Archives

Mozambique Diary: Sibylla

A portrait of the Precious Sibyl mantis (Sibylla pretiosa) – it is easy to get the impression that this insect really thinks.

A portrait of the Precious Sibyl mantis (Sibylla pretiosa) – it is easy to get the impression that this insect really thinks.

These days, if God speaks directly to you, be it about the precise date for the end of the world or his opinion about somebody else’s sexual preferences, you are either a crazy nut or a Westboro Baptist crazier nut. Ancient Greeks, clearly more open minded about such things, referred to a woman with powers to prophesy God’s actions with a much nicer-sounding honorific – Sibyl. Perhaps the 19th century Swedish entomologist C. Stål saw some of that craziness in the facial features of a gracile praying mantis from southern Africa, and christened it Sibylla pretiosa – the Precious Sibyl. Looking at this remarkably anthropomorphic insect it is indeed easy to get the impression that some strange thoughts are percolating in its brain.

The Precious Sibyl mantids (Sibylla pretiosa) are usually found high on the branches of savanna trees.

The Precious Sibyl mantids (Sibylla pretiosa) are usually found high on the branches of savanna trees.

I first encountered Sibylla many years ago in Zimbabwe, amazed at the sight of large mantids, nearly ghost-like in their slender built and pale coloration, that were zipping up and down smooth tree trunks. Last year I once again found Sibylla while collecting insects high in the canopy of a large Combretum tree in Gorongosa National Park. Alas, it was a tiny nymph. This month, however, while in Gorongosa during the peak of the rainy season, Sibyllas were plentiful on tree trunks and at the lights of the Chitengo Camp.

A male Sibylla cleaning his antennae.

A male Sibylla cleaning his antennae.

Despite their fragile appearance, these insects are skilled hunters, capable of catching and devouring prey at least half as long and nearly as heavy as themselves. They slowly stalk crickets and moths found on the bark, constantly vibrating their antennae in a fashion similar to that in many parasitoid wasps, which may indicate the use of chemical signals in detection of their prey. I have also seen these mantids feeding at night, which further supports the possibility of using non-visual cues while hunting.

Young Sibylla are very spindly looking and are found usually on leaves and tips of thin branches.

Young Sibylla are very spindly looking and are found usually on leaves and tips of thin branches.

Although superficially similar to empusid mantids, Sibylla is more closely related to another amazing dead leaf mimic, the Ghost mantis (Phyllocrania paradoxa), which I yet need to find in Gorongosa (but I was told by a resident that he had seen one). Most of the 14 known species of the genus Sibylla are found in West and Central Africa, and the individuals from Gorongosa are the first records of this genus of insects in Mozambique.

Sibylla mantids are closely related to the otherworldly Ghost mantids (Phyllocrania paradoxa). I have not yet found one in Gorongosa, but I am pretty sure that we have them there.

Sibylla mantids are closely related to the otherworldly Ghost mantids (Phyllocrania paradoxa). I have not yet found one in Gorongosa, but I am pretty sure that we have them there.

Alas, having caught quite a few individuals of Sibylla attracted to my mercury vapor lamp in Gorongosa, I am now convinced that this pretty insect does not have the powers to foretell the future. Otherwise they would have known that if you come to my light, you never leave.

Sibylla are voracious predators of insects found on tree bark and branches.

Sibylla mantids are voracious predators of insects found on tree bark and branches.

Mozambique Diary: The Cat mantis

I decided to christen this impressive praying mantis (Heterochaeta orientalis) the Cat mantis, on the account of its head morphology, but even its defensive behavior reminds me of a cranky cat (is there any other kind?).

I decided to christen this impressive praying mantis (Heterochaeta orientalis) the Cat mantis, on the account of its head morphology, but even its defensive behavior reminds me of a cranky cat. (Is there any other kind?)

Arriving in Gorongosa National Park in Mozambique at this time of the year, when the grasslands are bone dry and green has all but disappeared from the color palette of this immense ecosystem, I did not expect to see too many insects. Sure, there will always be ants and a bunch of grasshoppers, but the bulk of the insect fauna pretty much disappears until the onset of rains in November. The nights are quite cold when the atmosphere is devoid of the buffering layer of humidity and consequently few insects are active around the lights of the camp. But those that do come are often stunning. Some of the first animals that I spotted when I resumed my nightly patrols around the lights of the Chitengo camp were huge praying mantids Heterochaeta orientalis, whose head morphology immediately brought to my mind a scrawny, long-eared house cat, and that’s what I decided to call them. The Cat mantids are probably some of the largest in Africa, with the females’ body length approaching 20 cm. Males are about 15 cm long, which still makes for an imposing insect.

Despite his huge size, a Cat mantis (Heterochaeta orientalis) is virtually impossible to spot in its natural setting of bare branches in the woodland savanna of Gorongosa.

Despite his huge size, a Cat mantis is virtually impossible to spot in its natural setting of bare branches in the dry woodland savanna of Gorongosa.

Little is known about this species’ biology. I have always found Heterochaeta on tall shrubs and bushes in the woodland savanna, albeit finding them is definitely not easy – despite their size they are some of the most cryptic insects of Gorongosa. It is enough to take your eyes off an individual sitting on a branch for a few seconds to completely lose sense of its whereabouts. When resting on a branch these insects hold their long raptorial legs outstretched to the sides in an uncanny resemblance of two dead twigs coming off a larger branch, very unlike the typical “praying” stance of other mantids, who tend to hold their raptorial legs neatly folded under the pronotum. The pointy protuberances on the Cat mantis’ eyes enhance the illusion that this animal is just a dead, spiky stick. Clearly, their main defense mechanism is to remain undetected by either predator or prey.

