The Myrmeleontiform Lacewings (Neuroptera), OR No, it's not a weird dragonfly OR Insects and Agriculture part I of... many.

Palpares normalis Navás, 1911 (Neuroptera: Myrmeleontidae) in dry wooded slopes in the Mutinondo Wilderness Area, Muchinga Province, Zambia

So. 

    A while back I was very excited that the EU had issued a broad, long overdue ban on Neonicotinoid pesticides in Europe. 
This ban was not quite the starting gun for improved awareness of the value and increasing plight of insect communities that I might have hoped. 
    I recognise that the seeming progress created by the recent media coverage (here, there and everywhere) and UN Report on the matter may end up Anita Hill'd for a good twenty years, but here and now, I want to try to be positive. 

So

    I have an evil plan to save the world.
    Well, an evil plan to help people reduce their active efforts to unwittingly destroy the world, and give them an opportunity to give the world a little more opportunity to save itself. 

So 

    The next few posts are intended to focus on the roles that insects of different groups play in agriculture, something that I know from far more experience than I'd like is dangerously simplified by the public at large, even when the idea of a beneficial insect is actually floating around inside the heads of the farmers, farm managers, scouts, labourers et al.
    The plan is to rotate through an order of insects each month, using broad strokes to explain the roles and interactions between different groups. Because June is very nearly over, I'm going to start with a fairly small group that can be quite easily chunked into two (or three at the most) posts, beginning with a subgroup that can be very conspicuous, but aren't going to win any prizes for the mass of their impact: 

The Myrmeleontiform Lacewings
or 

No, it's not a weird dragonfly

The weirdly wonderful, and somewhat atypical, Cymothales sp. (Neuroptera: Myrmeleontidae) coming to lights in Chongwe, Lusaka Province, Zambia. Compare to the similarly odd and oddly similar Tmesibasis (Neuroptera: Ascalaphidae) further down. 

The suborder Myrmeleontiformia is one of two suborders usually included in the weird and wonderful - if rather small - order Neuroptera, and for the most part, if a non-enthusiast walking along would stop and go "Wow" at a lacewing, it's probably in this suborder. Probably.

If I was a paleontologist, which I'm not, the picture would be complicated by numerous long extinct (probably not because of humans) families. However, from where I sit, the Myrmeleontiforms are split into: 

Superfamily Myrmeleontoidea, which contains:

• Family Myrmeleontidae, the Antlions
• Family Ascalaphidae, the Owlflies (sometimes merged into Myrmeleontidae)
  and
• Family Nymphidae, the Split-Foot Lacewings (Essentially the last survivors of a much more diverse, largely extinct group of lacewings. Mostly in Australasia, some to eastern Asia, none in Africa, which is probably good because I had to google them to be sure that they were actually Myrmeleontiform. We will not be discussing them any further today)

Superfamily Nemopteroidea, which is made up of:

• Family Nemopteridae - Ribbon-Wing and Spoon-Wing Lacewings
• Family Psychopsidae - the Moth Lacewings

It's not a coincidence that I listed the Myrmeleontidae first: they are almost universally the most abundant, and very much the most important, of any of these families, and we will therefore be discussing them first:


Ant-Lions of family Myrmeleontidae

Myrmeleon lethifer Walker, 1853, in woodland in the Mutinondo Wilderness Area, Muchinga Province, Zambia. 

Hagenomyia tristis (Walker, 1853) in woodland edge
 MutinondoWilderness Area, Muchinga Province, Zambia. 

The direct effects of these lacewings on agriculture are... not huge. Although they are the most abundant large lacewings, most species are still generally uncommon where they occur, and a diverse mix of species is probably more useful as an indicator of a healthy habitat than directly beneficial to the human users of that habitat. So, as a quick break-down for farmers:

Macroleon quinquemaculatus (Hagen, 1853) coming to
lights in  Chongwe, Lusaka Province, Zambia

Problems:

None. They don't damage crops or pester livestock, and where insects like fungus gnats also don't care about your crops or livestock but damage roots and spread diseases through sheer numbers, the most abundant lacewings just aren't numerous enough to do damage.

