There is nothing like picking a raspberry and finding a small beetle in the “cup.” (Actually there is something els,e and that is the crunching sound as you eat the beetle in the cup of the raspberry!)
This insect is the picnic beetle, a small beetle that loves fermenting fruit (and potato salad at picnics). Raspberries are one of their favorites. The beetle can quickly ruin a ripe raspberry as they burrow around inside the fruit. There is little that can be done to stop these insects. You cannot spray since you are spraying fruit you are about to eat. I generally see picnic beetles become a problem when you are not picking the fruit often enough – pick all the fruit as it ripens, daily or twice a day if needed. The beetles are attracted to over-ripe fruit and by picking the fruit as it ripens you are eliminating the attractant.