Monkey slugs and their cousins

I’m not a natural Lepidopterist – over recent years I’ve come to appreciate some of the less aesthetically appealling taxa and their fascinating ecology, so find beautiful butterflies a bit too ostentatiously pretty for my tastes! Moths, on the other hand, I find rather good fun – often (though by no means always) the adults are dull shades of greyish brown (though the wing patterns can often be wonderful), while the caterpillars can be bizarre to the point of otherworldly.

Hairy, spiky, multicoloured, mimicking something else or perhaps just resembling a fantastical piece of conceptual artwork, moth caterpillars can provide endless variety for a globetrotting ecologist.

One particularly memorable encounter in recent years for me has been with the caterpillar of a Caribbean species of cup moth (Lepidoptera: Limacodidae), probably a Phobetron species. We came across it in Trinidad and its appearance was so utterly weird it took me a minute to figure out what I was actually looking at. It was brown and hairy, with six to eight false “legs” and some whorls of hair that almost looked like suckers, and was crawling slowly across a small tree. I decided it would be inadvisable to touch it (which, as it turned out, was probably a good decision on my part, as various sources claim their spines can be irritant/toxic 1).

(Clicking links to a video of the creature walking down a tree)

I assume it’s trying at least half-heartedly for tarantula mimicry – if I was a hungry bird I’d definitely think twice.

Other closely related species can be even odder, with up to nine pairs of legs.

Their ecology is actually nothing particular special: they munch on various ornamental and horticultural plants, especially small trees. Although the coolest seem to come from the Americas, the family is also present in Asia, where one species is a pest of coconut trees as well as coffee, cocoa and oil palm2. Although there was once a bit of an outbreak of them3 in Panama following a rather severe drought, which makes for some pretty interesting mental images.

The diversity of Limacodidae caterpillars is pretty mind-blowing – lurid colours, hairy spines at strange angles. I suppose they remind me of what happens when a toddler gets to play in a particularly well-appointed dressing-up box!

Really, who needs sci-fi when you have Limacodidae?

With a caterpillar like that, what must the adult look like? Well, as is frequently the case with moths, this most wondrous caterpillar pupates into medium-sized, hairy but by comparison relatively uncharismatic adult moth. It has been suggested that the hag moth (Phobetron pithecium) is a bee-mimic, which I suppose is possible, though it’s perhaps not the most convincing I’ve ever seen!

Virginia Tech/Virginia State have produced a nice little factsheet on the North American species.

1Murphy, S. M., Leahy, S. M., Williams, L. S., & Lill, J. T. (2010). Stinging spines protect slug caterpillars (Limacodidae) from multiple generalist predators. Behavioral Ecology, 21(1), 153-160.
2Chenon, R. (1982). Latoia (Parasa) lepida (Cramer) Lepidoptera Limacodidae, a coconut pest in Indonesia. Oléagineux, 37(4), 177-183.
3Van Bael, S. A., Aiello, A., Valderrama, A., Medianero, E., Samaniego, M., & Wright, S. J. (2004). General herbivore outbreak following an El Nino-related drought in a lowland Panamanian forest. Journal of Tropical Ecology, 20(06), 625-633.


Adventures in the Caribbean: cocoa and beyond

This blog entry is brought to you, somewhat belatedly, from the lovely island of Trinidad in the Caribbean.

Trinidad and Tobago, while having a big strength in industry, engineering and particularly oil and gas, is mindblowingly biodiverse when you get out of the cities and into the rural areas. The cocoa agroforestry systems are particularly lovely, with new wonders almost around every corner!

Longhorn Orthop4

And it’s cocoa that’s brought me here. It’s an amazing tree, with flowers that come straight out of the trunk, and eventually develop (if pollinated) into vividly coloured pods about eight inches long. Like a lot of crops, it’s dependent on insect pollination – but while we’ve got a reasonable grasp of the pollination systems of crops like strawberry and oilseed rape in Europe and North America, with cocoa there are still big questions that we can only begin to answer with existing knowledge.


Starting with “What pollinates cocoa?”

Accepted wisdom is that cocoa is pollinated by 2mm long Ceratopogonid midges, particularly in the genus Forcipomyia1 – and, indeed, they seem to be the most effective insects for the job on a per-visit basis – lots of evidence suggests that they interact with flowers in the perfect way to pick up and deposit pollen, and that often one midge visit may be suffient to get a cocoa pod 9-odd months later2. However, they’re also relatively infrequent on a lot of cocoa fields, which raises the question of whether there’s really enough of them to account for the number of pods observed. How important are other small flies like Chironomids or Cecidomyiids? Do ants and thrips play a role, particularly in self-compatible cultivars of cocoa where pollen from another tree isn’t necessary for fruit-set? We don’t know nearly as much as we’d like to about the answers to these questions.

