Thursday, 3 August 2017

Spiny little farmers: the ant genus Polyrhachis in Zambia.

Of the many – very many – ants in Zambia, Polyrhachis are not only among the most conspicuous, but some of the most recogniseable – and, to my unending joy, there exist two open access, freely-downloadable keys to the genus within Africa, and – possibly because Polyrhachis are blessed with a great number of readily visible external features – these are (relatively) easy to read and easy to work through.



Polyrhachis schistacea is the most conspicuous and common Polyrhachis
in much of Zambia, and indeed much of sub-Saharan Africa


The first Polyrhachis to be encountered is almost always Polyrhachis schistacea, a very distinctive, ground-nesting species that is found almost everywhere. Although it probably absent from deep forest, it thrives even in dense, canopied woodland, and occasionally into wetter, riverine forest.

Between Bolton (1973)’s and Rigato (2016)’s reviews of the genus, five species are recorded from Zambia; a sixth species, P. schistacea, is also present throughout the country, and records from Zambia may have escaped mention simply because it is abundant almost everywhere.
With almost 500 species described globally, Polyrhachis is made more manageably by division into a number of subgenera – although all 61 species in sub-saharan Africa fall together into Polyrhachis (Myrma) – and species groups. Of the six species groups recorded from sub-saharan Africa, 2 are known to be present in Zambia, and a third occurs in a number of neighbouring countries and almost certainly extends into Zambia.

Polyrhachis epinotalis is a typical member of the militaris
species group, of which at least five species occur in Zambia.
Kundabwika, N. Province, Zambia. 








Polyrhachis weissi is the sole member of the
revoili species-group recorded from Zambia.
Chongwe, Lusaka Prov., Zambia. 


Although their (rather more speciose) cousins in the genus Camponotus often have not only major and minor workers – often requiring separate keys – butalso, sometimes, several grades between, Polyrhachis ants have only a single caste. Camponotus are also rather smooth-bodied, generic-looking ants, whose visible distinctions can be easy to miss; while the various Polyrhachis can have spines and ridges almost anywhere, making them a much easier group to work with.
                
Main body parts labelled for reference.
Polyrhachis epinotalis, Kundabwika, Zambia. 












Key to Species known or likely to occur within Zambia 
(brutalised into existence from the keys produced by Bolton (1973) and Rigato (2016)'s derived key)







11.    > Pronotum without a distinct margin, sides and dorsum joined by a smooth, uninterrupted curve (revoili group)(S., W., and Central Africa, including Zambia)………..........….Polyrhachis weissi
>     >>Pronotum at least with a partial margin, seen as a raised or projecting flange, ridge, or an acute angle separating dorsum from sides………………………………………….…......………...to 2

