Should we help maggots and caterpillars?

0:00This BBC podcast is supported by ads outside the UK. This is summer at its peak. Whole Foods Market Summer Fruit Fest is your invitation to eat the season. Fresh, organic, and bursting with flavor. Start your day with peaches and organic blueberries and yogurt. Build a grazing board with fresh fruit, prosciutto, and artisanal cheese. Then fire up the grill with no antibiotics ever proteins and fresh produce. Savor the season. Shop Summer Fruit Fest at Whole Foods Market. Ask yourself, what are your best people spending their time on right now? Expense reports, receipt chasing, month-end close that takes weeks.

0:40You become what you spend on, and that's not what you're building toward. Brex is the intelligent finance platform that eliminates that work before it starts. AI agents that handle the manual stuff automatically, so your team can spend their time on what actually compounds. It's time to get Brex AF. Learn more at brex.com slash AF. Because you're a good presenter, I've got your present. Okay. Open it up. Oh, I should open it. I might be able to open it. We've got a bit of paper. We can tip it. Presumably we can tip it out. All right. It looks like tiny leaves. What's that there? They're crawling everywhere.

1:23What it looks like is some sort of mini alligator ant hybrid. If you imagine some sort of transforming robot that you'd see in a movie, it would be like that, but a few millimetres in length. Definitely nothing like a ladybird, even though that's what's written on the jar that they come in. You know we have to count every single one we find, because if we leave even one here... Actually, that's a really good point. They are crawling off in different directions. Yeah, we should probably get them. There's one here. Oh, we lost one. It's making a break for freedom, and we cannot have that. I'm Alex Lathbridge.

1:59Welcome to the chaos of crowd science from the BBC World Service as we inspect producer Marnie's latest acquisition. How many are there? 250. I couldn't buy fewer than 200. Oh, there's another one on my hat. Right. Okay. Oh, there's more on the back. Yep, I think this was a terrible idea. But, you know, a great idea for the aphid problem that is currently attacking my producer's tomatoes. And also nice to meet some of the subjects of this week's crowd science face-to-face. Or antenna to antenna. Oh, they are everywhere. They're actually everywhere. I'm really sorry. Oh.

2:50Sorry. The reason why producer Marnie and I are wrestling 250 ladybird larvae back into a box before they can escape to neighbouring BBC studios is because of a very insect-y question from this week's listener Ruth from Scotland. So we're heading to the Royal Botanic Gardens Edinburgh to meet her once these ladybirds are dealt with. My name's Ruth. So in my garden over the summer, I've been really enjoying seeing all the bees and the butterflies. but the one that I really like are the hoverflies because their sound is so unique to them that even with my eyes shut I can tell when it's a hoverfly that's flying there and especially when they're on my calendula they make a specific pitch of sound what's the sound?

3:38it's a certain pitch hit me beep exactly like that well maybe not

3:46so yeah it got me thinking about the other pollinators really because you've got the big celebrities of butterflies and bees but there are so many other ones you know the ladybirds and the ants and the moths and the hoverflies that do so much as well so then I went and thought more about my hoverflies where do they lay their eggs what do their larvae look like, what do their larvae eat and then I thought we're looking at the butterflies because they're pretty and they're colorful but how often do we plant for the caterpillars and there is an irony if you think about it you plant your wildflower meadow for the butterflies and then right next to it you put netting over all your brassicas you know your cabbages and your broccoli to stop them laying their eggs so it's like come in, come in for all this feast but don't lay your eggs and I don't want your caterpillars in my garden Crowd science listener Ruth is right.

4:50Many of us might love to see a butterfly, but those butterflies in the younger phase of their life cycle live as caterpillars, often seen as garden pests, which gardeners who value their cabbages downright dislike. Well, at the core of Ruth's curious conundrum is a single question. How can we learn to love the insects in the world around us, not just the bees and popular pollinators that get lots of attention. Ruth, you have lots of questions, many different questions. I thought actually the best thing to do is to bring you to Royal Botanic Gardens here in Edinburgh and put you in front of some experts who can answer that.

