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Curator of Diptera's blog

3 Posts tagged with the maggots tag

So Last week I performed a HUGE 9 minute set for a Museums show off. People from all over the museums and libraries sector come and present a skit on something about their work or their museum. Now I choose to highlight the wonderful creatures that are maggots. They are all over my desk, I get sent them in the post, yesterday I, alongside a colleague, were hunting for them in the wildlife garden, I was rearing them from poo in the towers – in fact, maggots are very dominating in my job. And quite rightly so.


So I thought that I would convert that into a blog about these fantastic things and why the collections and the staff at the Natural History Museum are so important with maggot research! I have briefly touched upon maggots before but i thought that I would go into some more detail.



Let’s first clarify what a maggot is. The term maggot is not really a technical term and if you type in ‘what is a maggot’ on Google you get this!


maggot definition.jpg


To this date I have never heard someone describe something they yearn for as a maggot but who can say what will happen tomorrow with language fashions.


The maggot is a juvenile or, as I prefer to call it, the immature stage of a fly. These vary in form across the order from the primitive groups of flies (Nematocerans) to the more advanced groups (Brachycerans). The primitive groups have a more defined form in having a distinct head capsule with chewing mouthparts and we refer to these as Culiciform (gnat shaped).


mossi larvae.jpg A mosquito larva which is culiform (gnat shaped).


Those more advanced flies whose larvae are without a head capsule and mouth parts that have just been reduced to hooks are called Vermiform (literally meaning worm shaped); and it is the later group that we generally call maggots!


blowfly maggots.jpgA slightly more informative picture of some Vermiform larvae - the maggots of a blowfly.


We can label describe these head capsules further into three types;

  • Eucephalic (distinct capsule and mandibles)
  • Hemicephalic (incomplete capsule and partly retractable mandibles)
  • Acephalic (no distinct capsule with mouthparts forming a cephalopharyngeal skeleton)


trichoceridae larvae c Matt Bertone.jpgA trichoceridae larvae (eucephalic) © Matt Bertone.



dipteraathericidae hemicephalic.jpgAn Atherceridae larvae (Hemicephalic).



And a housefly maggot (Acephalic larvae).



However for the purpose of this blog I will use the term maggots to include all Dipteran Larvae as there are some very important (and incredibly attractive) larvae from some of the more primitive groups. And they differ from most other insect larvae by the lack of jointed legs on their thorax. Beetles larvae are grubs, Butterflies and moths are caterpillars, bugs just have mini-versions of the adults, but they all have jointed limbs.


tipulidae drawings.jpgAbove are some of the more incredible images of a cranefly larva. But these are not the heads of the cranefly larvae but rather their anal or posterior spiracles (breathing tubes). Anytime I need cheering up I flick through images of posterior spiracles.


cranefly-larvae-resize-12feb14.jpgMost people just view the larvae from either above or parallel but these are from bottom on! (these above diagrams are from the brilliant book by Kenneth Smith on Identification of British Insects) but as you can see some of the more interesting features are from this angle.


These spiracles form part of a breathing system that enables the maggot to breathe whilst feeding. These vary across the fly group with there being 7 different set ups of the spiracles.

maggot-spiracles--resize-12feb14.jpgLocation of spiracles on the body of a maggot, shown with dots and circles.


The above diagram from top left to bottom middle shows (by dots and circles) where the spiracles are on the body. Some systems are very common such as the amphinuestic set up being found in most Diptera whilst others are very specialised such as the proneustic systems (only found in some fungus gnats). Some of them have taken their spiracle and run with it (as it were). Check out the rat-tailed maggot below (larvae of a hoverfly).


rat tailed maggot.jpg

Rat-tailed maggot (larvae of a hoverfly).


The mouth can concentrate on ingesting food solidly – just imagine 24/7 eating. Now the maggot stage is the one designed for eating. I often wonder what it would be like to have the lifestyle of a fly – born, eat, eat, eat, eat, eat, mate, die…..and therefore they don’t have to have all of the equipment of the adult.


As I have already mentioned the larvae of Diptera do not have legs as other groups do such as the moths or the ants. This is because they are highly specialised examples of precocious larvae i.e. examples of very early hatching. And this is what arguably has lead to the most diverse range of habitat exploitation of all insects. They are plastic; they can squeeze themselves into tiny holes and between surfaces and therefore take advantage of so many different food sources.