While resting on a branch the Cat mantis keeps its forelegs outstretched to the side, enhancing the illusion of being just another dead stick.

While resting on a branch the Cat mantis keeps its forelegs outstretched to the side, enhancing the illusion of being just another dead stick.

But in addition to its superb crypsis the Cat mantis has another trick up its sleeve when it comes to avoiding being eaten. When I first tried to pick up one of the individuals that came to the light, it immediately responded by rearing up its body, opening the front legs to reveal a bright patch on the underside, and fanning its wings to flash a beautiful, contrastingly yellow and black pattern. This color combination signifies danger (think wasps and their stingers) and many potential predators may pause before attacking the Cat mantis, giving it time to fly away. The mantis is bluffing, of course, as other than a very weak pinch it can deliver with its long forelegs it does not have any real weapons or chemical defenses.

When cornered the Cat mantis rears up to make itself look bigger and flashes beautifully yellow and black hind wings that normally lie hidden under the cryptically colored front wings.

When cornered the Cat mantis rears up to make itself look bigger and flashes beautifully yellow and black hind wings that normally lie hidden under the cryptically colored front wings.

Ever since I first came to Mozambique I have been marveling at the praying mantis fauna of Gorongosa, which is the richest that I have seen anywhere in the world. My species list is approaching 50, but the actual number is almost certainly greater. Their abundance is also exceptionally high, and it is not rare for me to get 5-10 individuals of praying mantids in a single sweep of an insect net across the tall grassland. What drives this richness is something that I am interested in understanding, but it may be related to an equally high abundance of orthopteroid insects, the main prey item of many mantids.

A male Cat mantis at sunset.

A male Cat mantis at sunset.

Empusids

A portrait of a male empusid Idolomorpha dentifrons from Gorongosa National Park, Mozambique. This photo is a composite of four vertical frames.

A portrait of a male empusid Idolomorpha dentifrons from Gorongosa National Park, Mozambique. This photo is a composite of four vertical frames.

In about a week I should be back in Mozambique and this blog will likely get more interesting. We have an exciting project developing in Gorongosa National Park, one that is bound to generate a lot of good data and influence biodiversity science in the country for years to come. More about it soon. But in the meantime I thought I would put a spotlight on a relatively little known group of organisms that one can easily see in Mozambique – the empusid praying mantids.

The family Empusidae is a small lineage of mantids, with only 28 described species found mostly in drier regions of Africa and a handful of additional species in southern Europe and SE Asia. It is one of the very few families of mantids known to be monophyletic, and it shows – they all share remarkable morphology that makes them stand out among other members of this singular order of insects. Two main body types are common – they are either thin and stick-like or, while still being rather spindly, the body is covered with large lobes and flaps, making them excellent mimics of dried, shriveled leaves.

The stick-like variety, such as the genera Empusa, Hemiempusa, and Idolomorpha, are usually found in grassy vegetation, where they hunt small insects, such as planthoppers and grasshopper nymphs. Earlier this year I ran across a gorgeous male specimen of Idolomorpha dentifrons on the Cheringoma Plateau of Gorongosa, but had troubles photographing it in a way that would properly convey its incredibly elongate morphology. In the end I took a series of vertical photos of its head and front legs that I stitched together in PS, and here is the result. Male empusids are unusual in having pectinate antennae, the kind usually seen in silk moths and other insects with well-developed pheromonal communication, where the female emits sex pheromones and males follow the faint scent trail. Not surprisingly, such behavior was recently demonstrated to be present in empusids (Gemeno et al. 2005. J. Ins. Behav. 18: 389-403).

The leaf-like morphology can be seen in the Devil’s mantis (Idolomantis diabolica), arguably one of the most striking and beautiful praying mantids in the world. The body of immature individuals resembles a dry, withered leaf, except for the brighter colors on the underside of the raptorial front legs. Adults turn pale green and white, and the pattern on their front legs becomes brightly red, resembling vivid petals of a flower. There is a reason for this – Devil’s mantids are specialized hunters of pollinators, such as bees and butterflies, and presumably this bright coloration fools some insects into coming dangerously too close.

Devil’s mantids are known to occur in woodland savannas of Kenya and Tanzania, but on my recent visit to the National Natural History Museum in Maputo I discovered in its entomological collection a few ancient specimens from various parts of Mozambique. One had been collected in the 1960’s tantalizingly close to Gorongosa. Knowing that there is a chance of being able to see this gorgeous creature in its natural habitat, I am now obsessed with trying to find it. I didn’t succeed on my recent visit to Mozambique, but maybe I’ll have better luck this time. Watch this space.

Nymphs of the Devil's mantis (Idolomantis diabolica) resemble dry, shriveled leaves, which allows them to blend among the vegetation, where they hunt fast flying insects. Interestingly, this species is not interested in slower insects and those that walk or crawl on the vegetation – the prey must be flying really fast to elicit this predator's response. (This photo shows a captive individual.)

Nymphs of the Devil’s mantis (Idolomantis diabolica) resemble dry, shriveled leaves, which allows them to blend among the vegetation where they hunt flying insects. Interestingly, this species is not interested in slower insects and those that walk or crawl on the vegetation – the prey must be flying really fast to elicit this predator’s response. (This species has recently become popular in the pet trade, and this photo shows a captive individual.)

The Cape empusid mantis (Hemiempusa capensis) devouring a grasshopper.

The Cape empusid mantis (Hemiempusa capensis) from South Africa devouring a grasshopper.

Male empusid (I. dentifrons) cleaning his pectinate antennae.

Male empusid (I. dentifrons) cleaning his pectinate antennae.