Benefits:

Macronemurus sp. in dry woodland near Chilinga,
Eastern Province, Zambia

Pollination? Nope. I have my suspicion that genera such as Cymothales visit flowers while I'm not looking, but even if they spent all day fluttering between flowers, their natural populations are just too low to be effective pollinators.







Pest Control? A resounding YES. While all
species are predatory as larvae and predatory (or
non-feeding) as adults, it is really only a
handful of gregarious species like Hagenomyia tristis 
and Myrmeleon lethifer which ever reach the densities

Banyutus sp. coming to lights in Chongwe,
Lusaka Province, Zambia.

 needed to make any dent in the populations of unwelcome insects such as mosquitoes, fungus gnats 
and other weak-flying small insects. The larvae of
Hagenomyia and Myrmeleon are also a factor in
limiting movement of ants, termites and other small,
terrestrial insects - but most people who've spent any
time at all on any farm in Zambia will already have borne witness to an ant being dragged to a horror-
movie style ending by the large, sickle-shaped jaws emerging from the bottom of a conical pit...
Hagenomyia in particular forms dense aggregations of these tiny death-traps in sandy soils, which, while in
 itself not controlling ant or termite populations,
offers just one of the many angles of attack to keep
 them from taking over the world. Which is nice!

Neuroleon distinctus (Navás, 1931) in woodland edge in
Mutinondo Wilderness Area, Muchinga Provinca, 
Zambia.

And now for the post-amble: What, Where and Why Care? 

As much as they are not (at all) closely related,
Antlions are basically the dry-land alternative to dragonflies: The larvae are horror-movie 
monsters that just happen to torment other 
invertebrates instead of college-
students/babysitters/other assorted collections of industry-standard attractive people who make bad decisions and the adults are aerial predators that flit around in the undergrowth murdering all and sundry smaller insects that don't get out of their way. So... NOT weird dragonflies but they do act quite a lot like it.

Not only do they not depend on water, but most

Centroclisis sp. coming to lights in Chongwe,
Lusaka Province, Zambia.

groups actively require its absence for at least part
of their development: the steep sides of their iconic conical pits are a bit useless as an insect trap if they
are waterlogged and the ant can just walk out calmly
while the jaws of death throw mud-pies ineffectively around them. In wetter areas, pit-building antlions are
relegated to rain-shadows (which means that they are
often quite fond of the sandy areas under the eaves of houses - if only people would spend less time dousing these areas with insecticides, they might spawn huge numbers of natural born mosquito killers), and you tend to find more of the tree-hole dwelling Centroclisis.
In arid areas and on well-drained slopes, the striking Palpares become common; their larvae are
less industrious, and - as with many, many other
antlions - essentially swim through the sand in search
of anyone else to eat. 

Palparellus nyassanus (Navas, 1911) in dry scrub in
Livingstone, Southern Province, (Barotseland) Zambia. 

As much as any individual Antlion is basically a
 killing machine, their effects on populations of
smaller insects are probably not overwhelming.
However, where vertebrate ecosystems maintain
stability by having just a few, often territorial
predators, stability in invertebrate populations
instead relies on a vast network of different
predators and parasites - so if one predator's
 population has a bad year, prey species are kept
 in check by another.*

Another value, particularly to environmental researchers, is that these animals are excellent indicators: most are incredibly specialist in their breeding preferences (once more, I should add except Hagenomyia tristis), and are among the first to disappear entirely from fragmented habitats. First, and it astonishes me that there is not a lot more focus on lacewing groups during impact assessments as a result, animals whose numbers are naturally low tend to suffer disproportionately from something called Allee Effects, which we will discuss in our next group, the Owlflies.

Palpares cataractae Péringuey, 1910, on pseudo-arid
grassland slopes in Kundabwika falls Heritage site,
Northern Province, Zambia

Palpares schoutedeni Navás, 1925, in dry woodland on the
west bank of Kundabwika falls, Luapula Province, Zambia

Owlflies of family Ascalaphidae

The wonderfully weird Tmesibasis lacerata (Hagen, 1853) in woodland in the Mutinondo Wilderness Area,
Muchinga Province, Zambia. 

Problems: None (See above). 

