Picnic Invaders!

Here in the Britain we are currently experiencing what is fondly known as the Great British Summer, a season of sunshine (sometimes), barbecues, pub gardens and picnics. However, it is not just people marking these events on their calendars, insects have been looking forward to joining the festivities too.

Broadly speaking, the most common, uninvited, six-legged visitors to our outdoor activities are ants, wasps and flies. Their mere appearance can send people in to a state of terror; some people flail and flee from the insects while others stand brave with a rolled newspaper or, braver still, a bare hand raised like a fleshy paddle of doom!

Whether they were invited or not these little critters are here to stay, so what kind of hosts would we be if we didn’t get to know a little bit about them? To begin with let’s find out who they are; both the ants and wasps you encounter belong to the same order of insects, Hymenoptera. The Hymenoptera are a huge order of insects with over 100,000 described species (Meyer, 2009). The most common ants in Britain are the black garden ant, Lasius niger, and two commonly confused species both going by the name “red ant” Myrmica ruginodis and M. rubra. The most common species of wasp you are likely to encounter in Britain is the common wasp, Vespula vulgaris.

While they may look different these species all have something in common, they are eusocial insects meaning that they live in large groups in hives and nests. These hives and nests are populated with different “castes” of insect, in British species there are 3 castes; the workers which we are all familiar with, the queen(s) and, in the mating season, males. All Hymenopterans reproduce using a haplodiploidy system meaning that males can only develop from unfertilised eggs and so are haploid; as they have only the chromosomes of their mother they have no father!  While females develop from diploid eggs meaning they have both the chromosomes of their father and mother and are 75% related to their sisters! This unusual method of reproduction is often pointed toward as the reason for eusociality and is called the kin selection theory. The kin selection theory in a nutshell is: by working together to protect the nest and raise queen larvae infertile worker females can still pass on 75% of their genes through their sisters when the new queens emerge. Meaning their genes are passed on along with the added benefit of living in a group. Some species of Hymenoptera have more than one egg laying queen in a nest, in relation to our ant species, Lasius niger  nests are monogynous meaning there is only one queen while Myrmica rubra nests can have 2 or more queens .

In comparison to our next insect, ants are small fry. Nothing elicits summer time fear like the common wasp, Vespula vulgaris. These guys have a fearsome reputation hinged on their weapon of choice, a modified ovipositor. Their sting. The venom administered through this sting is made up of a variety of enzymes and proteins, as with all allergies it is the proteins that cause the allergic reactions. To date there have been 3 proteins identified as allergenic in V. vulgaris as outlined by Winkler et al (2003). Despite their reputation, the sting of the common wasp packs just 25% to 35% (2 µg – 15 µg) of the punch of the European honey bee’s (Apis mellifera) 50 µg! (Glaser, 2013). The difference is that bees can sting just once while wasps can sting repeatedly and wasps release a nasty pheromone alerting nearby wasps and encouraging them to join the attack.

So as terrifying as the wasps may be it is in your best interest to leave them alone and try not to panic as this makes stinging incidents more likely. Common sense reigns supreme in avoiding wasps; don’t leave food containers open when outdoors, try to avoid setting up camp if you notice a lot of wasps/flying insects nearby, avoid bright coloured clothes as this attracts wasps and try not to kill any wasps if it can be helped as this also stimulates the release of the “revenge pheromone”, I made that name up but the pheromone is very real. Wikihow has some unusual methods for deterring/killing/avoid wasps including a DIY bottle trap. I haven’t tried these personally but I’ll put a link at the bottom for anybody interested. Evidence has shown that wasp numbers are actually lower this year due to 2012’s abysmal summer (BBC, 2013) so you’re probably going to get very little trouble from these guys this year anyway.

Image

1. Male, 2. Worker and 3. Queen. 4., 5., and 6. Are Hornets.
The above image is a plate taken from The Observer’s book of common insects and spiders, the book is ancient but I liked the plate! I’ll reference the book in case you want to look it up but I don’t think it’ll be easy to track down.

