Malacosoma castrense, the ground lackey, is a moth of the family Lasiocampidae. It is a tent caterpillar found in Europe. The length of the forewings is 13–16 mm for males and 17–21 mm for females. The moth flies from June to August, depending on the location. The caterpillars feed on various shrubs and herbaceous plants such as heather, cypress spurge, and Lotus species.