Sarah Arnold

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A flashing light may not be that flashy: A systematic review on critical fusion frequencies Background Light pollution could represent one of the main drivers behind the current biodiversity erosion. While the effects of many light components on biodiversity have already been studied, the in...

journals.plos.org/plosone/arti... Good that this is being studied in the context of light pollution too.

The flicker fusion frequencies of six laboratory insects, and the response of the compound eye to mains fluorescent ‘ripple’ ABSTRACT. The ERG response of the compound eye to single, brief, light pulses, to sustained stimulation for 2 s, and the dark adapted flicker-fusion frequency (FFF) under stroboscopic light was meas...

OK, yeah, so obviously I had to go and look this up and yes, there is loads of variability depending on taxonomy, eye structure and diurnal v nocturnal lifestyle. resjournals.onlinelibrary.wiley.com/doi/abs/10.1...

Been a while since I looked into it in detail (but need to revisit it), but I think some species can detect higher flicker frequencies than others, yes.

...seems reasonable that some more sensitive humans would similarly be thrown if they could detect the mains flicker or any other flickers that are coming off them.

Really interesting - when doing behaviour work with insects, you have to consider the flicker-fusion frequency of the lights and whether that could compromise your experiment (and if necessary fit some extra kit to increase it beyond what an insect would detect)...

It's a deal!

Sorry, I'm one of those weirdo ones who gets dysregulated by rooms that aren't bright enough...! Give me all your all Big Light. (As long as the colour temperature isn't too cold.)

A bright yellow shaggy-petalled dandelion flower on which a medium sized golden-orange bee is sitting. She has impressive flowing orange hairs on her hind legs, a more tawny thorax and her abdomen has tawny-interspersed-with-more-blond hairs on. She looks dopey but tidy and fresh, and she is a real live bee on a flower in February!

I know you folks in eastern USA are still wrapped in your woollies (stay safe!), but here in the UK it is getting warmer and brighter and the first solitary bees are out! Andrena bicolor female today! #SolitaryBee #Entomology #FirstBeesOfSpring #Bee #Pollinator

A microscope image of a small but not tiny ladybird (3mm), black all over on the back, but covered in short pale hairs. And because it's a bit hairy, it's snagged a few bits of light detritus as well - fibres, bits of crud, that sort of thing. The centre of its elytra are less hairy and lightly punctured.

The same ladybird under a microscope, but zoomed out. This shows the slight shininess at the top of the elytra and the fine pale hairs over most of it. The shape is oval but not as elongate as some of the smaller micro-ladybirds.

The same ladybird (3mm long, otherwise black, under a microscope) rolled on to its back, showing that the abdominal sternites are bright orange-red.

Fun surprise this week - this delightful ladybird dropped out of a bush at work while beating some foliage. Having not met one before, I assumed it was a massive Scymnus, but no, it's Rhyzobius forestieri, an introduced species from Australia, just hanging out. Rather exciting! #Entomology #Ladybird

They're adorable! I did see some on a cabruca farm in Bahia. And being used to pollinate strawberries in Atibaia. Stingless bees have so much potential as part of agri-systems as they're so diverse - just need to understand their needs and ecology more.

I do really want to explore whether the smallest species of stingless bee can play a role in cocoa pollination - Jatai I think might be on the limit of being small enough. When I was in Ghana there were some even smaller ones nesting in a doorframe in the village that I think might work if reared!

Yeah - it's been nice to see solid yields coming in from in-project farms in an otherwise very challenging production period!

A cocoa tree in dappled light, with its trunk absolutely covered in pale creamy-white flowers, each about 1cm across and coming straight out of the trunk, not on twigs or anything.

We're also studying more about pollinators' use of breeding substrates on farms so we can improve recommendations to boost pollinator numbers on-farm. Project funded by the Joint Cocoa Research Fund & Mondelez, & includes scientists from KNUST(Ghana) & Niab, Durham University & NRI (UK). [21/21]

We are now trying to understand how well trees can keep up the high yielding if you manually pollinate same trees year-on-year. Does it exhaust them? Early data implies it doesn't, but we don't have all the data we want yet. (Erratic climate in cocoa-producing countries affects research too!) [20/]

The trunk of a cocoa tree that is very heavily covered in developing pods, close to maturity, but not quite there (pods green and have some growing to do). Credit: Michael Adjaloo

But does manual cocoa pollination work? Ohhhh yes! We've seen big boosts in pod number/size from trees getting manual pollination, even on farms that are low-input and the trees are old/not in the best condition. Economics depends on labour-cost by country & market prices. [19/]

Manual cocoa pollination requires a steady hand, good dexterity and good close vision - so it may be best to consult a specialist if you wanted to try but are not confident. It's not for everyone, and some countries do it more than others. [18/]

This is fiddly as cocoa flowers are small and delicate, but involves taking the male reproductive parts (anthers) and touching the to the female reproductive parts (stigma) of a flower from a different tree (and different variety - cocoa is quite particular about its pollen compatibility). [17/]

What else can cocoa farmers do?

