Q&A with Rentokil entomologist Matthew Green
Summer brings bees, wasps and ants out in force, and bed bugs, fleas and other pests can be a year-round annoyance. Step forward Rentokil entomologist Matthew Green, to answer questions about all things biting, stinging, hopping and generally bugging.
Fruitshootsandheaves: There seem to be a lot more wasps about this year, and a lot earlier. Why is this?
Matthew: Annual variations in social wasp population numbers are still not completely understood. Spring weather conditions seem to play some part in determining the density of adult wasps in the summer months, but some researchers have found evidence to suggest that is not the only factor at work and there is some element of density dependence that causes wasp numbers to fall once local numbers of wasps reach a certain point. More information here.
ViolaTricolor: I'm pretty sure we have a wasps' nest under our house in an airbrick, as there are a lot of them coming and going. They aren't in a place where they bother us, and I am pretty averse to killing things unnecessarily. I like the fact that they kill other insects and we're not allergic to stings. So, is there any reason why it's a bad idea to just leave it alone, as long as we're careful, given that they won't use it again?
Matthew: It's conceivable they might use it again, it depends how much room there is. If they are not causing you a problem, they are not pests (to you). Feel free to leave them alone.
Seedlessgrape: What use do wasps have, either in the food chain or in nature?
Waltons: What on earth are wasps for? Do they serve any useful purpose in the overall scheme of things?
Matthew: Wasps are predatory insects; they perform a similar role to other predatory insects (including dragonflies, ladybirds and hoverflies). Remove wasps from an ecosystem and you would see a rise in the insects they feed on. They are pretty important beneficial insects in agriculture as they feed on a number of crop pests.
scrappydappydoo: I have two daughters (aged five and three) who are terrified of buzzy flying things - everything that flies is deemed a 'bee' accompanied with lots of screaming. It gets very tiresome. The situation has not been helped by my youngest being stung by a wasp last summer. We are going camping in August and I'm dreading it - any tips for keeping them away? Does a jam jar really work?
Matthew: Good hygiene is the basis of good pest control, so make sure that all litter is tidied away quickly and kept in a sealed bag. Clean up any spillages promptly, too. Jars of sweetened water will hold a visiting wasp's attention, although jar traps work best when the wasp can't work out how to get out again. You can buy jar traps with narrow necks or make your own.
Pseudonomic: Why can't Rentokil just kill all the blinking wasps once and for all?
Matthew: There would be far-reaching implications for the food chain.
Fluffyanimal: Do all species of bee sting, or is it only honey bees?
Matthew: Not all bees sting, but bumblebees can do.
Kveta: Is there a child-friendly way to get rid of them from the garden? I have been putting down permethrin powder every time a nest crops up, but they don't seem too fazed by it, and just sprout another nest a few yards away every time. I wouldn't ordinarily be fussed by them, but my son frequently comes into the house coated in them, which is not pleasant.
WhipMeIndiana: We keep getting two or three odd ants in the conservatory and into the lounge. Is this because they smell food? What are they doing? Exploring for the main bunch? How can we really deter them from coming into the house in a toddler-safe way?
Earwiggy: Last night I noticed lots of big flying ants in the kitchen and realised they were coming out from under the fridge. On pulling it put out I found sand piled up to the skirting boards, 2" deep. We shovelled it out and didn't find many more ants, so perhaps not the nest itself? The ants appear to be nesting under the patio directly outside the kitchen but we can't tell where they are coming from. Is this activity likely to damage our house and why are they leaving piles of sand in our kitchen?
Matthew: Garden ant nests can remain active for well over five years. Digging up the nest is an effective non-chemical way of dealing with it, provided you can get to it. It's impossible to a make a building 'ant-proof', so you will always find one or two ants looking for food. Try putting down some double-sided tape on the floor where you suspect they are coming in. They should get stuck and you might find some appropriate places to improve proofing or apply baits.
For more information about why ants fly en masse and why they turn soil into powder, visit the Rentokil blog.
Kveta: Do you still love insects after years as an entomologist?
Matthew: I still love working with insects. I went to one of my old university's career days earlier in the year and one of the students asked how I reconciled being interested in insects and killing them for a living. I view my role with Rentokil as trying to educate people about insects, the same as any other entomologist (not that it's a popular career choice), we only resort to insecticides when a situation is out of the control of the client.