Similarly, how the midges find the flower is a bit of an unknown: do they see it, and if so…what are they looking for? Do they smell it – and if so, what are the important chemicals, and how much do they vary? What do they get from cocoa flowers that other flowers don’t (or do they?) provide?

And it seems that the cocoa needs them more than they need the cocoa. Everywhere cocoa has been planted in the world, be it Trinidad, Jamaica, Mexico, Hawaii, Ghana, Indonesia, Australia…, a species of Forcipomyia has shown up to pollinate it3. So clearly they were doing just fine long before the cocoa arrived, but once the cocoa is there they seem to derive some sort of benefit from it.

So…cocoa midges. While getting people interested in anything to do with chocolate is relatively easy, the midges themselves are somewhat less charismatic than other pollinators such as bees, hummingbirds or butterflies. Small, hairy, and closely related to various biting species – oh, and their larval stage is a 2mm long hairy maggoty thing that lives in rotting vegetation such as cocoa pods, rotting banana stem and leaf litter4.

Actually, understanding the larva is pretty important – while it’s the adults we need, we won’t get any if the larvae aren’t happy. That’s what we’ve ended up primarily focusing on this year in my current project out here. CocoaPOP (Cocoa Pollination for Optimised Production, or, formally, Optimizing Cocoa Production For Increased Yield and Income Generation) is a project co-funded by the EU via the ACP group of states, lead by the University of Trinidad and Tobago with partners from Trinidad, Jamaica and the UK. We’re looking at what’s going on with cocoa pollinators in the Caribbean – how healthy are the populations, what species are present, is the management supporting them, and how can we help? We’ve spent the last couple of years doing some fairly intensive insect sampling on 6 sites across 3 islands, to get an idea of what the pollinators do over the course of a year. We’re learning quite a lot and looking forward to publishing papers soon.

Now we’re on to the next phase – trying interventions to see how they affect pollinator numbers and eventual cocoa yield, and trying to understand the midges better. There’s evidence that this should work5, so fingers crossed! Rearing the little creatures in the lab is keeping us challenged, but we’re giving it our best shot! So I’ve spent the last couple of weeks busy in the lab and the field, helping to get the new experiments rolling and seeing what can be done to give us live midges in the lab to study.

I also had the opportunity to attend the first International Fine Cocoa Innovation Centre conference on the Ortinola Estate (formerly a cocoa estate owned by the Cadbury family, apparently). It was a great opportunity to learn about all stages of cocoa, from the genetics underpinning the important traits, through agronomy and then flavour profiles, marketing, small businesses and cooperatives. While the Caribbean is only producing a small amount of cocoa at the moment on a global scale, I think there is some real enthusiasm for increasing the region’s importance as a cocoa producer. I met some fantastic people from all sorts of areas of cocoa: academia, industry, SMEs and cooperatives. There was a pollination meeting/workshop afterwards too, which was an amazing opportunity to talk with lots of equally enthusiastic people about the next few big questions in cocoa production and discuss directions in future research.

1Billes, D.J. (1941) Pollination of Theobroma cacao L. in Trinidad, B.W.I. Tropical Agriculture (Trinidad), 18(8):151-156; . Posnette, A.F. (1944) Pollination of cacao in Trinidad. Tropical Agriculture (Trinidad), 21(6):115-118.
2Falque, M., Vincent, A., Vaissiere, B.E. & Eskes, A.B. (1995) Effect of pollination intensity on fruit and seed set in cacao (Theobroma cacao L.). Sexual Plant Reproduction, 8(6):354-360.
3Winder, J.A., & Silva, P. (1972). Cacao pollination: Microdiptera of cacao plantations and some of their breeding places. Bulletin of Entomological Research, 61(04):651-655.
4Besemer, H.A. & Soria, S. de J. (1978) Laboratory rearing of Forcipomyia spp. midges (Diptera, Ceratopogonidae): 1. Adult feeding, larval feeding and copulation trials; a revision of Saunders method of rearing. Revista Theobroma (Brazil), 8(2):43-59; Winder, J.A. & Silva, P. (1972) Cacao pollination: Microdiptera of cacao plantations and some of their breeding places. Bulletin of Entomological Research, 61(4):651-655.
5Groeneveld, J.H., Tscharntke, T., Moser, G., & Clough, Y. (2010) Experimental evidence for stronger cacao yield limitation by pollination than by plant resources. Perspectives in Plant Ecology, Evolution and Systematics, 12(3):183-191; Adjaloo, M., Banful, B.K.B., & Oduro, W. (2013) Evaluation of breeding substrates for cocoa pollinator, Forcipomyia spp. and subsequent implications for yield in a tropical cocoa production system. American Journal of Plant Sciences. 4(2):204-211.