Nootkatone.

Grapefruit, courtesy Wikipedia.

So,

It is summer in the northern hemisphere.  There is much fun to be had in the sun, vacations and adventure abound.  Unfortunately, with summer comes mosquitoes, and various other biting insects.  The worst part about such pests is that the only 100% solution is to completely cover oneself, which seems impractical and needlessly warm in such a season.

I have long pondered how to deal with such problems.  In earlier years, I investigated how to breed dragonflies.  I had seen them hunt the pests while camping, and was intrigued.  Regrettably, dragonflies breed in standing water, as do mosquitoes.  I have also considered constructing a "bat box", a box in which bats may rest during daylight hours.  In my search through unofficial literature, I found that one can fairly easily house 300 bats in a larger box.  As an interesting aside, in Canada it is necessary for one broad side of the house to face south, and to paint the box black so that the bats will be warm during the day.  I had no idea this would be a concern in weather that I consider stifling.  I also discovered that pests may be deterred by the sound of the bats (imperceptible to us, but a loud alarm to biting insects), which could also provide relief.  For a second digression, I would be curious as to whether or not the presence of a bat house would discourage nesting within human homes.  I know one family who seems plagued by bats in August.  Would a nearby bat box provide an easier home, or draw more bats to the site, and thus the family home?  Details or case studies would be appreciated.

As a final digression on the topic of bats, let us consider ammonia.  Bat feces are rich in the stuff, that which humans use for both explosives and fertiliser (especially for hungry crops like corn).  Brazil (I think) was a world power in the production of ammonia due to its large bat population.  This was, of course, before the Haber process was developed.  This allowed humanity as a whole to produce ammonia from nitrogen and hydrogen gases, and also allowed the Germans to produce explosives in the absence of mined ammonia during The Great War, or WWI.  For the record, there are no evil chemicals, only humans who use them poorly or without due respect.

Digressions aside, whilst bat boxes seem like a good idea to reduce the pest population, I am certain that I would still be bitten throughout the course of the summer.  Currently, the best solution is to use various products one burns to repel mosquitoes, or to use DEET to hide oneself from the pests.  This is a bother to me, that DEET is called a "repellant", but does nothing to repel insects, only hide us from them.

"Now, see here!" I assume you are demanding by this point, brows furrowed over monocles, Brandy angrily swirled.  "Why on Earth did you start this article with a picture of a grapefruit?"  An excellent question, my non-spambot friends.  It would seem that there do exist chemicals which will repel ticks, mosquitoes, biting flies, and all your most hated pests.  One is called nootkatone, and it will repel these insects.  The best part?  It is harmless to us, humans are not affected by the molecule.  The downside?  You will smell like grapefruit (if you dislike that sort of thing).  This is, really, the worst effect of a nootkatone repellent.  It is part of the aroma of a grapefruit, and is added to a beverage known as "Squirt", which I have never consumed.  Grapefruit, so you know, does not contain high enough concentrations of nootkatone to deter the pests itself.  Spreading grapefruit juice on yourself will only make you sticky and dissatisfied.

Nootkatone, courtesy Wikipedia.

The effect of nootkatone on a pest is rather dramatic.  The molecule attacks the nervous system and by some mechanism which I do not understand, causes severe over-stimulation.  The insect will shake itself to death.  The bugs are aware of this, and are deterred by the scent of it.  Whereas an arm covered in DEET will be ignored by mosquitoes, the same arm covered in a 2% solution of nootkatone will repel mosquitoes.  Should the insect pursue your flesh anyway, it will die.

For now, nootkatone is considered "prohibitively expensive" to use in commercial repellents.  Actual repellents, what a concept!  At roughly $4000/kg, there are far cheaper alternatives.  Nootkatol, the alcohol equivalent to nootkatone's aldehyde, has been shown to demonstrate similar effects, and may be much cheaper to manufacture.  Hopefully once organic chemists work their magic, we may have a way to manufacture the nootkat- family of molecules cheaply and efficiently.  I shall continue to hope anyway.  I hate being bitten.

NM