Benefits: 

Pollination: No
Pest Control: No

So, farmers. The key thing to remember is that these insects are not your enemy. That said, the chances of you meeting any of them are... rather low. So on to the amble: 

What, Where and Why Care?

If Antlions are naturally uncommon, Owlflies are naturally scarce. They overlap broadly, but where Antlions are most abundant in open, arid environments, the owlflies tend to be more numerous (well, less completely absent) in wooded areas, where their young hunt for their victims much more actively, usually on tree-trunks and in leaf-litter. I personally find the larvae quite appealing, as murderous little fiends go, but I felt maternal watching a rat tapeworm (Hymenolepis) emerge from its cyst under a microscope, so my opinion on these matters does not count. The adults are broadly similar to antlions, but tend to be much more wary, and rather stronger fliers - a similar difference as you'd see between ancient Norsemen hunting whales from long-boats using spears and their 20th century descendants going out on a motorized rig with a harpoon gun.

Another difference is that they are never common. This isn't simply because their favoured habitats are under intense pressure in this part of the world** - they just seem to have naturally low population densities. 

Allocormodes junodi van der Weele, 1909, in woodland in
Mutinondo Wilderness Area, Muchinga Province, Zambia. 

And this is where I get to talk about Allee Effects. Yay!

We're going to start with an analogy. We'll use people, because I'm told other people find them easier to relate to than Pyrenean Ibex, which we'll come back to later. We're going to start with a nice, average sample. 

Our imaginary, average sample of adult humans comprises 50 females and 50 males - well, almost (in most places, male embryos are less viable, and men tend to die younger).

Now say that this average sample of produces 100 offspring over their lifetimes, but instead of being nice and average, this sample is truly random; let's say that there are 61 males and 39 females. No big, right? Across the whole of our seven-point-something-billion-strong species there are enough babies being born to account for the shortage of females - no worries.

But what if those 50 men and 50 women were the only people?

Well, now it is a problem. We went from having 50

Ascalaphus festivus (Rambur, 1842) in grassland
in Chongwe, Lusaka, Zambia

 women, who produce an average of 2 children each
 in a generation, to having 39, who will probably
also produce an average of 2 children each (sorry,
males, but except in species like seahorses and
cardinalfish, you really don't matter when it comes to population dynamics).

So our third generation is comprised of just 78 people. Let's not even pretend that the law of averages is anything but a logical fallacy, and just accept that there is no improved chance of female offspring in this generation just because we had a shortage in the last one. We're looking at 50-50 odds, which means that, all things being equal, this is our new population size.

Now what if, by random chance, this third generation just happens to be low in females again? If out of 78, only 35 are female? Well, look at that, our population size just fell again.

And sure, any one of these generations could, by random chance, be overwhelmingly female, and then our population would go up again, but the point here is that chaos is unpredictable, and if we were to repeat our experiment enough times, we would find plenty of iterations where random chance
eventually produces an all-male generation and,
for reasons that should be obvious, that is the

Disparomitus longus Navás, 1911 in riparian forest below
Kabwelume falls, near Mporokoso, Northern Province, Zambia

end of that.

AND THEN lets give our imaginary population genetics. By chance, they might end up like the Eurasian Beaver, which managed to shed almost all its genetic weaknesses over generations of dwindling populations and inbreeding and can build a healthy, thriving population from just three individuals (eurgh), or more likely, generations upon generations of inbreeding means that every mating produces a larger proportion non-viable embryos or sickly offspring. This is even worse if our population of 100 are not mixing freely, but are spread out over their habitat, where they quickly become more likely to meet and mate with a relative than a non-relative.

Encyoposis seydeli (Navás, 1929) in dry woodland in
Mutinondo Wilderness Area, Muchinga Province, Zambia. 

AS IF THAT'S NOT ENOUGH, let's give them an environment. Say, for example, that they live in a forest where once a year a tree falls on someone, killing them****. The chances of this happening in a year where, by extremely bad luck, you're down to one female, AND it happening to that one female, are extremely remote, right?

