How would you identify a grub to species?

• A. By color alone
• B. By wing pattern
• C. By looking at the raster pattern with a 10x or 20x hand lens
• D. By size alone

Answer: (C)

Grub species identification rests on a stable morphological feature that can be seen clearly with magnification. Colors and overall size can vary a lot with age, diet, and environment, so they aren’t reliable for telling species apart. The most reliable diagnostic trait for many scarab grub species is the raster pattern—the arrangement of spines and bristles on the last abdominal segment. Under a 10x to 20x hand lens, this pattern becomes visible and distinctive, allowing you to distinguish species by comparing what you see to reference keys or drawings. Grubs do not have wings, so wing patterns aren’t a factor, and relying on color or size alone can mislead because different instars look quite different. Focusing on the raster pattern under magnification provides the most accurate species identification.