One option that, to an entomology nerd like me, feels a bit "cringe" initially, is to supplement natural cocoa pollination with hand (manual) pollination... [16/]

A Brazilian cabruca farm, with the cocoa trees almost an afterthought amongst towering shade trees and other plants everywhere. It is very lush and verdant, with many plant species present.

Sciaridae: Damp soil & rotting vegetable matter again!

Parasitoid wasps: Need something to parasitise e.g. aphids, caterpillars, leaf-mining fly larvae, mealybugs. Also need nectar sources. So plant diversity probably good! Need research into which species use cocoa flowers in each country. [15/]

A rather odd looking midge under a microscope, about 3mm long perhaps, with very long gangly legs, quite long antennae, and wings with only 2 main veins really. The fly is pale, almost transparent in places, with prominent halteres and a head that is dominated by big dark compound eyes.

Cecidomyiidae: These have a range of lifestyles, but many are gall-formers that grow inside plant material. So most likely...plant diversity will be good, as will be moist soil for some life cycles. [14/]

A clearing in a cocoa farm, with banana trees around the edge and a shade tree in the middle. At the base of the shade tree is a big pile of fresh, yellow cocoa pods. Around that is a ring of old, rotten, blackened cocoa pods.

What do cocoa pollinators like?

Ceratopogonidae: Moisture is key: the larvae mostly develop in rotting slimy plant material like cocoa pods and banana pseudostem, also moss clumps, leaf litter, etc. If it dries out, they are not interested. Drought is not their friend. [13/]

A tiny parasitoid wasp under a microscope - probably barely over 1mm long in real life. But magnified, it has long, elbowed, clubbed antennae, and a cool abdomen that is yellow with dark brown stripes.

But this is just Ghana! Results from other countries with different systems may show, e.g. more parasitoid wasps as pollinators, even on cultivated cocoa. No reason all countries will be the same. [12/]

Aphids and ants end up inside cocoa flowers a lot! Do they play a role in pollination? The jury is still out - it's possible, but requires a few caveats for it to work. Hope this is more studied in coming years. [11/]

...but other midges (Cecidomyiidae, Sciaridae) and Drosophilid fruit flies, among other species, were also entering flowers and making regular contact with flower reproductive parts. [10/]

The team sampled pollinated (& control non-pollinated) flowers from Ghanaian cocoa farms & the Durham specialists extracted eDNA from the flower surfaces. The visitors to the plant reproductive parts included a whole range of small flies - Ceratopogonidae were a small % of visitors... [9/]

Some of our project work (Niab/Durham Uni/KNUST/NRI, funded by JRF/Mondelez/Swiss Foundation of the Cocoa and Chocolate Industry) also finds that the eDNA present inside cocoa flowers (left behind by visitors) reflects a varied community with Ceratopogonidae only a small part of the mix. [8/]

Camera-trapping of flowers by teams in China and Brazil suggests that a diverse variety of insects visit cocoa flowers and contact reproductive parts, including not just various small fly/midge groups (more than just Ceratopogonidae!) but also ants, aphids, etc.
www.biorxiv.org/content/bior... [7/]

However, new studies have shown that it's much more complicated.

Parasitoid wasps seem to be really important in wild cocoa. They're usually a bit smaller than "cocoa midges".

Chumacero de Schawe, C., Kessler, M., Hensen, I., & Tscharntke, T. (2018). Agroforestry Systems, 92(1), 117-125. [6/]

An image of a midge that is mostly dark brown, with more yellowy legs. It is pictured in a microscope-magnified image so the lighting is a bit odd. In real life it is about 2.5mm long. The wings have fine hairs along all the veins and around the edges.

They are present on cocoa farms. The larvae of some species develop nicely in cocoa pod husk as it starts to rot a little bit and get slimy.

They have fairly hairy bodies, and some studies have found that lots of cocoa pollen can stick to those hairs. So the potential is there. [5/]