In the wonderful book by Harold Oldroyd – The Natural History of flies - there is a sentence that states that the larva and adult are more different from each other than many Orders of Insects. And so in many ways with many species you could argue that flies fit two lifetimes into one as they are often completely different, both in form but also in diet and habitat.


Maggoty enquiries


The Diptera team have been talking maggots a lot recently. One of us, Nigel Wyatt, is something of an expert already on most things maggoty, working on most commercial, consultancy and public queries relating to maggots.


I had one recently from a friend of mine. She is a vet and one of her colleagues works with Police Dogs. Her colleague was a little confused and concerned about a maggot that was defecated by one of the dogs as she had not seen one so large before. My friend immediately thought of me and sent it to the Museum in a little tube of alcohol. Despite the alcohol it was quite fragrant by the time it arrived on my desk but it was easily identifiable as a cranefly larvae. Now cranefly larvae are incredibly versatile in terms of their habitat – they live in moss, swamps, ponds, decaying wood, streams and soil but as I far as I know the inside of a dogs alimentary canal is not a known habitat. They consume algae, microflora, and living or decomposing plant matter, including wood and some are predatory but parasites they are not. This one had miraculously come through the entire digestive tract of a dog without being destroyed. No harm done except to ones nasal cavities.


However, cranefly larvae or leatherjackets as they are sometimes called have caused some problems to lawns due to them consuming grass roots. Wikipedia – the great font of scientific knowledge cites from Ward’s Cricket's Strangest Matches ‘In 1935, Lord's Cricket Ground in London was among venues affected by leatherjackets. Several thousand were collected by ground staff and burned, because they caused bald patches on the wicket and the pitch took unaccustomed spin for much of the season.’


Apart from the staff who help with identifications we are helping further with outreach by helping with development of a new, hotly awaited book on British Craneflies. Alan Stubbs (not the retired footballer but the rather more impressive Dipterist and all round Natural History Good Egg) and John Krammer (retired teacher and superb Cranefly specialist) have been working on this fantastic tome for a while now and we have all been trying and re-trying the keys to ensure that they work. Preparations of gentailia, wings and larvae have been undertaken at the Museum on both Museum specimens and ones donated by John, and images and drawings of these been done. Carim Nahaboo has been drafted in for some of the drawings so expect great things.


This is an adult Dolichopodidae but it is a fine example of Carim Nahaboo's artwork.


Flies and their offspring have a terrible reputation. People are disgusted by most of them. However, they are essential both for our health and habitat but also for telling us what is happening.


Dr Steve Brooks and his group at the Museum work on Chironomidae (non-biting midges), and more specifically the immature stages – their larvae. Chironomid larvae are quite primitive and as such have a complete head capsule which is … as the larval stages develop they shed their head capsules and grow new ones, and these discarded ones can be used to determine the environmental conditions of the habitat both now and in the past as well as monitoring heavy metals.


hgrimshawi-48125-1.JPG Head capsule of a chironomid, which can be used to determine past environmental conditions.


I first came to the Museum as a professional grown up thanks to Steve as I was conducting a study using Chironomids as indicators of environmental health as they are fantastic bioindicators. Many Chironomid species can tolerate very anoxic environments as they, unlike most insects, have a haemoglobin analog which is able to absorb a greater amount of oxygen from the surrounding water body. This often gives the larvae a deep red colour which is why they are often called blood worms. Although slightly fiddly as you have to dissolve the body in acid, the use of head capsules for identification (image above) is fairly straight forward. The little crown like structures that you can see are actually rows of teeth and these are very good diagnostic features. Steve has worked for a long time on the taxonomy of these species and his (and his groups) expertise has been used globally.

So as well as looking funky we can use them to tell us many things about the world of today and yesterday. More on maggots in the future.


This blog article comes with a warning - for some reason my tolerance for what some may describe as revolting and distasteful seems to be very high. In fact I view those subjects that most people feel squeamish about as truly interesting - I think that nature is ingenious! So, in light of that forewarining, I will proceed…


I think that we are all aware that insects are great ... really great, attractive, adaptive, specialised little packages of wonder. And one thing that we should be ever so thankful for is that an awfully large number of them are decomposers. That is, they break down bodies ranging from large corpses to fallen leaves. And it’s not just the dead bodies that they break down - thankfully they remove waste too - so, think about a world without insects where we would be knee-high in faeces.


