Why do ticks swell so much after feeding?

Ticks are adapted to feeding slowly over many hours or days, and their bodies can dramatically expand while they gorge on blood. The tick cuticle is flexible enough to stretch, and the digestive tract can handle a meal far larger than the unfed body. This feeding strategy helps ticks obtain enough nutrients to progress through their life stages and reproduce. Unfortunately, ticks are also important disease vectors, transmitting illnesses such as Lyme disease and Rocky Mountain spotted fever in different regions. Their swollen appearance is a direct result of a specialized parasitic life style.