5:34So before we get into that, could I please get you to introduce yourselves. I'm Caitlin Johnstone. I'm an ecosystem and nature-based solution scientist here at the Botanics. I'm Nicholas Balfour and I'm a pollinator ecologist here at the Botanic Gardens. So if I understand this correctly, Ruth, more or less you want to know why do bees and butterfly, why do they get all the limelight? Well bees and butterflies I guess are the pandas of the insect world i mean they're big and beautiful and everyone seems to like them and butterflies of course change and because of their metamorphic lifestyles and i mean also that was great because they are umbrella species just like pandas so all the conservation actions sorry that we can undertake for the bees and butterflies can also have a an effect right across the insect world which is great what are your thoughts they do deserve the attention but so do all the other insects and a big part of why we don't is that you see the bees and the butterflies you as a human when you're out and about they're flying right about at eye line they're bee bopping around when it's nice and sunny and hanging out with the flowers that the humans are visiting but there's so much more to the ecosystem that we just don't sea.

6:58So things that are crawling at ground level or have some incredible camouflage and they're hiding underneath of leaves or blending in with the sticks or they come out at night. You know, caterpillars are out there doing a lot of their foraging at night when the sun goes down. Moths, which can be just as beautiful and have those fluffy bodies and are also pollinators. They're mostly flying around at night. And so as humans, we don't see them. So it's a little bit out of sight and a mind but just as important okay okay okay but apart from bees and butterflies what other lesser known you know pollinators that we should really care about i guess flies often don't get the respect reserve i mean they're much more species of flies for example than our butterflies but particularly for crops and for a lot of the plants so about 80 or 90 percent of the plants in the world rely on insects to some degree or animals for pollination to complete their life cycle and about a third of all the crops that we eat as well.

8:01And many more things than just the bees and the butterflies are pollinators so when we talk about pollination we're saying we're getting the pollen from one flower to another flower and we're looking at plant reproduction. When producer Marnie and I accidentally let those 250 ladybird larvae loose in the studio, they look nothing like the ladybirds we're used to seeing. Like many insects, they go through a process known as metamorphosis. So, beforehand, they look like teeny tiny black alligator-like creatures which, of course, grow and change into the small, round, red and dotted beetles that we're used to.

8:44So that's ladybirds. And if you want to have a garden full of butterflies, you need to accommodate their caterpillars.

8:54Like Nick and Caitlin mentioned, flies are wonderful but lesser known pollinators. And listener Ruth is interested in how we can learn to love these useful insects. So we decided to go hunting through the gardens to see if we could find one of Ruth's favourite species, the hoverfly. Maybe finding these pollinators and seeing them hard at work will make me love them more. So we've got a hoverfly here, forging on. You want me to tell you how you can differentiate a hoverfly for a bee, for example? So hoverflies, only two wings. And you'll notice they're not hairy like bees as well, which is a bit of a giveaway.

9:38and of course given the name you won't be surprised to know they hover. Do they nest, like are they social lovers? Like where do they all live? No, they're pretty much... Are they solitary? Solitary, yeah. Sociality doesn't exist so that would be the difference. And how would you tell the difference between a male and a female hoverfly? That's a good question actually. If you look at their eyes, if their eyes meet in the centre then they are males and if they don't, then there's a bit of a gap female. Cool. So that's a nice easy start. Now that's the take on this. It's more obvious in some species than others, but yeah, if you have a look.

10:16Yeah, they look, they wouldn't say the most attractive larvae. Fly larvae tend to be... A bit maggoty. A bit maggoty, absolutely. So probably not the most charismatic of larvae, I'm afraid. I don't know, they can be a bit cute. Well, if you like a maggot, then yeah, sure. I don't know where hoverflies lay their eggs or what their larvae like. Hopperfly is a very diverse group in terms of their lifestyles when they're in the larval stage. So some are predators. There's even a biological control that they're using some crops. For example, tomatoes and strawberries. You can buy hopperfly larvae of some species and they will go ahead and eat all the aphids and such.

10:58In the larval stage? In the larval stage, yeah. And some are decomposers. There's one species that even uses reed straws to breathe through, which I believe under water, which is quite unbelievable. It's snorkeling. And they are pollinators as well. They are, absolutely. All the adults will be feeding on flowers. So these lesser-loved hoverflies play a huge role in the world around us, even when they're still teeny tiny larvae. When adult hoverflies are buzzing around and feeding on flowers, they're helping the ecosystem by pollinating those plants. And far away from Scotland, in the south of Spain, hoverflies are working really, really hard.