Many adult insects have developed novel ways to ensure that they are ready and waiting for fresh dung. Instead of locating freshly deposited material (I hope that you are not eating at the moment …), many species of beetle cling on to the ‘host’ and wait for them to defecate so that they can then fall off alongside their food. Check out the photo below with a family group (see doesn’t that sound cute!) of beetles clinging on to a monkey's nether region!


monkey bum.jpg

If you think this is extreme spare a thought for the poor dung beetle that hangs onto the backside of a kangaroo...
(Taken from Jacobs et al, 2008)




Sometimes insects take this life cycle a little too far even for me!



(From Encyclopedia of Entomology by John L. Capinera)



But let's get back to the main emphasis of the blog: flies and beetles are exceptionally valuable decomposers. The decomposing of animal and plant material is essential to ensure that there is a flow of nutrients round our ecosystems. When it’s not waste products, it's dead bodies. And that is what I want to concentrate on here today - what the flies do and how we can utilise this. Can you even begin to imagine what it would be like if there were not flies to break down the bodies of all shapes and sizes that would be littered around?


For the second episode of BBC Radio 4's Who's the Pest? I interviewed forensic entomologist Dr Martin Hall (aka Maggot Man), who works with me here at the Museum. 


Martin Hall plus mosquitoes - Bolivia.JPG

Maggot Man, Martin Hall, taking his work with flies very seriously! 


He’s a brilliant man and he is not alone in working on insects (specifically flies) and their use in forensic entomology. In the department there used to be Maggot Boy - but sadly his postdoc has come to an end - and there is also Amoret Whittiker (not Maggot Girl!). Amoret has recently been the star of the Radio four program The Life Scientific and if you think that I have some strange quirks ... She has also been described thanks to her work on forensic entomology as a Superhero of Science - something to aim for!


The maggot is a common name for the larval stage of the fly and is generally associated with the more advanced flies, such as the houseflies and blow flies. In his fantastic books called the Natural History of Flies, Harold Oldroyd described maggots as precocious because they emerged earlier from the eggs in comparison to most insects, and are more plastic in terms of their structure. This feature has enabled maggots to get into and survive in an enourmous range of habitats.


The field that Martin and Amoret work in, amongst others, is that of forensics and this has become oh so popular since the advent of TV series such as CSI and Prime Suspect, but the use of insects to help determine the time of death is not a recent phenomenon. At the Museum we have a famous jar of maggots (not often I get to put that into a sentence) that was a sample from the first successful use of insects to tie a murderer to a victim! This story begins with Dr Buck Ruxton, who was a practising GP in Lancashire in the 1930's and was generally well-liked and respected within the community within which he lived and worked:


The rather dapper Dr Ruxton


Then, in September 1935, the bodies of his wife and maid turned up in small ravine miles away in Dumfriesshire, Scotland. He claimed that his maid had fallen pregnant and that his wife had run away with her to assist with an abortion so it couldn't have been him that killed them, guvnor. However, he was a sloppy man! Although their bodies were chopped up to make it more difficult to identify them, there were maggots still associated with the limbs and these were aged by Dr A.G. Mearns.


This provided a vital clue as to when the murders took place and it was this, coupled with the damning evidence that one of the newspapers used to wrap body parts was only found in Dr Ruxton's local region and not where the bodies were found, that led to the 'good' Doctor being found guilty and subsequently hanged.


So, you can see why they are precious maggots to us! For nearly 80 years we have been using insects as indicators of when and where death occurred to assist us in criminal proceedings in court, and we have long known about their effectiveness at turning up at the scenes of dastardly deeds.


In fact the ability to locate dead bodies is marvellous, and of primary importance are the flies from the family Calliphoridae, the blow flies. These include the common flies - the green bottles and the blue bottles - and many are very large and metallic-looking ... and arguably very attractive! These flies are always the first on the scene and they have an amazing ability to smell - they can detect a fresh corpse from up to 16 km away!



How can you not but admire this beautiful little creature? A Chrysomya megacephala male


Now, we know that these types of flies only lay their eggs on dead material so the maggots only develop after death (maggots living on live flesh is a whole different but interesting subject ... and really not for the faint-hearted). So, if we find maggots that are five days old, we can confidently say that the minimum postmortem interval (PMI) is five days - i.e. death could not have happened less than five days previously (it could be more, but it can't be less). However, under different conditions and differing temperatures, the development rate of the maggots varies and this is why we are still studying these species. And we know this because researchers have been working on the development rate of these flies for years and years.