22.    >Metanotal groove indistinct, represented at most by a line scoring across the dorsum of alitrunk, which may or may not interrupt the sculpturation; never impressed, and sometimes undetectable (viscosa group)……………………………………………………………………......………to 3
>    >>With broad, impressed and distinct metanotal groove, in profile this may be seen as a V or U shaped trench separating mesonotum from propodeum (militaris group)…………….….….to 6
3
33.    >Gaster finely longitudinally striate (South Africa, Malawi)..…....……….Polyrhachis arnoldi
>>Gaster finely reticulate-punctate……………………………………….………………….to 4
4
44.       >Antennal scape broadened into a hood at tip, concealing base of following (first funicular) segment from above; the covered section of the first funicular segment is strongly flattened. Eyes generally flat, occasionally convex (widespread throughout Sub-Saharan Africa, from South Africa to Sudan and Ghana)…………………………………….……..........…………Polyrhachis viscosa>>Antennae not like this; eyes convex……………………………………………………...to 5
5
55.       >Ridge between spines of propodeum is raised medially into a distinct tooth or tubercle; the spines themselves curving distinctly upwards (East and Southern Africa) ..Polyrhachis wilmsi>>Ridge between spines of propodeum at most arched medially; the spines directed behind and to the side, curved only very slightly upwards (East and Southern Africa, and Angola)……................……………..…………………………………………………….……………Polyrhachis spinicola
66.       >Petiole with 2 spines………………………………………….........…………………….to 7
>>Petiole with 4 spines; the second pair may be reduced to small teeth………………...….to 8
7
77.       >Spines of petiole more-or-less parallel, strongly hooked backwards at the tips. Clypeus with carina, gaster (usually) with golden pubescence (West and Central Africa, south to D.R.C. and Angola)…………………………….…………………………….........………Polyrhachis laboriosa>>Spines of petiole diverging, curved backwards along their length but never hooked apically. Clypeus without carina; gaster usually with grey pubescence, never golden….Polyrhachis wellmani
8
88.       >Pronotum entirely without erect hairs dorsally (East and Southern Africa, from Kenya to Natal)………………………………………………………………………………..Polyrhachis schlueteri
>>Pronotum with erect hairs dorsally……………………………………………………….to 9
9
99.       >Dorsal surface of thorax without erect hairs except on the pronotum. Sides of head below eyes without erect hairs. Gaster polished, shining, only with very fine reticulation; pubescence short, diluted……………………………………………………………...………….Polyrhachis gagates
>>Dorsal surface of thorax with erect hairs on all segments; side of head below eyes with erect hairs. Gaster generally dull, with fine reticulate-punctulate sculpturing, or sculpturing hidden by pubescence………………………………………………………………………………….to 10

110.   >Pubescence sparse, not hiding sculpturation of alitrunk or gaster, usually greyish. Relatively narrow, slender species………………………………………..…………..Polyrhachis schistacea
>>Pubescence abundant everywhere, at least partially hiding sculpturation of dorsal alitrunk and gaster; generally golden…………………………………………………….……………..to 11
1
111.   >Head in full-face view rectangular; sides weakly convex, posterior corners always with distinct, more-or-less obtuse angles. Each eye with a blunt emargination behind, separating dorsum from sides. Propodeal spines short, tooth-like, curving upwards and much shorter than the depth of the propodeal declivity……………………………………..................…………Polyrhachis militaris
>>Head in full-face view oval, either without or with very faint corners behind; no margination of head behind eyes, sides and upperparts of head smoothly confluent. Propodeal spines long, upturned; as long as or almost as long as the depth of the declivity………………………………………………………………………Polyrhachis epinotalis


Bolton (1973) includes an overview of the habitats and habits of these species, as known at the time:

  • weissi constructs silk-and-debris nests under or between leaves in trees; it occupies a wide range of habitats from forest and veldt to savannah. 
  • arnoldi has been recorded nesting in tree hollows, protecting the nest with a matrix of silk and dirt. 
  • viscosa nests in sandy soil, usually in exposed sites; ants are primarily found foraging on the ground, but may also climb. It is largely restricted to savannahs and arid zones, but is also found coastally in Ghana. 
  • wilmsi nests in stem galls (in trees, I assume?)
  • spinicola has been recorded from acacia and citrus trees; its nesting habits are not clear. 
  • laboriosa is restricted to forested environments, where it builds a nest of twigs and leaf fragments, bound with silk and fungal hyphae, adhered to the undersides of leaves or built in the fork of tree branches; they aggressively defend the nest, spraying acid under their abdomens. Individuals disturbed are far less aggressive, usually simply dropping off their branches. 
  • Boston speculates that wellmani most likely has the same habits as the (very similar) schistacea, of which it may be a synonym. 
  • schlueteri is apparently restricted to hot, moist sites. 
  • gagates is a ground-nesting species, typically found in drier, open habitats such as savannah and semi-desert, only occasionally in scrub forest. The nests have been recorded at the bases of grasses, and under rocks; the entrance may be marked by a wide crater of dirt, or with a wall of woven material which extends into the entrance. 
  • schistacea is primarily a species of savannah and scrub forest, absent from rainforest; it nests in open ground or under stones or – rarely – decaying wood. They may construct a cup-like wall of grass-blades around the nest; they are also noted as a tender of hemipteran bugs. 
  • militaris is noted as an arboreal species of forests, especially rainforest; constructing a nest inside hollows of trunks and branches. Bolton does not separate epinotalis and militaris, so it is assumed here that epinotalis lives much the same life. 
Polyrhachis schistacea tending Membracid plant-hoppers in Mpongwe, Copperbelt, Zambia