11:42So my name is Marc Bessolivera. I'm French, but started the company in Spain. Marc's company, Polyfly, is rearing hoverflies, with the ultimate aim of helping farmers make more food. What we do is mass rear certain species of hoverflies. So we focused on only two of these 6 ,000 species, basically in excess of a billion hoverflies per year. And what we do in our company is we breed them in a controlled environment, in a controlled facility, where the whole production cycle can be completed. In their facility in Almeria, that circle of life for hoverflies starts with adults who are encouraged to quite literally breed like flies.

12:29So we breed them. We basically have them in a special room under special conditions. So we breed, mate, produce eggs. And then we transfer those eggs into separate larvae production area. And the larvae is basically, you know, that crawling stage of the insect where it feeds and it's between the egg and the pupae. The pupae, once the larvae is done feeding, it's when the metamorphosis takes place. And that's a stage of the development of the insect when the cells inside the pupae reorganize and basically reshape into a new organism. That is the adult that will come out and emerge from the pupae.

13:10And the pupae is our end product. Part of the pupae is selected to renew the breeders, the colonies, and repeat the cycle. But the excess of pupae that we have is basically our end product that is packaged into boxes for collination purposes. Those pupae are packaged up and sent across the world to be unboxed and work in farms and greenhouses. But how do you convince growers to give these hoverflies a chance when bees and other pollinators will do it for free? Yeah, absolutely. We do case studies. Pollination ultimately can be quantified. So we are scientists and engineers in our DNA in the company, and we want to be able to show scientifically over the course of several seasons that hoverflies can increase yields by an actual accurate amount.

14:02We've done that with several growers over the course of several seasons because pollination is a complex equation, right? The yield of a crop is not only the product of pollination, it's also the product of weather conditions, pests, stress, nutrients availability. So there's a few variables that come into play. So we need time to validate that. But we've done that. And in some cases, we've over doubled the yield of avocado produced on avocado farms. Just pausing to point out how impressive that is. Now imagine you're a farmer. You're going to be quite interested in doubling the amount of the crop that you're taking to market.

14:40Just because some hoverflies have hatched on your plants and got to work fertilizing more of the flowers and turning them into fruit. And that's very significant because if you think about it, we are talking a lot nowadays producing more with less. I think pollination is a well-understudied lever to achieve that. If we pollinate better crops, we can reduce the land area necessary to produce a given amount of that crop. So listener Ruth thinks that there are unsung insects out there. And so far, we've heard that although bees and butterflies are important for pollinating, there are many other less flashy insects, maybe some camouflaged, maybe others working at night time that are needed by about 85 % of plants around the world to complete their life cycle.

15:36And from talking to Mark at the company Polyfly, I have a newfound respect for hoverflies and their work on avocado farms. This is summer at its peak. Whole Foods Market's Summer Fruit Fest is your invitation to eat the season. Fresh, organic, and bursting with flavor. Start your day with peaches and organic blueberries and yogurt. Build a grazing board with fresh fruit, prosciutto, and artisanal cheese. Then fire up the grill with no antibiotics ever proteins and fresh produce. Savor the season. Shop Summer Fruit Fest at Whole Foods Market. Ask yourself, what are your best people spending their time on right now?

16:18Expense reports? Receipt chasing? Month-end close that takes weeks? You become what you spend on, and that's not what you're building toward. Brex is the intelligent finance platform that eliminates that work before it starts. AI agents that handle the manual stuff automatically, so your team can spend their time on what actually compounds. It's time to get Brex AF. Learn more at brex.com slash AF.

16:48you're listening to crowd science from the bbc world service i'm alex lathbridge and this week we're inspired by listener ruth to look at the useful insects that we don't really notice or appreciate doubling the yield of avocados is pretty impressive but i think i can convince even more of you by sharing the story of chocolate. We're moving from hoverflies to an even less loved insect, the midge. They are small, rather bitey insects. Think a mini mosquito. But what they lack in size, they make up for in quantity. They hang around in clouds, ruining people's holidays. but I said there were positives to this.

