Common Geranium-bronze Cacyreus marshalli

Don't let the modest size fool you—this geranium specialist has the power to devastate garden plants across multiple continents. Its common name references its extraordinarily specific taste: it nearly exclusively feeds on geranium and pelargonium plants. Being so specialized on a single plant family means it can reproduce explosively when those host plants are abundant, which is exactly what happens when pelargoniums grace gardens worldwide. This extreme host specificity makes it a fascinating case study in coevolution between insects and plants—and a cautionary tale for gardeners everywhere.