It's heartwarming that when people see articles about bizarre feeding or sexual practices in invertebrates, they instantly think of me and send me a PDF (thanks, Kevin Bolding!) Here's a spider, Evarcha culicivora, with a happy appetite—it eats mosquitos. We Minnesotans would be pleased with that.

However, it prefers to snack on mosquitos that have already had a blood meal. It likes its prey to load up on our blood first, and then it catches the engorged mosquito and gets a tasty dollop of red-blooded chordate juice with the crunchy insect. We're like ketchup to these guys!

Spiders do not feed directly on vertebrate blood, but a small East African jumping spider (Salticidae), Evarcha culicivora, feeds indi- rectly on vertebrate blood by choosing as preferred prey female mosquitoes that have had recent blood meals. Experiments show that this spider can identify its preferred prey by sight alone and by odor alone. When presented with two types of size-matched motionless lures, E. culicivora consistently chose blood-fed female mosquitoes in preference to nonmosquito prey, male mosquitoes, and sugar-fed female mosquitoes (i.e., females that had not been feeding on blood). When the choice was between mosquitoes of different sizes (both blood- or both sugar-fed), small juveniles chose the smaller prey, whereas adults and larger juveniles chose the larger prey. However, preference for blood took precedence over preference for size (i.e., to get a blood meal, small individuals took prey that were larger than the preferred size, and larger individuals took prey that were smaller than the preferred size). When presented with odor from two prey types, E. culicivora approached the odor from blood-fed female mosquitoes signifi- cantly more often the odor of the prey that were not carrying blood.

More power to the clever arachnid, I guess, but I'm just not used to thinking of myself as a condiment.

Jackson RR, Nelson XJ, Sune GO (2005) A spider that feeds indirectly on vertebrate blood by choosing female mosquitoes as prey. Proc Natl Acad Sci U S A. 102(42):15155-60.