Where the name originates
"Formica" is a Latin word, which means ant, while "philia" originates in Greek, and it means friendship or love. Therefore formicophilia literally means "antlove." As the attraction to insects is usually not limited to just ants, the term entomophilia is also used, to cover a wider, more general meaning. The expression means insect love. While in most cases it is a more accurate description, formicophilia is the more often used expression.
So what is it?
This "philia" is a type of zoophilia and means the desire of having insects crawling on one’s skin, or causing distress for other people by insects. In certain cases this desire is extended to include worms, snails, or frogs. Those who have this paraphilia either enjoy the tickling sensation the legs of the insects create, the biting feeling, or the distress of others. Usually the genitals, perianal areas, and the nipples are the center of the desire, but it is not necessarily so. Other body parts can be in the focus too, especially if the person has other type of fetishes too (like foot fetish).
The most common practice among the formicophil is to allow insects crawling all over their skin. Some of them would smear honey on their bodies and allow the bugs to feed from them. Some of them would place the insects in different orifices, finding the sensation of the insects trying to escape pleasurable. In the case of liking worms, they are often stuffed into underwear or pantyhose, which is held over the desired area(s).
Dr. Brenda Love reported a case of how bees can be incorporated to the fetish. The patient watched his grandparents relieving joint aches by using bee stings, learning about the properties of the venom. He also had an accident of getting his genitals stung, and found it to increase the intensity of his orgasms. Also he found the sting to be more like a mosquito bite, unlike on other body areas. That is how he developed his method. Catching two bees, closing them in a jar and shaking it to make them dizzy, grabbing them by their wings and placing them on the two sides of his penis, and pushing them to encourage the sting. The circumference of his penis increased from 6.5 to 9.5 inches.
Another type of formicophilia is the "crush fetish," finding sexual pleasure in watching bugs and worms being crushed and walked upon. Preferences could be barefoot, sandals or heels. Usually it also involves the disgust or fear of the woman.
Where it originates
Doctors and psychologists either disagree, or do not claim to know the origin of this paraphilia. They only agree that it is most likely the result of strong emotional influence received in childhood or adolescence. Sexual statistics show that the most common occurrence of it is in developing countries, probably because it is more common to find homes with insect infestations.
There are also cultural variations from Japan, the so called Genki Genki, which features women having intercourse with different creatures. Most of those are sea-animals, but insects can be found here and there.