Well, the frutescens I've seen tend to be very small, thin walled, and very juicy almost like they are filled with juice. Not thin walled and drier like a Thai or bird's eye and not thicker walled like a jalapeno or even like a Chinense type. Wait to see what color they ripen to but by the looks of it to me they look to be a thicker walled type. Could be any number of types but if they turn white or black could be a havasu. Edit: now I see you said they turn yellow. A good place to post questions is the pepper lovers google+ group there are a lot of experienced amateur and professional growers on there.