References: 

1.       Bolton, B.  (1973). The ant genus Polyrhachis F. Smith in the Ethiopian Region (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History) Entomology 28 (5) pp. 283-369
2         2.       Rigato, F. (2016). The ant genus Polyrhachis F. Smith in sub-Saharan Africa, with
d                descriptions of ten new species. (Hymenoptera: Formicidae). Zootaxa 4088 (1) pp. 1-50



Tuesday, 6 December 2016

The Grasshopper without a name (Thericleidae)

The other day, on a group I follow on a popular social-networking site that shall not be named here, someone decided to complain about people answering queries with Latin names; while his initial complaint was mildly annoying, a later comment claimed that those using Latin names were snobbish and just trying to show off their own knowledge.

This is sufficiently absurd within the confines of the group itself, which covered snakes: snakes in the region do, for the most part, have unique common names; but many have multiple common names, which are not universal across their ranges, while the binomal names are universal; that's the entire point. The argument that they are elitist isn't new; the late, great ornithologist Levaillant was a firm believer that colloquial names were all you needed - but he was working with birds.

With insects, it is extremely unusual to find a species which has its very own common name. Sometimes, this applies to the entire family; take for example, this:

Thamithericles croceosignatus (Bolivar, 1914). Photographed in Chongwe District, Lusaka, Zambia; December 2013.

Not only does this colourful little creature not have a unique common name, its family doesn't; most often, they are referred to as Bush-hoppers, a name which also applies to a number of related families, and also some insects in completely separate orders.

The best that I can do (and will occasionally do for complainants on social-media) is find the English meaning of the name; but for that, see the (long-)previous post on a member of this family, Pseudothericles jallae (Griffini, 1897).

Fair warning: this post is about to turn into a tangled complaint about all sorts of things people and the media say; or things I think they say. 



You might - and people do - wonder why we should care about animals that have spent their entire histories so irrelevant to us that they don't even warrant names in Gosh-darned English.

First off, that's racist.

Look at this picture while you think about what you've done to deserve that. 



Harpethericles leechi, Descamps 1977, in New Kasama, South-East of Lusaka City. 






































Have you ever noticed that every single species of grasshopper in the UK has its very own common name? No? Well, they do. This might - in part - be down to how desperately few grasshoppers the UK has (13 members of suborder Caelifera - short-horned grasshoppers - native); but it also has a lot to do with occurring in Europe.

The Thericleidae - the family which we are currently looking at - do not occur in Europe, but are almost entirely limited to Africa.

This is not to say that Africa does not have a long tradition of naming; elderly villagers can have dozens of names for different creatures that the average European would dismiss at a glance as 'spiders', but many of these names have either disappeared or are disappearing - two well-spoken ladies recently racked their brains trying to find the word for butterfly for me after they dismissed the word 'gulugufe' as meaning something entirely different in Zambian Chewa and Nyanja as it means in Malawian Chewa; and despite both speaking several languages fluently, neither could produce a single word (In much the same way as 'Dumbledore' originally meant bumblebees (and occasionally stag beetles and cockchafers) in the UK, and became a term for a village idiot, 'gulugufe' seems to be primarily used in some areas to indicate a fool with no direction in life)

I am tempted, sometimes, to blame this loss of names indirectly on colonialism; even after independence, Zambia's first president, Kenneth Kaunda, resisted suggestion that local languages should be taught in Zambias schools for decades; believing that an entirely English-speaking population would be better equipped to thrive in a global economy. 

On the other hand, much of Sub-Saharan Africa only began writing down their language after the Europeans arrived; and with relatively small populations subject to the ravages of tribal conflict and the intra-African slave trade long before Ghana decided that gold was less profitable than slavery and launched the trans-Atlantic slave trade, keeping names for specific insects that are only occasionally encountered was probably not a priority in most areas.