17:36My name is Dr. Tanya Lander and I'm a lecturer in biology at Christchurch College at the University of Oxford. I'm just going to put right now, I've got, got and hear me, my producer Marnie has come to me in the studio with a little box of chocolates. I'm just going to put one in my mouth while I ask this complete random question. Wonderful. Completely at random. Where does cocoa come from? Right. So the cocoa that we eat is made from the roasted and ground seeds of the cocoa pods on a cocoa tree. And cocoa trees are native to South America, but now they are grown throughout the tropics. Some of the biggest producers are in West Africa and Indonesia.

18:21So which insects are responsible for pollinating cocoa plants? That's a really good question. So there is a group of midges that are thought to be the most important pollinators, particularly in the native range in Latin America, and they are the Ceratopognidae. but there's quite a bit of evidence that many other insects visit these flowers and the flowers themselves are really special they're very beautiful but they're also extremely tiny and they grow not only out on the branches and the twigs as you sort of imagine trees or flowers on a tree but they also grow right down the trunk of the tree so the tree is kind of decorated with this frost of tiny white flowers.

19:06And so it's tiny things that visit the flowers, which is part of why we don't know that much about it. The flowers themselves are extremely small and they only last for a day. They bloom and then fall off. And the insects that visit them, the midges, are extremely small. And then the other things that visit the flowers are things like ants. And so although we can put a camera trap, for example, on a flower and watch who comes to visit, determining which ones are actually the most effective pollinators is quite an effort. So what Tonya is saying is that even though chocolate is a multi-billion dollar industry, we aren't even sure which insects are doing the pollinating of the tiny flowers that then turn into cocoapods, which are turned into chocolate.

19:57It's probably midges though. And you could argue that it doesn't matter as long as the trees are happily producing their crop. But they aren't happy. Cocoa trees don't like high temperatures, which makes them vulnerable to a warming climate. So a team of scientists, including Tonya, set about working out which factors are limiting how many cocoapods a tree can produce. I am Dr. Champon Atabwaten. I'm originally from the eastern part of ghana and i live in accra right now i am a plant physiologist and i work at the intersection of physiology and ecology okay so in this program what we're really interested in is is pollinating insects and i know that you've done a bit of work looking at the pollination of cocoa plants and I'm wondering could you tell me a little bit about the the research you've done and the field work that was involved?

21:01The field work occurred in Takwa Breman which is in the western part of Ghana. It's predominantly rainforest it's very rich in terms of agriculture especially cocoa production that is where I did my cocoa pollination work. I worked on eight plantations across a cluster of village towns. And the pollination required, of course, a teamwork with folks that I recruited from the villages and I trained to help me with the hand pollination. You heard that right. Hand pollination. Achampong had a hypothesis to test. Basically, we wanted to attest to the hypothesis that will help us to understand how much pollination contributes to cocoa yields.

21:50And so the work really involved us establishing a control, which was natural pollination where there is no interference. And then we had some other controlled systems where we varied pollination rate from 0 % to 40 % up to 100%. So while the insects were left to pollinate most trees as normal, on certain patches of the plantation, Achampong and his team had to hand pollinate different proportions of tiny cocoa flowers, which is exactly as tricky as it sounds. Cocoa flowers are quite tiny. It's smaller than your fingernail. And because of that, collecting pollen is kind of a mammoth of a work. so what we do is we go early in the morning and then move from tree to tree and try to get pollen and because they are so tiny you have to collect as much pollen that you can and then once you fast sufficient you will now then move to a different tree and try to pollinate you just scoop take a scoop of it a tiny little scoop and then patch it to the tip of the stigma and so from all this i imagine it's a lot easier for insects to do exactly they are extremely efficient and and i think that if not the for the sake of an experiment i don't think anybody would like to do that kind of job so after all your laborious field work does chocolate taste different for you now.

23:28Oh goodness my love for chocolates have never been the same. Yeah simply put. Their work was published in a paper earlier this year which suggests that hand pollinating increased yields by 20 percent and what that means is that these cocoa trees are currently being under pollinated by the available insects because there aren't enough insects. Yeah so in the areas where we were working we found fewer flowers were being fertilized than the trees were physiologically able to support so it could have produced more fruit than it was producing with the natural amount of pollination and so what that means from a farmer's point of view is that they're not producing as much cocoa per unit area of their plantation as they could.

