Fauna Flora Mutualism

Let $x$ be the number of insects and $y$ be the number of plants.

STRATEGY:

Logic: For every $1$ plant, there are corresponding $x$ insects on it.

So, simply multiply $x$ insects to the number of $y$ plants, then find the sum of those products.

$(5\times1)+(4\times20)+(6\times30)=5+80+180=\boxed{265}$ insects.