The teasel, Dipsacus fullonum is known to catch invertebrates in its water filled leaf bases, but experimental testing of reproductive benefits of this have been lacking. We report the effects of insect supplementation/removal and water removal during spring/summer on Dipsacus in two field populations. There were no significant treatment effects on biomass, but addition of dead dipteran larvae to leaf bases caused a 30% increase in seed set and the seed mass:biomass ratio. This study provides the first empirical evidence for reproductive benefit from carnivory in Dipsacus fullonum.