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Most of the species recording in the Garden involves finding out what species have come into the Garden of its own accord, but there are sometimes special circumstances enacted behind-the-scenes to attract certain species to lay their eggs... Poulomi Bhadra explains:

 

"The Wildlife Garden in the summer is thriving with flora and fauna and provides excellent grounds to study the attraction of blowflies to bodies in suitcases. As part of my Masters project at King's, I am investigating blowfly behaviour and particularly their ability to lay eggs without being in direct contact with a food source. This is part of the research conducted by the Museum’s forensic entomologist Dr Martin Hall in collaboration with the Metropolitan Police.

 

Even though preliminary experiments have been conducted indoors in a laboratory at the top of the Southwest Tower (where the smell of decomposing chicken liver wafts undetected above the crowd of visitors in the rest of the Museum!), it was necessary to see if the results could be replicated in field conditions.

 

After several failed efforts to protect the experimental set-ups from the resident foxes - who were evidently attracted to the smell of meat and often stole my experiments - we succeded in a set-up consisting of a dog cage that was enclosed in chicken wire.

 

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Dog cage set-up - weighted down to deter foxes!

 

Petri dishes containing meat, and sealed by a zip, were laid out in the dog cage and behind-the-scenes in the Garden to see if any blowflies would be attracted to them and lay eggs. As it turns out, populations of bluebottles (Calliphora vicina) and greenbottles (Lucilia sericata) visited the cages as soon as they were placed.

 

DSC_0033 (Custom).JPGBlow flies were immediately attracted to the experimental bait

 

The experiment was collected the next day and white dipteran egg clumps were seen to have been laid on the tape of the zips, which had been moistened by the blood and decomposing fluids from the liver beneath. Eggs were also deposited in between the teeth of the zips and when the baits were dismantled in the laboratory, egg clumps were seen hanging like stalactites on the underside of the zips.


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Twenty-fours hours later fly eggs were found laid on the zips

 

This is possible because blowflies lay eggs through ovipositors, which are located at the end of their abdomen. When laying eggs, this ovipositor extends outwards like a lance and can get inside and through crevices, such as the gaps between the teeth of a zip, so that the female is able to drop her eggs.

 

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Female flies extend their ovipositor into gaps to lay eggs in clumps

 

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Calliphora vicina laying eggs on zips in the laboratory experiemental set up

 

During the especially high temperatures this summer, most of the eggs hatched within 24 hours and the first instar larvae, 1-2 mm long, crawled their way through the gaps in the zip to feed on the meat below. The eggs collected from these trials were reared to adulthood in the laboratory.The species that oviposited (laid eggs) predominantly was found to be the bluebottle, Calliphora vicina. Only four adults of the greenbottle, Lucilia sericata, were reared from the laid eggs, even though both species were present in the garden and trapped in the RedTop® flytraps hung nearby for collecting wild-type flies from the garden. 

 

In the beginning of August, a different experiment  was simulated in the field to study a case scenario: a pig’s head, purchased from a butcher's shop, was put in an airline cabin suitcase and then put inside the wired cage. Flies were seen visiting the suitcase regularly during daylight hours but no eggs were seen until the second day, when a single egg was laid on the cloth seam of the suitcase and near the zip. By the third day, more eggs had been laid between the folds of the seam and the zip and inbetween the teeth of the coiled plastic zip. First instars were seen later, travelling along the length of the zip around the suitcase.

 

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Simulation of case scenario - a pig's head in a suitcase inside the cage, left in this position for 3 days

 

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Flies deposited their eggs in between the teeth of the zip and the crevices of the zip slider and the larvae made their way through the zip to reach the food source inside the case

 

The suitcase was brought indoors after three days to avoid the malodours from the decomposition permeating throughout the Garden, which was open to the public. On the eighth day since exposure, third instar larvae were seen dispersing from the suitcase, looking for suitable grounds to pupate. When the suitcase was opened the bait inside was found infested with third instar larvae which meant that the adult flies, or hatching larvae, had been able to penetrate the completely closed zip to gain access to the food inside.

 

The experiment is still under study and we are looking forward to replicating a few more proof of concept studies to establish the potential for delay in egg laying, and to confirm the species that show most propensity of laying on enclosed carrion. The results from this research will have practical value in explaining the presence of larvae on bodies found inside suitcases and will help forensic entomologists estimate a more accurate minimum time since death for the bodies of victims who are disposed of in this manner."

 

Thank you Poulomi, we have enjoyed your company in the Garden this summer, but I can't look at a zipped suitcase in the same way again...

 

For more information about this work please see Museum's forensic entomology web page or come to this year's free Science Uncovered event on the evening of Friday 27 September and see our forensic enotomologists in person.

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One of the many rewards of returning to work in the garden after a short break is not only to see changes in the vegetation that have occurred but also to hear about the different species of insects that have been spotted recently. Here Larissa tells us about the vibrant butterfly life during two sweltering weeks in July:

“Just living is not enough," said the butterfly, "one must have sunshine, freedom, and a little flower.”

