Trapping the Spotted Fruit Fly

The Spotted Wing Fruit Fly, Drosphila suzukii, (known as ‘SWD’ for short) is a small but potentially devastating pest that attacks soft fruits. Here’s how to make a simple trap from a plastic bottle. You can then see if you have caught any fruit flies and send your results to an exciting citizen science project.

Making your Fly Trap

You will need:

  • A large empty clear plastic bottle (perhaps a fizzy drink bottle or squash bottle)
  • Apple cider vinegar (cheapest from a supermarket)
  • Washing-up liquid
  • String
  • Ruler
  • An auger, awl or large nail (2 mm to 3 mm diameter)
  • A magnifying glass OR a low power stereo microscope (OR a camera phone and some honey!)

What to do:

Start by watching this video by Chris Thomas of the Queckett Microscopical Club. It shows each step of making the fruit fly trap.

Step by step Instructions:

  1. This bit needs an adult to help. Carefully pierce 8 holes in the bottle more than half way up, using the augur or nail. Lie the bottle on a table or board. Hold it firmly at the bottom half and gently pierce with a sharp metal point or augur, through the upper side of the bottle towards the board. If the point slips, it should then go safely into the table or board and NOT into your hand. Make the holes 2-3 mm in diameter, to let in small flies. I used a sharp augur to pierce the plastic and then a wider diameter nail to enlarge the hole.
  2. Fill the upright bottle to ¼ to ⅓ with apple cider vinegar. The level must be below the holes!
  3. Add one or two drops of washing-up liquid.
  4. Screw lid back onto plastic bottle.
  5. Use the string to hang your baited trap from a tree/bush/holder at a suitable place.
  6. Leave the trap for one week.
  7. At the end of the week, seal up holes with sellotape.
  8. Swirl bottle gently and carefully pour the fly catch into a white / light coloured plastic dish. (OPTIONAL: strain the fly catch through an old metal tea sieve and then transfer the flies to clean water with a bit of vinegar in it to preserve them.)
  9. Record your results (see below).
  10. At the end of the experiment, wash and flush away the flies and liquid. Wash the plastic bottle thoroughly and recycle it. Don’t forget to wash your hands.

2021 Spotted Fruit Fly Survey

If you have caught some fruit flies, you could send your results to the 2021 Spotted Wing Fruit Fly Survey and help track the spread of this pest across the UK.

Drosophila suzukii on a ripe banana. Image credit: Flickr / Martin Cooper CC BY 2.0

The Spotted Wing Fruit Drosophila (SWD) is a pest in many parts of the world because it causes damage to soft fruits. It was first spotted in the UK in 2012 and this survey aims to find out how far it has spread. Counting and scoring the results from your trap will be really helpful and we will link your results with those from many other people. The more people who contribute, the more we can learn about the biology of this pest.

Fruit flies are small – only a few millimetres long – but can be identified by a couple of key features with a hand lens, low power microscope, or by using a mobile phone camera (see below). The male flies are easily identified by their characteristic wing spot. The females don’t have the wing spot but do have a vicious-looking saw-like egg laying organ (called an ovipositor) at their rear end.

You might like to use your fruit fly trap to catch Spotted Wing Drosophila over a week, count what you have caught and send the results to Chris Thomas of the Quekett Club at bulletin@quekett.org by the end of November.

The Club aims to collate all the results and publish them in the Quekett Journal, mentioning all participants who submit results.

Identification help

How to identify male and female Spotted Fruit Flies. Image credit: © Queckett Microscopical Club
  • Either use a magnifying glass or a low power microscope to magnify the catch. Don’t worry if you don’t have one – watch our video Turn Your Phone into a Microsope.
  • Fruit flies are very small, between 2 mm and 5 mm long. They are quite distinctive.
  • Use the pictures to help you identify the Spotted Winged Drosophila.
  • The male flies are obvious even to the naked eye – they are red-eyed fruit flies with a black spot at the end of the wing. Under magnification, they also have 2 spurs on their forelegs.
  • The female flies are best viewed under 10× to 30× magnification: they have no spots but their saw-like ovipositor (egg-laying organ) can be seen clearly. Once you have seen one, you will never be confused. They also have clear black and yellow bands on their abdomen.

Record your results and send them to the Quekett Club

You should include:

  • Name and address (or just your post code, if you don’t wish to be named as a participant)
  • Date when you emptied the fly trap
  • Total number of ALL insects/creatures in trap
  • Total number of ALL fruit flies
  • Number of male Spotted Wing Drosophila
  • Number of female Spotted Wing Drosophila
  • The Queckett club would love to see pictures of your catch, so please add them too
  • SEND YOUR RESULTS TO  Chris Thomas at bulletin@quekett.org by the end of November.

