The essence of science is making observations and then constructing models that explain those observations. Once your model is established you then test it (this is the “experiment” part of the scientific process) and then re-write it or throw it out, or, if it seems to stand up to your test, very tentatively accept it. Sometimes this process happens in a blur of interconnected events or mental leaps, and sometimes it happens slowly and methodically over many months or years.
I made an observation the other day as I was cleaning up our deck in anticipation of company coming over. On the deck railing, under a piece of indoor-outdoor carpet were several hundred ants. When I moved the carpet the ants began to scurry about grabbing up their larvae, and rushing into safe spots down in between the spaces of the deck timbers. I used a broom to sweep the lingering ants off of the railing and send them down into the flowerbed below (although if company wasn’t coming over I probably would have just watched them for a while). Several ants, I think, were damaged in the sweeping, but most tumbled down into the plants and, I am sure, set up their colony in a more appropriate spot. I set the broom down and noticed a few minutes later that both of my cats were rubbing and rolling on the broom like it was the finest cat-intoxicant they had ever encountered.
Observation: cats like whatever chemical agitated and/or smashed ants give off.
Ants (and a number of other hymenopterans, too) use formic acid as a defensive secretion. In fact, all ant species belong to a taxonomic family called “Formicidae,” a name that emphasizes the ubiquity and abundance of formic acid in their tissues. Formic acid is the simplest of all organic acids. It consists of a carboxyl (the functional, “acid” group made up of one carbon atom, two oxygen atoms, and a single hydrogen atom) onto which one, additional hydrogen is bonded. Since all organic acids contain carboxyls, and since hydrogens are as simple and as small an additional atom as there is, you can’t make a more stripped down organic acid molecule than formic acid!
So, do cats go crazy for formic acid? I didn’t have a bottle of formic acid to play with so I did the next best thing: I went to the Internet. There were a couple of people who had previously observed the cat/ant behavior who did go out and do the actual challenge to this explanatory model. The result: Cats aren’t interested in formic acid at all. The model is rejected.
An interesting side note that I came across, though, concerned animals that eat lots of ants. Picture the anteater. It consumes many thousands of ants a day and thus ingests huge quantities of formic acid. It turns out that an anteater’s stomach then uses these formic acid molecules as a metabolic replacement for the hydrochloric acid that is made (with some considerable metabolic expense and physiological wear and tear) in the stomachs of most vertebrates (even people!). Stomach acids primarily function to sterilize food and thus keep bacteria and other potential pathogens from entering the small intestine. Anteaters get this function for “free” as a tie-in to their ant-rich diet! There are birds that eat a lot of ants, too. I wonder if their stomachs make less hydrochloric acid that other, non-ant eating birds?
But I digress: ants it turns out have a lot more chemicals in their bodies than formic acid, and someone has actually analyzed the composition of an ant and especially squashed ant juices (and published their results on the Internet!). Major components of these squashed ant concoctions are fatty acids (molecules that are long, relatively straight carbon chains that have a carboxyl group at one end of the molecule). One of the very abundant fatty acids in ants is oleic acid (an 18 carbon long fatty acid with one point of unsaturation in the middle of its carbon chain). Oleic acid is a well known insect pheromone and also makes up most of the fatty acids in the triglycerides of olive oil! It is also thought to be a major secretory product of a cat’s “facial glands” (the glands that secrete a soothing pheromone when a cat rubs his or her face on an object or individual that he or she finds pleasant or agreeable). Apparently the blast of oleic acid in the ant “juice” said “home, wonderful home” to any cat that came in contact with it.
Pretty straight forward, but it is the just the start of my Internet driven exploration of formic acid.
I found out that while formic acid can be toxic to humans (or any other life form) in large concentrations, it is also regularly ingested in trace quantities in food and is also synthesized metabolically as the least of three evils in a triple array of toxic chemicals. When we eat fresh fruits or vegetables some of the carbon molecules in that food item have undergone fermentation. The products of the fermentation could be organic acids or aldehydes and ketones, but they can also be alcohols like ethanol (the desired, two carbon long alcohol in beverage fermentations) or methanol (the very toxic, one carbon long “wood alcohol”). So when you eat ripe fruit (or ripe vegetables) you ingest a small amount of the very toxic methanol! There are enzymes in your liver that change these trace concentrations of the methanol into the slightly less toxic but potentially cancer causing molecule called formaldehyde. Fortunately, there is also a liver enzyme that quickly changes the formaldehyde into formic acid which because of its great water solubility is rapidly excreted from the body by the kidneys.
Any foods that are rich in methyl groups have the chance of generating methanol during digestion, and these absorbed methanols are dealt with via the formadehyde/formic acid excretion pathway.
Which gets us to the last item in the title of this essay: aspartame. Aspartame is a synthetic sweetener that is two hundred times “more sweet” than sucrose. It is made up of two amino acids (aspartic acid and phenylalanine) that are held together with a peptide bond. Near the peptide bond, though, on the phenylalanine is an added methyl group. The whole package (a “methylated dipeptide”) stimulates sweet receptors in the taste buds like crazy and can make a food or beverage taste incredibly sugary without having any sugar (or any of sugar’s calories!). There are two extreme opinions about aspartame: it is either absolutely safe and an efficient way to avoid sugar in your diet, or it is the most insidiously damaging chemical additive in our food supply.
Most research studies have resulted in findings that lean well toward the safe side of aspartame’s impacts, but we should not ignore that other side of the argument. While it has not been shown that adding these two very common amino acids to foods and beverages does anything to disrupt amino acid metabolism (and brain neurotransmitter chemistry), that extra methyl group without question generates methanol which then forms formaldehyde and formic acid in anyone ingesting aspartame. Let’s leave this as some people may be extremely sensitive to these chemicals and that no one wants methanol or formaldehyde or formic acid percolating through their tissues!
So, watching cats go crazy over a broom that has ant juice on it got us all the way to aspartame with a side trip into anteater digestive physiology. Sounds like enough for today!