Martin and Amoret have at times had decomposing material in the tower at the Museum (this has sometimes resulted, in the dead of winter, an enormous blue bottle winging its way down the stairs to come and say hello to the rest of us whilst we have our lunch; very friendly I thought). Up in the tower they are creating different ambient conditions to enable them to work out how this affects the developmental rate of the maggots and therefore more accurately determine time of death.


This idea is being used on a much grander scale in America where, in Tennessee amongst other places, there are facilities where people have donated their own bodies(!) after death to enable in-depth research into the decomposition processes. The Forensic Anthropology Centre, more colloquially known as the body farm is one such place.


The facility is located in an area of secluded woodland where there are many different experiments performed to look at the impact of different environmental factors on decomposition. Amoret herself conducted some experiments here to determine how comparable pig and human decomposition was (it is!) and I recently attended an entomology conference in Knoxville and listened to lectures from many forensic entomologists that either work there or utilise the knowledge that it generates.


So the fly that everyone goes 'ugh!' at is in fact an incredibly useful agent of the law in addition to its being a rubbish disposal unit and a 'keep the community tidy' advocate! Brilliant things - I have long been fascinated with maggots and their fantastic adaptability to penetrate so many different feeding niches!


Listen to Who's the Pest online at the BBC website


Let there be maggots...

Posted by Erica McAlister Jun 25, 2012

Well the one good thing about the weather being so awful is that is has forced me to be desk bound and so I am finally getting round to sorting material from previous field trips (both mine and other material that has been donated).  This has been both dry material that has been pinned and wet samples that have been collected some way or another into alcohol. There is nothing quite like the smell of stale alcohol on your fingers...


One of the projects with loads of material is in collaboration with the soil biodiversity group within the Museum and their volunteers (we love our volunteers!). The NHM have been sampling in the New Forest for many years now collecting soil surface invertebrates from Winkler bags.



Image from


Material, such as leaves, is placed inside the trap and the insects etc gradually fall down into the collecting pot below. It is a passive way of sampling for insects and you can collect from a known area so make very good cross site comparisons. However, from the samples, certain groups were ignored, deemed too difficult for non specialists to deal with. This is hopefully were team Diptera come in! We are trying to develop a simple key for New Forest Diptera larvae to enable the team of volunteers to be able to go through these groups.


The larvae are important as they contribute much to the break down of leaves and therefore nutrient recycling. However, there are huge gaps in our knowledge of fly larvae – the Dipterists Forum state ‘at present it almost seems that most adult flies arise by spontaneous generation, as was commonly believed two or three hundred years ago!’ because of this lack of knowledge!!


Nigel Wyatt, resident specialist in all things maggoty spent some time last week teaching the rest of us lesser mortals the finer details of identifying specimens with limited features:



Kim, Nigel, myself and new recruit Duncan.


Although this is not the clearest of photos it does show us all happy. This is because Nigel was here to help us. When he left we fell apart and struggled to identify anything further!!!!! Ho hum...


However there are a few that are just very bizarre…


cranefly larvae.jpg


What is not obvious about the above image is that is it's posterior end of a crane fly larvae ... I will not say anything more on the subject on the grounds of public decency ...


But the tears will hopefully be worth it. This project is part of a much wider one trying to develop a larval collection for British Diptera as there are limited such collections, except with the aquatic larvae (but even then it is not exhaustive). In doing so we have been routing around the main spirit collection to see where there is any room - the problem with doing this though is that I tend to get myself side-tracked by other jars of really interesting specimens.


The spirit collection is jars in trays on shelves in cabinets looking suspiciously like this….



The samples shown here are from various trapping events from the past that still need to be sorted. We have several cabinets and know that we are probably sitting on much undescribed material.


However, below these traps were some random jars. Check out these wonders:



A lovely jar of bot fly larvae - what more could a girl ask for?


Or what about this one:



Please excuse the blurred picture but I was probably over excited at the time with my finds. These are some more flies with the very small eggs at the bottom, on top of them are the larvae and then the top layer is the adults - granular convection before your very eyes (the brazil nut effect where the large nuts always end up at the top).


So a picklers life for us for a while trying to sort this all out

Erica McAlister

Member since: Sep 3, 2009

I'm Erica McAlister, Curator of Diptera in the Entomology Department. My role involves working in the collection (I have about 30000 species to look after and over a million specimens), sometimes in the lab, and thankfully sometimes in the field.

View Erica McAlister's profile