It’s really important to record and send in ALL results – even if you did not catch anything!

  • If you don’t catch anything, enter ‘Nothing’
  • If there are no Spotted Wing Drosophila, but you see other fruit flies, enter ‘Common Fruit Fly’
  • If you can’t decide if they are males or females, just tell us the total number of SWD

Make sure you send your survey results to Chris Thomas at the Quekett Club, but the team at Crunchy on the Outside would also like to see your fly traps and catches! Let us know how you got on by emailing us at hopelearning@oum.ox.ac.uk or using the Contact Us form.

Turn Your Phone into a Microscope

What if you need to look at something really small but you don’t have a microscope? You can can try taking a close-up picture with a smartphone or camera (use the ‘macro’ setting if it has one) and then magnify the image by zooming in on the picture using a PC or tablet screen.

Alternatively, we’re going to show you how to hack your phone to turn it into a microscope. You don’t need any technical skills or special equipment – just some honey!

Honey Lens Hack

You can buy magnifying lenses which are designed to sit over a phone camera lens, but our video shows you how to use a drop of honey as a temporary magnifying lens. You don’t need much, just these five things:

  • Scissors
  • Clear plastic packaging (e.g. plastic fruit carton)
  • Blu tak (or similar)
  • Teaspoon
  • Clear honey (if your honey has gone solid, the video shows you what to do to solve this)

You’ll probably need to experiment a bit with the size of honey drop you use exactly how far from the lens to position it to get the best image. With a little bit of practice you should be able to make a useful temporary magnifying lens.

We would love to hear how you get on, so please let us know using the Contact Us page, or by emailing us at hopelearning@oum.ox.ac.uk.

Fabulous Insect Photos

Wildlife photographer and insect enthusiast Kirk Mason shares his top tips for taking fabulous insect photos, whatever camera you have.

Well done to everyone that came to the Summer School photography workshop. I was blown away with your photographs, videos and knowledge of insects – well done!

Let’s recap on some handy hints to improve your photography.

1. Getting down to the eye level of insects.

One of the things that makes photographing insects and other invertebrates so awesome is that you start to see things in photographs that you would have missed with just your eyes. Getting down to the eye level of insects makes them look bigger, more impressive and can take your viewers to a perspective they wouldn’t have seen without you. If you compare these photographs, which do you prefer?

2. Empty space.

Leaving empty space in your photographs can make your subject really stand out. It leads the viewer’s eye to what you want them to focus on or show your subjects in their environment. You can use the rule of thirds to get a feel for how much empty space you should leave – ideally the subject should take one third of the space, and two thirds empty space. Though artistic rules are made to be broken, so the best thing to do is experiment and see what you like most! Check out the examples below to see what you prefer.

3. Background is everything!

Leaving empty space can look great, but if the background is messy or doesn’t look nice to you, it can take away focus from your subject. Most insects and other invertebrates are tiny, so moving around the insect by a few centimetres can really change the look of a background and the feel of a photograph. See below for examples of a bad background made better by moving a few inches, which do you think looks better?

4. Focus on the things that you find interesting about the subjects.

They say the eyes are the window to the soul, and whilst invertebrates do not show emotion through their eyes, they are often super interesting to look at! Typically, having the eyes in focus makes for great photographs, however invertebrates have lots of interesting features that are great to see up close! Wing patterns, antennae shapes and even feet are super diverse and make for great photographs – here are some examples of things I find interesting, do you?

5. Practice makes perfect!

Photography is like many things we do in life – the more we practise, the better we become! Luckily, going out finding insects and photographing them is great fun. This makes improving feel almost effortless and with thousands of insects to find in Britain, it’s hard to get bored! Wind and fast-moving insects make it hard to get good photographs every time, so the more you take, the higher chance you have of getting the shot you want. I still throw away way more photographs than I keep! I started my photography journey three years ago and have since had my photographs on BBC Springwatch, and in BBC Wildlife magazine and several newspapers. See below for my first photograph that I was happy with and compare it with what I take today. You all took fantastic photographs and if you keep doing it, by the time you are my age, you will have taken the world by storm!

Gallery

Inspired by these top tips? Have a look at our Photo Gallery and then have a go for yourself. As Kirk says, practice makes perfect! We’d love to see the results: you can email your best photo to us at hopelearning@oum.ox.ac.uk. Please make it clear if it’s OK for us to use it on this blog. We’ll also need permission from a parent or guardian to publish your name.

Photo Gallery

If you would like us to share one of your photos, please email it to hopelearning@oum.ox.ac.uk. If you want us to use your name in the image credit, we will need permission from your parent or guardian.