 

Finally we move on to our last summer pest, these guys are more irritating than they are dangerous. The only real danger comes from their poor dining etiquette. We are, of course, talking about flies. More specifically blue bottles and green bottles or blow flies. Blow flies belong to the order of Diptera, a huge order of insects known as the “true flies” the number of species in this order  is thought to be over 200,000 outnumbering the hymenoptera by over 2:1! The number of described species is, similarly to Hymenoptera, at around 100,000 (Meyer, 2009 b). Even the common names blue bottle, green bottle or blow fly refer to many species. Blow flies belong  to the family Calliphoridae of which some of the more common species are Calliphora vomitoria, Calliphora vicina (blue bottles) and Lucilia seracata (green bottles).

Blow flies are generally attracted to rotting matter, excrement and food which makes for an unpleasant mix. The pathogens transferred to our foods by the flies can be almost limitless depending entirely on what the fly picked up at its previous stop! The flies commonly act as vectors for Salmonella spp., Escherichia coli and dysentery. The pathogens are carried on the bodies of the fly and in the digestive fluids they “spit” on to food in order to break down the proteins to be sucked back up.

Blow flies, like all Dipterans, possess only 2 wings as opposed to the 4 wings found in bees or wasps. Their second pair of wings are highly modified in to organs called a halteres, which acts as a counter balance while they are in flight which is why flies are so adept at moving in the air comparing to bees and wasps.

Image

1. Helophilius pendulus, hover fly 2. Physocephala rufipes, Thick-headed fly 3. Volucella bombylans, hover fly 4. Lucilia caeser 5. Calliphora vomitoria, female.
Again, taken from The Observer’s book of common insects and spiders

I’m aware this post is growing quite long now so I’ll cut to the final section, methods to deter flies from your outdoor activities (without using the obvious sprays, fly paper and other artificial means)! One of the most common methods is to hang a bag of water in a room/area you want flies to avoid, the theory being the refraction caused by the water confuses the flies. Sadly, this doesn’t work. As tested by Mythbusters on Discovery Channel, the flies just didn’t care whether a bag of water was present or not, I’ll link to the episode below.  After some googling I found there is some evidence that some herbs can act as a deterrent for flies, including basil, lavender and bay leaves amongst others.

That’s about it for this post, hope you’ve enjoyed reading and our next topic will be exploring the gruesome world of Forensic Entomology! If there’s anything you’d like to see me write about let me know in the comments below!

Further reading – if you enjoyed any or all of this blog post I’ll link to some articles around the web that might be of interest.

An Introduction to Eusociality – http://www.nature.com/scitable/knowledge/library/an-introduction-to-eusociality-15788128

The genetical evolution of social behaviour – http://joelvelasco.net/teaching/167win10/Hamilton64b-thegeneticalevolutionofsocialbehavior.pdf

A handy Dichotomous key to British ant species – http://antnest.co.uk/types.pdf

Wasp prevention and killing techniques – http://www.wikihow.com/Keep-Yellow-Jacket-Wasps-Away

Fly detterents – naturehacks.com/herbs/5-herbs-that-repel-flies/

Mythbusters episode 156, Bug Special – http://dsc.discovery.com/tv-shows/mythbusters/videos/bug-special.htm

 

References

Winker, B., et al, (2003), Allergen-specific immunosuppression by mucosal treatment with recombinant Ves v 5, a major allergen of Vespula vulgaris venom, in a murine model of wasp venom allergy, Immunology. [Online] 110 (3) P. 376 – 385 Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1783061/ [Accessed: 05/07/13]

Linssen, E. F. & Newman, H., (1973), The Observer’s book of common insects and spiders. London: Frederick Warne & Co Ltd.

Glaser, D., (2013), Wasp Stings, Insect Stings. [Online] Available from: http://www.insectstings.co.uk/waspsting.shtml [Accessed: 05/07/13]

Meyer, J. R., b (2009), Diptera. [Online] North Carolina State University. Available from: http://www.cals.ncsu.edu/course/ent425/library/compendium/diptera.html [Accessed: 05/07/13]

BBC, (2013), Who, What, Why: Where are all the wasps?, BBC News. [Online] Available from: http://www.bbc.co.uk/news/magazine-23356578 [Accessed: 20/07/13]

Meyer, J. R., (2009), Hymenoptera. [Online] North Carolina State University. Available from: http://www.cals.ncsu.edu/course/ent425/library/compendium/hymenoptera.html [Accessed: 05/07/13]

 

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One response to “Picnic Invaders!

  1. Pingback: Stinging Insects Infographic | Pest Control and Bug Exterminator Blog·

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