Pseudothericles jallae jallae (Griffini, 1897) in
Lusaka South, February 2015. 




If this looks like an argument that they still shouldn't be a priority, that's because you're forgetting that tribal warfare and both the trans-Atlantic and intra-African slave-trades have mostly dried up. 

These days, more serious concerns are economic turbulence, voter dissatisfaction and - my personal favourite - environmental decline.

Aha, I hear you say; you have posted three images so far and not a one of them has wings! These creatures must be limited range endemics with narrow environmental tolerances!

How very insightful of you! Well, you've pre-empted my lengthy argument about how their limited ranges and particular taste where it comes to their living conditions mean that they exist on evolution's knife edge, depending on environmental consistency just to carry on existing.




Lophothericles euchore (Bolivar, 1914)
in Chongwe District, Lusaka, Zambia, February 2016.




And you can probably guess that I'm always happy to see them out and about, because they mean that the local environment is - over the broader area - stable. Needless to say, I don't really see them in the large farming blocks.

I do see some in the suburbs (especially Lophothericles euchore (Bolivar, 1914), left)










It also helps that - thanks to a truly fantastic monograph by Descamps (1977; sadly not available online but can be bought from NHBS for a painful price) - they are fairly identifiable.

But enough of this 'everything must be useful' nonsense. Personally, I think they're pretty awesome little creatures. For example, check out the 12 millimetre porcupine that is Uvaroviobia luanensis (Uvarov, 1953). 


Uvaroviobia luanensis (Uvarov, 1953), Chief Nyalugwe's area, Eastern Province, Zambia. 

You may notice the (Uvarov,1953) that follows its name? That's the author who described it, and the year it was described (and it's in brackets because Uvarov did not commit a terrible crime of nomenclatural impropriety and name a genus after himself; that change came later). In this particular case, the year it was described is also the only record of the species that I can find; recorded from the Luano valley - some distance from where I found it, but environmentally very similar - in 1953. 


You're looking at the male (above) by the way. The females look like this (below): 

Female Uvaroviobia luanensis (Uvarov, 1953)  on unnamed tributary of the Luangwa, Eastern Province, Zambia































Another U. luanensis...
Narrow-range endemic, so same area, too.





It's sexually dimorphic. Well, somewhat polymorphic; Females can sometimes also look like this (right): 

Lophothericles burri Descamps, 1977.
Female
In Chief Nyalugwe's area, Eastern Province










Lophothericles burri Descamps, 1977.
Male
In Chief Nyalugwe's area, Eastern Province


Uvarovobia's presence in a second valley system some distance from the site of its original description shows that it is much more widespread than previously thought, and may even extend in to Mozambique. This is even more likely for the larger, more typical Lophothericles burri Descamps, 1977, which co-occured in the same valley, barely a whistle away from the Mozambique border, and is more widely recorded within Zambia.
















They do get more widespread; Stenothericles porcellus (Miller, 1936), the prime suspect for a slightly troubling species from Chongwe (Lusaka), is recorded by Descamps from Malawi and Zimbabwe; curiously, he does not record it in Zambia at all. Of the two species of the genus that Descamps does record in Zambia, Stenothericles rossi Descamps, 1977 and S. zambiae Descamps, 1977, his illustrations of their cephalic (head) and thoracic (um... thorax) structures is quite different from both Stenothericles porcellus and my Chongwe Stenothericles; which might, then, be filling in a gap in an otherwise wide but disjunct distribution.



Stenothericles cf porcellus (Miller, 1936)
in Chongwe District, Lusaka, Zambia, December '13


For those of you who can't bring themselves to fork out for Descamps' Monograph - and I'm not judging you, I know that it can be hard to justify spending money on animals that you will likely never see, even if you are on the right continent - the best free resource on these and any other common-name-less Tsokonombwe (Chewa - Grasshopper) that you happen to be interested in is probably the Orthoptera Species File.

