Pin  and  thrum  flower  types reduce self-fertilization. Some species
   produce  two  types of flowers: pins, which have long styles and short
   stamens,  and  thrums,  which  have  short styles and long stamens. An
   insect  foraging for nectar would collect pollen on different parts of
   its  body;  pin  pollen  would be deposited on thrum stigmas, and vice
   versa.