Black-legged ticks (Ixodes scapularis) are indisputibly blood-sucking, disease-transmitting parasites, but they are also marvels of mechanical engineering (in a non-teleological, Darwinian sense, of course).

The critter on the left is a female black-legged tick (also called a deer tick) in her fasting state, and on the right is another individual after completing a meal of Musti’s blood.  For scale, the unfed female is about the size of a sesame seed, growing to the size of a coffee bean after a full meal.