I had the exact same problem with the OP, and had the exact same solution at first. From my interpretation of the rules, there is nothing that says the solution needs to have the minimum number of boxes. It says boxes have to be made with the least number of sides, which would be 4. This leads to an infinite number of boxes, as long as each has 4 sides and is spacious enough to contain the bugs within.
The rules also do not say anything about boxes being unable to contain more than one type of bug. It says the SAME bug CAN be in the same box, but it does not say that DIFFERENT bugs CANNOT be in the same box. So theoretically, you could draw one big box along the outermost border and solve every possible puzzle this way, since multiple bugs in the same box, no matter how big, is not prohibited.
I know I sound like I'm being technical, but the rules need to be sufficient in order to rule out any unintended solution.