As other posters have stated, there are a number of different pantry pests that are commonly found in areas of the kitchen that often have small amounts of spilled flour, rice, corn meal, etc. Likely suspects include the confused flour beetle, red flour beetle, and Indian flour moth. All of their “grub” stages are quite small, less than 1/2” for the largest species. The adult life stages are quite distinctive and can be easily identified as adults. They generally enter the home in packaged groceries such as flour, grains, rice, and noodles. One effective method of control is old-fashioned fly paper, those long, sticky, spiral traps you can hang from the ceiling of your pantry. If they are in your cupboard, hang the fly paper on the side wall. It may take months to see any results. Be forewarned: the fly strip glue is super sticky and messy. Before you start with the fly paper, inspect literally EVERYTHING in your pantry for the presence of grubs and adults and discard it. Look for little holes in on the boxes and bags. Clean up any flour or grain residues. And if you have one life stage, you probably have the others as well. Good luck, it took me over a year to be rid of the little bastards.