In Texas, we have mosquitos and fleas year round so all my girls get the Revolution which covers both. We like it because it is dosed by weight and with Princess being 3 lbs., i don't want to give her too much so she is on the puppy dosage. Mine have never had a reacation to the application and i like that i can bathe them soon afterwards. Although i usually bathe them right before application, I don't bathe them after application for about a week just to make sure.
if you pull up heartworms on google, there is a map that tell you if you area is prone to heartworms/mosquitoes.
KNOW Heartworms | Incidence Map
or
Heartworm Incident Map
Here are some maps of the known incidents. Texas is pretty heavy as well as all the states along the Mississippi River and coast line. Mosquitos breed in water so if you live near any water, you probably have them unless it is really cold where you live.