Hi Jaap Kleijkamp , this question has already been answered here:

https://www.researchgate.net/post/which_method_is_good_for_insect_DNA_isolation

Best of luck

I agree with Evan S Haworth that there are excellent answers already on site. I would just add that column purifications can often be improved ( greater yield) with the use of hot elution buffer at the final step and also washing the dna off the column twice not just the once. If after that any concentration of the dna is needed then add a co precipitant such as linear acrylamide or glycogen to make sure that all of the dna is precipitated

Also, thorough sample grinding and being careful to not overload the column with sample (there is such a thing as TOO MUCH starting material) will help a lot. If your insects are normally fatty, then I'd use legs or similar to avoid gunking up the column with lipids.