows plants to use the sun’s energy to convert carbon dioxide (CO2) and water into sugar. Basically, it’s how plants make their food. There are pores, called stomata, on the leaves that open and close to absorb carbon dioxide from the air and release oxygen. When these stomata open and close, water vapor is also released and evaporated. This release of water is called transpiration. It’s similar to sweating in humans and can help cool the plant. And we know that if we sweat a lot, we should drink more water to stay hydrated. However, desert plants do not receive a lot of rain to replace this lost water. So they have adapted to conserve as much water as possible.

Species with Succulent Stems

One way succulents do this is to use a different type of photosynthesis, one that allows the plants to make food without losing a lot of water to transpiration. It’s called crassulacean acid metabolism, or CAM photosynthesis. Plants that use CAM open their stomata at night when temperatures are cooler and keep them closed during the day. Instead of using sunlight to convert the CO2 to food right away, plants store the CO2 they absorbed at night as crassulacean acid. As the day begins and the temperature starts to rise, the acid is changed back into carbon dioxide and then used in photosynthesis. This allows the plants to conserve water and use it to make food instead of losing it to evaporation.

Species with Succulent Stems and Leaves

That’s a pretty fascinating adaptation, isn’t it? But it’s only the start! Stay tuned for my next post where I’ll discuss drought-deciduous and drought-escaping plants.