Saturday, 3 December 2016

The Thick-Headed Flies - Conopidae


A rather larger - and much more confusing - family than last month's Micropezids, meet the Thick Headed Flies:
Conops (unidentified species) in Chongwe District, Lusaka, Zambia; February 2013.






























These colourful, wasp-like flies have had a tumultous taxonomic history; bouncing between the Aschiza (along with Hoverflies such as Metadon inermis) and the Schizophora (along with the greatest diversity of modern flies, including such oddities as the Stalk-Eyed Diasemopsis meigenii), but while genetics support its relationship to the Schizophora, its position therein remains imperfectly resolved (Gibson et al, 2010); but the family itself has been quite intensely studied (e.g. Gibson and Skevington, 2013).
Sicus ferrugineus Scopoli, 1763,
in Chichester, West Sussex, UK; July 2013.





Their life-habits are fairly remarkable, too; while adults are often found visiting flowers, they spend their larval stages eating other insects - usually bees (as is the case with Sicus ferrugineus Scopoli,1763 from the UK) or wasps of various families; a few species are known to parasitize cockroaches and crickets.








Wasps and bees are by no means an easy target for a fly with a limited physical arsenal; no powerful sting, no heavily-built, piercing mouthparts (which would be somewhat counterproductive, at any rate); and so many get around this problem by looking remarkably wasp-like:

Archiconops pseudoerythrocephalus Stuke, 2004 on banks of Luangwa; Eastern Province, Zambia, April 2015. 




Unidentified Mammoth Wasp (Scoliidae) from Lusaka,
showing similarity of appearance to that of Archiconops
The above Archiconops was closely following a Mammoth-Wasp (family Scoliidae), which itself was probably an external parasitoid of larval Scarab beetles; although Scoliids - unlike may parasitoid wasps - can sting, Archiconops is likely given some protection by its resemblance, allowing it to get close enough to use its scimilar-like ovipositor to rapidly lay an egg between the wasp's thorax and abdomen, and its agility - much greater than the often-bumbling Scoliids - allows it to beat a hasty retreat as soon as the wasp catches on.



 But there are other risks to hyperparasitism; evolutionary risks. While the wasp's populations are at the mercy of fluctuations in beetle populations, and must remain at a relatively low level to ensure that they do not begin to exhaust their host populations, the fly's survival depends both on the wasp and on the beetle, and if either of them has a bad year, the fly's population will plummet - and with reproductive rates necessarily low to avoid causing a crash in host populations, they can take generations to recover, and are rarely - if ever - common.

Conops cf aurantius Brunetti, 1925 in garden in Chongwe, Lusaka, Zambia;
only a handful of these flies will be seen per year even in most rural environments. 


Identification can also prove surprisingly complicated; although the flies are very distinctive as far as flies go - even if they may, at a glance, they may be mistaken for the wasps they mimic - there are a precious few others that can be strikingly similar.


Systropus Weidemann, 1820, is a wasp-mimicking bee-fly (family Bombyliidae)
that can bear a striking resemblance to some Conopids. Chongwe, February 2016. 

Physocephala rufipes (Fabricius, 1781)
in Bosham, West Sussex, UK

The fly immediately above is a Zambian example of Systropus Weidemann 1820, an unusual genus of Bee-flies (Bombyliidae) which, like most Conopids, closely mimics wasps. Physocephala - a very widespread genus of Conopid that also occurs in the region  (although the species shown is the British Physocephala rufipes (Fabricius, 1781)) - can be very similar; and they are probably most easily distinguished by their eyes; in Conopids, these are always widely separated, while in Systropus, they meet at the top of the head.





There are numerous other distinctions, particularly in the dramatic external genitalia of many female Conopids; but the widely separated eyes are a very prominent feature of the Conopids, and help to mark out this (un-cooperative) Conops cf elegans Meigen, 1824 as a member of the family [NB - various flies in various families ALSO have widely separated eyes, but are not nearly so Conopid-looking as Systropus].