Reducing the insect population and promoting good hygiene and cleanliness is the basis of good pest control. After all, insects are only pests if they are bothering you, if you understand why they are bothering you and make an effective change, they will cease to be pests.
HauntedLittleLunatic: I have a 10 year old who is petrified of flying /creepy crawly things - even butterflies. Any tips to help her?
Matthew: My wife is afraid of butterflies and moths; I often suspect she married me for free 24-hour moth removal. I think some children pick up their fear of insects from their parents or other folk they spend a lot of time with: my nine-year-old asks to come into the lab to hold the cockroaches.
To conquer her fear, start with the big stuff and work downwards. Museums with displays of massive insects are a good place to start. Goliath beetles, Atlas moths, giant stick insects and other invertebrates of that scale are good to look at - everything else is smaller and less scary by comparison. If you can find places that will let you hold things like that it's even better.
A lot of the time the large insects are very boring, they will sit still and not do very much (usually whilst a petrified child sits, quaking, with a hand held out and their head buried in their shoulder). You could try to look out for the prettier end of the insect world in books and museums, too. Butterflies are very visually appealing and books on them are brightly coloured and they attract a lot of interest. Buprespid (jewel) beetles have fantastic metallic bodies and I could watch leaf-cutter ants for hours.
A copy of the flower fairies books might be a good start, the illustrations have a definite insect feel to them (and I wish I could paint like that. I still kick myself for taking physics over art at school). I think that the more you get used to seeing insects, the easier it is to handle them. I had insect books, stamps and Brooke Bond tea cards (remember them?) as a child along with other boys stuff- maybe there need to be more insect themed computer games.
JenaiMarrHePlaysGuitar: The enormous, prehistoric-style, extraordinarily noisy dragonflies we usually get at home are very cool. The first time one flew into the sitting room it scared the bejesus out of me. I've not seen any this year though so I wondered if that was a national trend.
Matthew: I will gladly talk about monstrous dragonflies all day long, they are far more interesting than wasps. This, and the paper it refers to, is one of my favourite research projects in entomology:
It includes this brilliant quote: "Dragonflies in the modern habitat grew normally, with wingspans of about 3.5", while the hyperoxic chamber spawned dragonflies with 15% larger bodies and 4" wingspans." Four-inch dragonfly breeding! Science doesn't get any better than that! Wet spring times usually mean more dragonflies. Dragonfly larvae are aquatic and carnivorous and feed on mosquito larvae, amongst other things. Wet spring times mean more mosquito larvae and more dragonflies in the following summer.
Fluffyanimal: Is there any effective insect repellent against horseflies, having been bitten through my shirt by one not long ago?
Matthew: Interestingly, horse owners add wine vinegar to horses feed to deter horseflies. Strong cider may have a similar effect, but I'd need to field test it, extensively, before I recommended it.
Tabanid flies, which include horse flies, are pretty unpleasant. The females have two-bladed mouthparts that cut through skin causing an open wound from which they lap blood. DEET products are effective, to a point, against these sorts of flies.
Slubberdegullion: Can I treat some of my children's leggings and socks with a permethrin spray? (I've bought it to treat a mossie net with.) Is it safe to use on clothes or will socks tucked into trousers suffice for forest walks?
Matthew: I wouldn't recommend applying permethrin to clothing worn next to the skin; some people have strong reactions to synthetic pyrethroids. Wear loose clothing and make sure you are well covered up below the knees where ticks are most likely to bite.
GreatGooglyMoogly: What is the best way to remove a tick?
Matthew: A good pair of tweezers and a steady hand. As long as nobody panics and starts thrashing wildly you can remove a tick by grasping it as close to the skin as possible and applying steady pressure until it releases.
Mybrainsthinkingfuckyou: I'd heard that the army used Avon's So Soft range (as opposed to Avon repellent); so I bought some for my step-dad, but it had no discernible effect as a deterrent. Is it just an urban myth?
Matthew: As with a lot of these stories, there is some truth to it but it doesn't seem to be as black and white as it first appears. Avon themselves make no claims for insect repellence in that range but point out, interestingly, that many formulations contain citronella, described as unnamed perfume, for formulation protection.
However, items in that range have been laboratory tested and show some limited effect in repelling mosquitoes, which is a very interesting read as it cites research that has shown that men are more attractive to some mosquitoes than women, larger folk are more attractive than smaller and that some fragrances and soaps might attract mosquitoes. It also suggests that people become less attractive to mosquitoes as they age. It includes a fairly objective safety review of DEET products, too.