― Hans Christian Andersen, The Complete Hans Christian Andersen Fairy Tales

It’s my favourite time of the year and I have welcomed the heat after a cool spring. This spell of fine weather is particularly good news for butterflies, whose populations had suffered from the previous years’ wet and cool summers. Butterflies and moths are unable to fly, find mates, feed or lay eggs to maintain population levels when the weather is poor. They are sensitive to environmental changes, and because of this, they are seen as good indicators of the likely effects on other species from a changing climate.

 

The first to emerge in the Garden earlier in the year at the end of April, were the orange tip (Anthocharis cardamines). Both male and female butterflies were around so hopefully they have mated successfully and we shall see their return next year. The males have the distinctive orange tips on their wings from which they get their name while the female is less conspicuous, lacking the orange tips and distinguished from the whites by the green mottled underwing which she shares with the male.

 

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Orange tip - this male was hiding from the April chill earlier this year, in the warmth of our greenhouse. Photo © L. Cooper

 

Early May saw the arrival of the first speckled wood (Pararge aegeria) and the holly blue (Celastrina argiolus). The holly blue is a delicate and beautiful butterfly with their blue wings brightening up the early spring garden. It gets its name from its preference for holly (Ilex aquifolium), but it also lays its eggs on ivy (Hedera helix), especially the summer brood.

 

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Holly blue - while males and females differ slightly on the upper wing, they are less distinguishable on the underside. Photo © Peter Eeles, Butterfly Conservation

 

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Speckled wood - often seen sunning themselves on a log in the Garden's woodland areas, or around the shed. Photo © L.Cooper

 

There have been plenty of large and small whites (Pieris brassicae and Pieris rapae, respectively) around since spring, dancing together over our pond and in the meadow. Although common and seen as a pest to many allotment owners, you can’t deny their beauty when in flight.

 

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Large white - setting aside one or two cabbages for caterpillars, and removing them from the rest, could be a way to happily coexist with the small and large white butterflies. Photo © Tim Melling, Butterfly Conservation

 

But it’s these last two weeks in July which have been the most impressive. The arrival of the sun has brought more butterflies with it and it never ceases to amaze me just how much wildlife can be found in this little acre of green in the heart of London.

 

On the 15 July, I sighted the first visits of the year to the Garden from 3 different species. First up, a red admiral (Vanessa atalanta) passed me by near the pond resting just long enough in the reeds to admire its bright colours.

 

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Red admiral. Photo © Neil Hulme, Butterfly Conservation

 

The red admiral was followed shortly by a skipper flying around the hedgerow flower near the greenhouse. These were planted with the aim of providing a nectar source for insects so it good to see that it is working! Unfortunately, the skipper lived up to the reason for its name and was quick to fly away so I have neither a photo or species identification, but I think it was likely to be a large skipper (Ochlodes sylvanus).

 

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Large skipper - the members of this genus adopt a typical pose making it easy to identify them as skippers. Photo © Ian A Kirk, Butterfly Conservation

 

I then spent about an hour, on and off, trying to spot an elusive bright orange butterfly which kept tempting me, then flying away at the last moment. It looked too bright to be a British specimen at first and I thought it may possibly have been an escapee from the Museum's nearby butterfly house that is on the East Lawn for the summer. However, when it landed long enough for me to take the poor picture below, before it took to the wing and disappeared, I was able to identify it as a comma (Polygonia c-album). Although it was a first for me, it has been a frequent visitor to the garden in previous years and it is resident in the country.

 

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A comma - bigger than I imagined, but recognisable from the rough wing edges. The species gets its name from a white 'c' shape on the underside of its otherwise brown wing. Unfortunately, this one didn't stop for long enough for me to capture this signature marking. Photo © L. Cooper

 

A couple of days later, not only did our new volunteer Alora spot the first six spot burnet moth of the year but a little while later we had a Garden first. A ringlet (Aphantopus hyperantus) settled in the meadow long enough for us to take a picture and identify it by the distinctive rows of rings on the underside of its wings (n.b. they do also have rings on the upper wings). This was a very exciting day!

 

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Ringlet - not only a first for the Garden but also an uncommon species in London. Photo © N. Lake

 

 

Today I can also add a brimstone (Gonepteryx rhamni) to the list of my sightings, feeding on purple loosetrife nectar by the Garden’s waterfall.

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A brimstone feeding - my first sighting of the species was earlier this year at Juniper Hall. It’s lovely to see them here in the Wildlife Garden too. Photo © L. Cooper

 

I’ll keep looking for butterflies this summer, and you can also join in with Butterfly Conservation Trust’s Big Butterfly Count. It’s the world’s largest butterfly survey and by taking part you can help monitor the health of our environment. The Big Butterfly Count is really simple and great for all ages, and even comes with a free easy to use smartphone app to help you’re your recordings. To find out more visit the Butterfly Conservation website.

 

Thank you Larissa!

 

P.S. Drop by the Garden to see if you see some of the same butterflies as Larissa or, to see exotic butterflies and moths that aren't native to our shores, visit the Museum's Sensational Butterflies exhibition. It's in it's last few weeks so be sure to come along before it ends on the 15 September.