Raising Moths

Ben brought in some Poplar Hawk Moths to show the other participants at our recent summer school. Here he describes how he raised them from eggs he received as a gift from his grandfather.

Last year during lockdown my Grandpa gave me 32 hawk moth eggs: 30 eyed and two privet. Not the most common of presents you might think, but these turned into the most enjoyable gift. I was very excited as I tore open the parcel and found the eggs safely packed in a small tube. It took roughly a week for the leafy-green eggs to turn into the most delightful little caterpillars. I decided to call them all Jim. The first thing they went towards was the fresh willow that lay in a small, water-filled jam-jar.

Poplar Hawk moth caterpillar with Ben’s hand for scale. Photo credit: Ben Atwell

Immediately, they started taking chunks the size of their heads out of the leaves until there were no leaves left inside the tank. I was very surprised by how much they ate in proportion to their size. Every day they grew bigger until, within 4 weeks, they were the length of my index finger! They were bright green with white stripes, pink spots and little pointy tails. To help them grow, they shed their skins every few days. Sadly, one little Jim got stuck in his skin whilst shedding and died. Willow-collecting took a lot of effort as it involved daily trips to the canal, but this was a welcome break from staring at my computer all day during online school.

Poplar Hawk Moth larva feeding. Photo credit: Ben Atwell

One morning we found that a lot of the caterpillars were wandering around, banging their heads on the bottom of the tank. They were also turning a darker green which (after a bit of research) we found out meant they needed to bury and become a chrysalis. We put a deep layer of soil into the tank and within minutes they had disappeared. We tucked them up in the shed for winter and waited.

After months of hibernation, they started emerging this spring with crumpled wings, looking very like dead leaves. After stretching out their wings we noticed that we couldn’t see the eyes that the eyed hawk moths are known for, but as we later realised, they only show the eyes as a defence mechanism if they were under attack. Normally it would take a while for the males to seek out the females using their fanned antenna, but because they were in a large tank, it was easy for them to find each other and mate. Within a few days they had laid over 1,000 little green eggs! So, the process of willow collecting began again, but this time, after checking with the county moth recorder, we released the little caterpillars (who this year I called Jeff) into our local wildlife reserve, hoping that they survive and go on to repeat the process in the wild this year.

Poplar hawk Moth adult. Photo credit: Ben Atwell

We are still waiting for the privet chrysalises to hatch, but to keep me busy, my Grandpa sent me 15 poplar hawk moth eggs this spring. These have already been through one cycle of eggs-caterpillars-chrysalis-moth-eggs and I gave some of the eggs to the museum during the Insect Investigators Summer School. I hope the staff have time to collect all that poplar!

The Poplar Hawk Moth, Laothoe populi, is a beautiful insect found thrououghout the UK and is common wherever their foodplants can be found: mainly the poplar trees from which they get their name, aspen and willows. Ben describes the voracious appetite of the larvae well. The adults don’t feed at all and so are short-lived. You can find the adult moth from May to July and the caterpillars from June to October. In Southern England there may be a second generation of adults in the autumn.

Make a butterfly feeder

In the last post Kate told us all about her favourite butterfly. In this post I will be showing you how to make your own butterfly feeder, from items you might commonly have at home, to help attract butterflies, and other insects, to your outside space. I had to raid my recycling bin for key materials.

Here are the same instructions on how to make a butterfly feeder, as can be seen in the video:

What you will need:

  • Cardboard
  • Coloured pens or paints
  • String or wool
  • Glue or sticky tape
  • Scissors
  • Bottle top
  • Hole Punch
  1. Take a piece of cardboard and draw a flower with five petals, roughly 20cm wide.
  2. Decorate your flower in any way you wish.
  3. Cut out your flower.
  4. Fix the bottle top to the middle of your flower using glue or sticky tape.
  5. Use a hole punch to make a hole at the edge of each petal of your flower.
  6. Cut five pieces of string or wool, each roughly 40cm long.
  7. Tie the five pieces of string together at one end.
  8. Turn your flower over and thread a piece of string through each hole, and tie the five pieces of string together.
  9. Tie an additional piece of string, or wool, to the knot.
  10. Hang your butterfly feeder in a sunny, but sheltered, spot outside.
  11. Mix together sugar and water, or take a small piece of overripe fruit (e.g. orange or banana), and put it in the bottle lid.

Watch to see any butterflies, or other insects, that visit your feeder. You could investigate which foods different species prefer.

Please tell us about your butterfly feeders and investigations. We would love to see photos of them. Contact us or email at hopelearning@oum.ox.ac.uk.