24:19And that's an economic shortfall for them. Let's face it, no one really likes midges. But it's almost certainly them doing the important work pollinating one of the world's favourite crops. That's the best case I've heard yet for an unloved insect like the midge. More midges, more chocolate. But that brings us back to listener Ruth's question. If we only look after the pretty insects that like pretty flowers, what happens to those insects when they're in the earliest stage of their lives as grubs or caterpillars? How do we make sure that they're looked after as well? Back in Scotland, listener Ruth, entomologist Nick and plant ecologist Caitlin are still on the hunt for some elusive insect larvae.

25:07It's a very good thing in a garden to see holes in your leaves. You want that to happen. You want to see that your plant is actually part of the ecosystem. Found a caterpillar. Oh, well done. We found a caterpillar. Mid-interview, producer Marnie has found a caterpillar. What am I seeing here? What species that is? I don't know the species, but it looks like the way it's maybe might be a geometric, so that's probably a type of moth caterpillar. That's a very big family. We've got over a couple of thousand species of moths in the UK, so don't expect me to narrow it down, I'm afraid. I mean, it's grey and sort of squidgy looking.

25:44I'd be liking the warmth of her hands as well, I would say. So would this guy be looking to pupate, or is he looking for food? Well, it depends. Some moths will overwinter as eggs, some in the larval stage like this one. Some will even overwinter as adults as well. Ruth is very happy with the caterpillar in her hand, and she'll obviously want a lot more in her garden. So what should she do to keep caterpillars and other lesser-loved creatures happy? Well, planting native wildflowers is probably the best thing she can do. Planting native plants, native trees. Even if you've got a small garden, you don't need to have a pond.

26:21You can even have a plate with some water and a few stones on there. Caitlin, Nick, if there's one thing that you could tell our crowd science listeners across the world about the lesser loved insects of a garden and what would it be what would you want to tell people well I'm going to say we're standing here in front of this chestnut tree that's fallen down and I'm looking at these nettles here and actually there's four really beautiful butterfly species which eat nettles when they're in the larval stage, we've got the peacocks beautiful butterfly, we've got the comma, we've got the small tortoiseshell and I think the Red Admiral as well so you know tolerating weeds even nettles which you know most people would be wanting to get rid of in a heartbeat but without these nettles we aren't going to see these beautiful adult butterflies that we all enjoy seeing flying around so that would be my take home and mine would be that nature is alive so the soil is alive even the dead litter the dead wood that we think of as dead it is alive with insects, with larval stages, with things overwintering or dormant or in cocoons that you wouldn't immediately think of that are just it's it's bursting with life.

27:41And so if we change our mindset to think of our garden as an ecosystem and ourselves as part of it, we're automatically going to start making all of these small changes.

27:56so ruth you asked how do we learn to love the less loved insects the answer might come down to in part better pr i hope that we've done our bit to showcase the cocoa in west africa and avocados in the south of spain or the countless other crops and flowers that we see in the world around us that owe their existence to hoverflies and other less loved insects. And if you're someone who loves to see the butterflies, ladybirds and other beautiful insects in your garden, remember you've got to embrace them at every stage of their life cycle rather than treating the larvae and caterpillars as unsightly pests.

28:39Now before you fly away to plant some wildflowers, throw away your lawnmower and lock away your weed killer, here's Ruth with the credits. That's it for this edition of CrowdScience from the BBC World Service. The question came from me, Ruth, in Edinburgh. The show was presented by Alex Lathbridge and produced by Marnie Chesterton. If you have a question for the team, please send it to crowdscience at bbc.co.uk. Thank you for listening. Bye.

29:19The United States is about to mark its 250th anniversary. And so on the Global Story podcast from the BBC, we're telling surprising tales of American influence on the world stage and in ordinary people's lives all across the globe. We have this ability to export our story and a lot of people have bought it. I feel like the American dream is alive but not well. From the BBC, it's the United States at 2.50. Listen on bbc.com or wherever you get your podcasts.