Conops cf elegans, Meigen 1824.
Banks of the Luangwa River, Eastern Province, Zambia, April 2015.  

And just to be going with, the European Conops quadrifasciatus De Geer,1776 in a West-Sussex Garden. Although this species was only formally described some 18 years after Linnaeus' Systema Naturae transformed entomology in 1758, the genus - which we have encountered almost throughout this post - is actually one of the first described of all invertebrate genera*, as one of only 10 genera of flies that Linnaeus actually described.

Conops quadrifasciatus De Geer,1776 in Bosham, West Sussex, UK; August 2013.



More details about Conopid life-histories can be read in Gibson's 2011 thesis on the family, which is (unlike the other two Gibson papers) freely available online. 

A good starting place for Conopids in Southern Africa is O. Kröber's The Conopidae of South Africa, in Volume 14 Annals of the Transvaal Museum; this is a very elderly paper, however, and it is always worth checking on the Diptera Nomenclator that the names Kröber uses are still appropriate to species in south Africa (e.g. Conops erythrocephala Fabricius, 1794 in Kröber's work almost certainly refers to Archiconops pseudoerythrocephalus Stuke, 2004)



*Incidentally, and as I was completely mis-explaining to a much-more-knowledgeable entomologist the other day (As a general rule, if I'm trying to explain something genuinely interesting to someone cleverer than me who doesn't know about it, I will forget everything that is inside my head and be embarassingly wrong about everything), Linnaeus Conops - and all his other invertebrate genera - lag behind several European spiders. Although no longer in its original genus, Enoplognatha ovata (Clerck, 1757) - the very first post on this blog - is one of those species which is still listed as being described one year before Linnaeus' Systema naturae, which is officially considered the starting-gun for the binomial naming system in invertebrates - to avoid taxonomists having to trawl through Pliny and older works to see who deserves the truly initial credit, so the whole thing is a bit of a scandal. 

Tuesday, 29 November 2016

Silky Lacewings (Psychopsidae)

I spend a lot of time trying to explain to people just how mind-numbingly diverse invertebrates can be.

And they are; take the lacewings - quite small, as insect orders* go, but still have over 600 species recorded from Zambia or a neighbouring country (based on information from the Lacewing Digital Library, an excellent resource that I probably rely on far too heavily).

So it's always pleasing to realise that I have encountered every member of a specific clade that enters the country, whether it's all the subspecies of a species, all the species of a genus or - in this case - all the members of the family.

Even if that family is the Psychopsidae, one of the least represented Neuropteran families in the continent with only eight species entering Africa, and only two likely to occur in Zambia (i.e. recorded in Zambia, or in multiple disjunct, bordering countries, in areas of comparable climate.

Before I bore you too much with endless text, here's one of them:

Silveira marshalli (McLachlan, 1902); came to lights on an unnamed tributary of the Luangwa. 

These eight species in three genera are actually a rather hefty share of the global diversity; both Australia and Asia have only a single genus each (although Australia's Psychopsis contains half of the global species).

They are extremely distinctive lacewings, at least within the region, instantly separated from all other lacewings by their broad, hairy wings; while some 'green' lacewings (Chrysopidae) and the Osmylids (no common name) are rather broad shouldered, none are quite so dramatic as these; they also tend to have rather longer antennae, and their bodies extend more noticeably in front of the wings.

Most are associated with woodland, where they have been suspected to pre-powder their eggs with vegetable matter, and fire them into leaf-litter while in flight (for more on that - and a general overview of the family - see Oswald, 1993); these presumably hatch into the usual, hyper-predatory little monsters that lacewing larvae usually are.

Formally, only one species is recorded from Zambia; but given that Zambia's predominant natural habitat is Miombo woodland (accounts vary as to whether this is a fire-dominated moist savannah, or is a type of subtropical deciduous forest currently massively degraded by man-made fires), it wasn't a stretch to assume that Silveira marshalli (McLachlan, 1902) - recorded from Botswana, Zimbabwe, South Africa and Zaire - would be present; it to lights in numbers in forested parts of Eastern province.

