Here is a general answer to the question:
Only female mosquitoes take blood meals. Males never do. Males eat
plant materials such as nectar. Females do as well. Females are
supposed to take blood meals only at a certain point in their lifecycle,
when they are a few days away from laying their eggs (and the blood
provides iron for the eggs.)
Now I'd like to ask a related question. Does anyone know exactly
what plant materials each of the Anopheline vectors eat (i.e., A.
gambiae)? I should think this would be important and it might provide
clues for: 1) trapping mosquitoes and 2) site-specific insecticide
application. I was told by a botanist once that the mosquito proboscis
is adapted to sucking from xylem and phloem (as well as capillaries).