Right. But random chance is random chance, and Celia, the last wild Bucardo (Capra pyreniaca pyreniaca - I told you we'd come back to the Pyrenean Ibex) got squished by a falling tree and her subspecies went extinct. Najin and Fatu, the last two female Northern White Rhinos (Ceratotherium simum cottoni) in the world have bad hips and a damaged uterus between them which render them both functionally infertile - even if the last male wasn't dead.


You get the picture. 

Now, imagine that we go back to seven billion people in the world. But for some reason - let's say, for example, scorching deserts that anyone who tries to cross dies - they are split into populations of an average size of... 100.

Remember this guy? Eremoides bicristatus (Banks, 1924)
 in grassland in Chongwe district, Lusaka, Zambia. 

In any given generation, about half of those populations will get more females than the generation before. About half will get less. Do you see where this is going?

This species is doomed. DOOMED, I say. DOOOOOOMED. :)

Each generation is tossing a coin for everything it has: half the time, they win, and the population increases a little, and they toss the coin again. Half the time, they lose, and then they do not toss the coin again. 

In a connected species, you can spread your winnings out, and toss the coin again even if you lost there, because you won somewhere else.

Enough analogies? Good. 

Because we are fragmenting other animals' populations without even knowing it. Cities, fields, roads, firebreaks, even footpaths present an impassable or near-impassable barrier to some species, and as our populations expand into more and more of the planet, environmental specialists find the parts of the planet that they can live in get
smaller and smaller as well as more and more
 isolated. This is the reason that there are constant
campaigns for corridor areas connecting national

Phalascusa cf. vassei van der Weele, 1909 in riverine
vegetation near Chilinga, Eastern Province, Zambia. 

parks - to let lions and tigers and elephants and pandas move around more freely, and to create a single, large, freely mixing population rather than dozens or more of tiny, fragmented ones. 

And owlflies?

A large area doesn't support many. Like large mammals.

Unlike most large mammals, they breed fairly fast - for most species, a generation is a year or a season. So their generations pass fast. As a result, like the proverbial canary in the coalmine (YES, another analogy, and this one's a cliché, too), the absence of their populations in apparently suitable habitats is an early warning sign that something has gone wrong and, whether it is obvious or not, something has happened to break up the interconnected metapopulations that are needed to keep the species going, into isolated, vulnerable populations that disappear on a coin-toss, and they let us know of that before the ecologically dominant species that keep the system functioning also disappear, and therefore give us a window of time and a sliver of  chance to do something about it.

So that's owlflies (and also Allee effects and why we really should be much, much, much, much, much, much, much, much, much, much, much, much, much, much, much, much, much, much, much more concerned about the loss and fragmentation of natural habitats than we are). Depressed? Good. Because the next group is fun to look at and I don't have very much to say about them beyond that. 

Spoonwing Lacewings of family Nemopteridae

Nemeura glauningii (Kolbe, 1901) above Kundabwika falls in Northern Province, Zambia. 

Farmer's summary: 

Problems:

Probably None.
Benefits: 

Pollination: yes, probably - the adults seem to feed almost exclusively on pollen, but by virtue of being... not common, they probably aren't as effective at pollinating crops as... well, almost anything. 

Pest Control: Possibly? They may or may not feed on ants in the larval stage - although the lack of clarity is beautifully illustrated by Popov's note (near the end) that they might eat ants because he didn't see them eat anything he offered them. Which demonstrates about how enigmatic these insects are. 

What, Where and Why Care?

Bizarre, long-winged insects that only seem to approach numbers resembling "common" in arid or (in Zambia) pseudo-arid areas of well-drained sandy soils. The adults are probably pollen-feeding (which is pretty much the standard for all non-predatory lacewing adults) and the larvae are... well, they burrow. And they drink liquids. Really, my knowledge on this subject is less than Popov's (remember, when reading his bafflement and speculation, that Popov is a name that pops up all over the world wherever lacewings are mentioned). 

As to why care? Intellectually, I don't have anything new to say here: species richness creates stability, naturally rare insects offer an early-warning system for trouble in ecosystems. However, subjectively, I will say that they are wonderfully weird, and I like that they exist. 