As for the other, Zygophlebius leoninas, Navás, 1910 - easily the most widespread African species, probably the most widespread species in the entire family (although as you can read in Oswald, 1994, there is a bit of a mess where it comes to records of this and the genitally-distinguished Z. zebra (Brauer, 1899) - I'd really like to be able to credit its appearance at a kitchen window in the increasingly developed Chongwe district to my ongoing tree-planting (and native-tree-encouraging) efforts, rather than the more likely conclusion that it's just another species that is slowly disappearing as every acre of ground is agriculturally exhausted and covered in concrete.

On that somewhat bleak note, here it is:


Zygophlebius leoninus Navás, 1910 in Chongwe District, Lusaka, Zambia. 





















*Main taxonomic rankings, in order from largest to smallest: Domain (e.g. Eukaryota); Kingdom (e.g. Animalia); Phylum, (e.g. Arthropoda); Class (e.g. Insecta); Order (e.g. Neuroptera - lacewings); Family (e.g. Psychopsidae - Silky Lacewings); Genus (e.g. Silveira or Zygophlebius) and Species (e.g. Silveira marshalli)

**Yes, I pluralise words that end in 'x' with 'ces'. Sue me. 

Wednesday, 23 November 2016

The Stilt-Legged Flies - Micropezidae

Flies.

True flies, to be specific; the two-winged members of the order Diptera  - I feel like we've neglected them a little*. They are, after all, the second largest order of insects in terms of described species, and - as I'm currently trying to come up with a rough key to the families of flies in Zambia, I'm currently painfully aware of just how diverse they are.

Based on recorded distributions of the 159 or so fly families globally (some are sometimes subsumed, there should be some 100 - not roughly, that is actually the number - families of flies present in Zambia.

Note that that isn't 100 'types' of flies, or 100 'species' of flies, but 100 families of true flies; some of which contain hundreds of known species in the region, some of which are only separable by dissection of the genitalia (ow) - and this may only represent a fraction of the actual diversity of this (understudied) country.

As you might imagine, these can be a nightmare to identify - even in groups where species are physically very different, because many taxonomists of history were so concerned with minute differences of genitalia that they neglected to mention the massive external differences between related genera and species (this is essentially why we have voucher specimens and museums: so that authors who think one feature is the most important don't end up making a taxonomic group completely unworkable. It doesn't always work).

Many of these 100 families, however, have only a few species in the region: while there are several dozen species further North in the continent, Southern Africa hosts only six species of the family Micropezidae, and records indicate that Zambia hosts even fewer.

To interrupt this long block of text, here's one of them: 

Mimegralla, probably Mimegralla fuelleborni (Enderlein, 1922, photographed on a farm outside of Mazabuka. 





You'd think with so few species, we'd know just what they do with their daily lives.

We do know a little, but the trouble with these flies is that they are fairly small and inconspicuous, and rarely - if ever - common, so that even with only six (known) species in the entirely of Africa below the Zambezi, the most insightful observation that the-usually-helpful Barraclough** made into their life histories was that their curious white fore-limbs could to be some sort of imitation of ichneumon wasps. Quite how it would benefit the fly to imitate a wasp which cannot sting remains unclear.

As to the rest? Well, one Indian species (Mimegralla coerulifrons (Macquart, 1843)) is a pest in commercial ginger and turmeric farming, and as a result has been quite well studied, and adults have been variously stated to be predatory (which, although this particular species location and behaviour suggested that it was there for the aphids, is doubtful applied across the entire family), and the suggestion that larvae are saprophagous (same link as the last, even though I should chase it the source, I know).

And if we throw in anecdotal claims, it gets even more confusing.

So let's not. Let's just enjoy them.

Here's another, this time Erythromyiella rufa (Hennig, 1935) from Lusaka South:





And, well, at some point I must learn how to write some sort of conclusion to these things instead of just trailing off..










