From the ever-fascinating Stu:
(apparently he's working on bringing them to North America)
BETTER THAN SILICON
Young girls from East Africa (mostly Ethiopia, Tanzania, and Uganda) use whirligig beetles (Gyrinidae) and predaceous diving beetles (Dytiscidae) to stimulate breast growth. The girls will hold the live beetles up to their nipples, where the beetles bite in a defensive reaction. This practice was most widespread in girls in rural communities that were from 7 to 12 years of age.
The bite of the beetles is described as a stabbing, burning pain that eases after 30 to 60 minutes. Two to three days after the bite the breast will be slightly swollen. Most of the girls also reported that their breasts grew bigger in the 6-12 months following the treatment. This bit of ethnobiological knowledge is unique in that it is almost entirely passed on amongst the young girls and not from mother to daughter as would be more common for other traditional knowledge.
In practice in Uganda is slightly different than in Ethiopia and Tanzania. It was common in a bit older girls, from 14 to 15, if they found their breast development to be unsatisfactory, and they would be told about it by their grandma instead of their peers. Also, antlion larvae would sometimes be used instead of the beetles.
Similar practices have also been recorded in Zimbabwe, Kenya, and Congo, although it isn't as widespread there.
Water beetles in general produce a wide variety of compounds that are antibacterial and antifungal, as well as often acting as an anaesthetic, narcotic, or toxin to vertebrates. Gyrinids produce a variety of unique norsesquiterpenes in their pygidial glands. These compounds are structurally related to nepetalactone, the active component of catnip. Dytiscids have prothoracic glands that secrete large quantities of a great variety of steroids. Some of the steroids that have been isolated are: progesterone, androsterone, deoxycorticosterone, testosterone, estradiol, cholesterol, and mirasorvone.
Reference:
Kutalek, R., and A. Kassa. 2005. The use of gyrinids and dyctiscids for stimulating breast growth in East Africa. Journal of Ethnobiology 25(1): 115-128.