Flowermix Oak Processionary Caterpillar. Composed of 90% native species and is a combination of annual, biennial and perennial species. The advantage of using it is immediately apparent in the first year because this nicely composed mixture is a source of nectar, pollen, and seeds which are attractive to spiders, parasitic wasps, and birds, the natural enemies of the oak processionary caterpillar. Make the soil where the caterpillars are located free of weeds and then sow and rake in this seed mixture.