And last, but not... well, yes, they actually are least in many ways, 

Silky Lacewings of family Psychopsidae

Zygophlebius leoninus Navás, 1910 in miombo woodland in Mutinondo Wilderness Area, Muchinga Province, Zambia

Well, they are the least showy, the least understood and (globally, and probably Zambia, at least, where we probably have at least 3 species of Spoonwing) the least speciose. I've already said as much as I know about this family in this post celebrating them specifically.

To farmers: of these enigmatic little wierdos, all I can say is that if they're in your crop, you don't need to panic - they won't be for long. Their populations are closely tied to woodland and forest with a healthy leaf-litter layer - and when that is cleared for farming, their populations dwindle and disappear in fairly short order.

Silveira marshalli (McLachlan, 1902) coming to lights in the
Mutinondo Wilderness Area, Muchinga Province, Zambia. 

With that said, earlier this year, Zygophlebius leoninus Navás, 1910 became for several weeks easily the most abundant adult lacewing in the woodland of my current workplace, and indeed the most conspicuous large insect around. Part of that was probably the bad luck of other species: poorly timed torrential rain depressed many species this season in a way that Prozac just won't help, and Zygophlebius was among the few large insects that was apparently unaffected (in an alliterative twist, the other species vying for most conspicuously common insect in the woodland was Zonocerus elegans, the Mnunkhadala/Elegant Locust).

So...

Are we done? It seems like we've made it through! Well, you have. At the point that I wrote this, I still had to choose, edit and caption the photographs which I'm sure made this lengthy text much more digestible. Come back... soon, when we'll cover much more briefly the (generally) less showy lacewings currently lumped into the suborder Hemerobiiformia. I'll try not to spend too much time on the weird-looking species at the expense of the economically useful ones. And I'll probably speculate as to why they are all lumped into a clearly paraphyletic suborder. 

Recommended Reading

Identification of these groups is... troublesome, but between the virtual museum and the Tervuren Museum's illustrated database you will find reliably identified photographs of many African species to set you off in roughly the right direction. As ever, the lacewing digital library is a (less user-unfriendly than it used to be, or I'm just getting used to it) fantastic resource in which you can find ranges, dates of description and most of the literature in which these species are described and discussed. For a fairly casual overview of just how awesome and terrifying the Myrmeleontidae in particular are, I'd recommend downloading Mansell's Evolution and success of antlions (Neuropterida: Neuroptera: Myrmeleontidae), from Stapfia vol. 60 (Zobodat link). If you can get your hands on a copy of Tjeder & Hansson's 1992 monograph on the African Ascalaphidae, be aware that Bo Tjeder's death left it painfully incomplete - it is still useful, but full of gaps. 

*This may seem like a cop-out - that something may not be the keystone to a functioning ecosystem, but still be important to the functions of that system - but as a practical analogy, consider modes of transport: freight is commonly shipped by air, by road, by train and by sea; in Zambia, very little moves by rail, nothing is moved by sea (can't think why...) and air-freight is... limited; we rely only on roads to keep things moving, which is fine up until a truck turns over coming over Danger Hill on the Great North and then there's no fuel getting into Lusaka or the Copperbelt for three days. Diversity = handy in a crisis. 

**Agriculture, charcoal and timber (in roughly that order) strip away the woodlands at an astonishing rate, and annual burning*** depletes the leaf-litter these insects spend their fomative years running around in, and prevents regeneration of tree populations by killing saplings, gradually creating more arid, grassland-savannahs, which just aren't as appealing to the adults. 

***In different parts of the country, the annual burning has different reasons: to encourage fresh grass to grow for livestock (especially Southern Province) or game (especially Muchinga); to make edible rats easier to see and catch (especially Eastern Province); to control ticks (National parks where the idea that the ticks are a vital and natural part of maintaining antelope diversity and predator populations has apparently taken an indefinite leave of absence), to stop other people setting fires (most large landowners' land), and to kill snakes (our neighbours). Some of these do have a good logical basis, but with Zambia's current population density, all are ill-advised. 

****That may seem cruel, because our imaginary population is human, but for most animal populations, one in a hundred being squished by a tree each year would be greatly preferable to the proportion that get eaten, squashed, diseased, shot, snared or run over by automobiles in any given year.