Belgianbun: Is it me, or are there more and more people needing antibiotics for insect bites?
Matthew: The more you scratch at bites, the more likely it is that you will get a secondary bacterial infection. Scratching bites or stings is about the worst thing you could do to them.
Bibbit: Please give me your top tips for getting rid of hide beetles. I have already had the council in to spray but they survived.
Matthew: You need to work out what it is they are feeding on and either remove it or isolate it. Hide beetles feed on skins, hides and meats, including dead rats, pet foods and taxidermy and museum specimens. These insects are not difficult to kill with commercial insecticides, but you have to know where to apply it. Finding what they feeding on and removing it is a critical first step.
Curlywurl: How harmful are fleas to humans in the UK? Is there anything nasty they tend to pass on in this country? We have treated our dogs with Frontline Spot on but are still finding a few fleas on the lounge carpet. I don't really want to use loads of chemicals on the carpet where our baby rolls round all day.
The fleas we find are quite drunk looking or dead already so I assume that's the effect of the treatment we used on the dogs. Are we best just waiting a while or is there something safe we can use on the carpet?
Matthew: Theoretically, a dog or cat flea can pass along the infective stage of a dog or cat tapeworm if the flea is ingested. Unfortunately, from what you've described, having a baby on the floor with a lot of immobile fleas seems to increase the risk.
Topical application of Fipronil to cats and dogs is a very effective way to kill fleas - certainly a great deal safer and more effective than spraying my cat with aerosol Dicholvos as I routinely tried to do years ago. A good 'animal type' vacuum cleaner would seem to be a prudent measure. Vacuum after treating your dogs and remember to empty the cylinder or bag afterwards to stop the fleas jumping back out again.
Waltons: I fear that I have either a mouse or cockroaches in my house, because I am finding small black droppings. A mouse wouldn't be a surprise - they have got in before and we are in a rural area, but I would be feeling really ill if it were to be cockroaches.
Matthew: Cockroach and mouse droppings are different in scale. Cockroaches leave 'spots' on surfaces or very fine granular droppings (depending on the cockroach); whereas mouse droppings are 3-4mm long, black/brown and pointed at both ends.
VenetiaLanyon: Why do some people attract midges more than others?
DoodleAlley: Why do I get bitten so much more than my husband or son? DH claims I am his best anti-bite solution.
Matthew: Researchers have spent quite a bit of time looking at what attracts mosquitoes in order to entice them to traps. What they have found is that the cocktail of chemicals emitted by some people are very attractive to mosquitoes, whilst others emit cocktails that are much less attractive.
Lactic acid and human sweat are both known to attract mosquitoes, along with a few other chemicals including things like some floral soaps.
Again, I'm not an immunologist; different people react to antigens in mosquito saliva in different ways. All I can suggest is that you seek medical advice if you have a strong reaction to an insect bite, bearing in mind that not all insects will provoke the same response from your immune system.
PrettyCandles: Why am I so beloved by stinging insects? For example, when we camp in summer, my husband and I often shower with the children in the evening, and then sit outside in the dusk while they fall asleep in the tent. We will both be clean, not sweaty, and have washed using the same toiletries. Yet I am bitten every night, and he is left untouched. To add insult to injury, my bites swell up into incredibly itchy hard white lumps (unless I take antihistamines), whereas his are just a bit red and vaguely itchy, and heal within a couple of days.
LeninGrad: I think we had one bed bug once, just the one thankfully, but it lived for quite a while and bit my son's legs eight to 10 times at a time about six times over as many months. Does that sound likely? I was about to chuck everything, eventually I sprayed enough chemicals and sealed off enough gaps to kill it.
Interestingly, I was in the same sleeping space as him and didn't get bitten at all but my partner did - how come? Bad timing or something else?
Matthew: I'm not an immunologist or a dermatologist, so I can only give a generalised answer to why some people react differently to different insect bites. Some people can have or develop hypersensitivity to insect bites to varying degrees. The type of reaction you get from a bite can depend on previous exposure. Repeated bites might lead to an allergic reaction, shown as a skin weal. For example, people bitten by bed bugs can show progressive sensitivity to repeated bites. Common reactions to bed bugs bites are:
- No reaction at all
- An immediate weal formed that lasts a few days
- A delayed reaction with a weal formed many days after the event
One answer to the question of why some people are bitten more than others might be that everyone is being bitten with the same frequency; it's just the reaction to the bites that are different.