*Not entirely - we have covered a few before - a long, long, long time ago: a rather unusual 'flesh fly' -  Dolichotachina caudata - which probably, like its closest well-studied relatives, acts as a cuckoo to burrow-nesting wasps; the extraorinary long-horned cranefly 
Megistocera filipes, never previously recorded in Zambia; the bizarre Stalk-eyed Diasemopsis meigenii, four hoverflies all trying - with varying success, to convince us that they are wasps or bees (Senaspis haemorrhoaHelophilus pendulusEpisyrphus balteatus and Metadon inermis), and the inexplicably named 'centurion' Chloromyia formosa


**If you are interested in Micropezidae south of the Zambezi and Kunene rivers (i.e. Zimbabwe, Botswana, South Africa, Southern Mozambique and probably-not-Namibia-because-they-are-mostly-forest-associated, do download the Barraclough (1996) paper, as it contains descriptions of all 6 regional species, and a decent key. I suspect that in the Northern parts of Zambia, Mozambique and Malawi, we get a few more recently-described (or undescribed) species - Tanzania certainly does - but for Southern Africa, this seems to be your lot. 

Monday, 14 November 2016

The Net Casting Spiders (Deinopidae)

Meet Deinopis Macleay, 1839. 

Male. Photographed in Chongwe District, Lusaka Prov., Zambia, November 2016, using Olympus E-420 and 3 KOOD lenses. 

Deinopis is the more iconic of the two genera of Net-Casting Spiders, distributed throughout the warmer regions of the world; it lends its name to their family (Deinopidae), and is the source of another common name for the family - Ogre-faced Spiders - and, locally at least, species of this genus are physically much larger, and difficult to overlook. This impressive male, found wandering on a driveway on a hot, humid night, had legs that spanned over 5cm.





To put this in context, his legs are very long; unusually long, you might think (if you are used to thinking about these things) for a spider that neither lives in caves (where anything and everything has a license to have very long legs) or live in a web





But this little Kangaude (Chewa - spider) does build a web. To those who know a little about spiders, this doesn't really resolve much: while his legs make slightly more sense, now, his eyes become something of a puzzle: of the other spiders blessed with such large and conspicuous peepers, most belong to either the Jumping Spiders (family Salticidae) or the Wolf Spiders (family Lycosidae); the vast majority of which are active, free-living predators, which use their eyes to see, hunt and capture prey - or, in the case of most jumping spiders - to communicate via semaphore.

To explain all of this, we have to turn to Deinopis' smaller and more abundant relative - and the only other genus in the family - Menneus Simon, 1876 - for a practical demonstration: 


Photographed in Chongwe, Lusaka, Zambia in April 2015. 

As already mentioned, one of the common names for this family of spider is Net-Casting Spider (and I will eventually find the direct Chewa translation for that, in theory); and they do precisely that; they wander around in search of a crossing point of nocturnal insects to wander through, and then, suspended above it by a simple thread, they spin an entire web between their (very long) front legs, and they wait.

And they wait.

Eventually something wanders past, and, seeing the movement, they whip down the net and voila, pre-wrapped meal - and a unique method of hunting that needs both a web and excellent vision.
Menneus - note the smaller eyes and the abdominal 'hump'. 




It is worth noting that Menneus' vision isn't quite like Deinopis'; they are probably most easily identified, in fact, by lacking the massive enlargement of the posterior median eyes seen in Deinopis; their eyes are still larger, on the whole, than those of most web-spinning spiders, but if it wasn't for their extraordinary webs, and the curious protuberances from their abdomen (earning them the alternative names of Camel-backed Spiders and Hump-Backed Spiders), they might be mistaken for free-living nursery-web spiders (family Pisauridae). 













Although identification to genus for this family is extremely easy - especially now that Avella and Avellopsis have been shoehorned into Menneus - you'll notice that I haven't listed a species name for either of our two guest-stars; although none appear to be recorded specifically from Zambia, a number of species are recorded from neighbouring countries and the wider region (see the World Spider Catalog page on the family); and - as the spiders are inconspicuous, nocturnal and easily overlooked - there is every chance that these do not belong to described species at all.

So I'll get back to you on that.