I had to look it up and found a pretty good web site about them:
http://entnemdept.ufl.edu/creatures/urba...eetles.htm
Here's the highlights:
False blister beetles, sometimes known also as pollen feeding beetles, are unique in that adults of all the approximately 1,000 species in the world are obligate pollen feeders. They obtain their common name because many species cause blisters when pinched or squashed against the skin. Being pollen feeders, they are often common on flowers. They are also attracted to lights, and their numbers can be vast at night, especially on the Florida Keys. Oxycopis mcdonaldi (Arnett) causes skin blistering and makes itself a nuisance at resort areas where the beetles are attracted by night lights around swimming pools, tennis courts, and open air restaurants. Yet another species, Nacerdes melanura (L.), the "wharf borer," is common around wood pilings where its larvae bore into and weaken the wood of docks and adjacent buildings.
Blistering of human skin is caused by the oozing of cantharidin, the same chemical found in blister beetles (Meloidae), from which the drug known commonly as "Spanish fly" is extracted. An early report of this syndrome is one by Herms (1925) who described the blisters as follows: "..if, for example, [the beetle] is slapped when crawling on the forearm ... [or] rather lightly brushed away, ... the following day a large blister appeared, measuring about three-quarters of an inch in length by one-quarter inch in breadth, considerably elevated and filled with clear liquid. I opened the blister and applied iodine. The blister did not cause any appreciable pain." Vaurie (1951) reported blistering from Oedemeridae attracted to coconut palms, Sabal palmetto, and black mangrove blossoms. She received many blisters which were painful and took weeks to heal. The susceptibility to blistering varies considerably. Some people are extremely susceptible, while on the other hand, the author, who has collected these beetles for 40 years, has never been blistered!
In Japan, the insects are known as "poisonous beetles" (Kurosa 1977). There, 47 species occur, and tests of all available species (21) show they contain cantharidin. It is likely that all species produce this substance.
