Which insects are known to cause severe itching and have a life cycle of 18 days?

The insects that are well-known for causing severe itching and having a life cycle of 18 days are lice. Lice are parasitic insects that infest the hair and scalp, as well as other areas on the body, depending on the specific type of louse. The life cycle of lice includes three stages: the egg (nit), the nymph, and the adult. The entire process from egg to adult can take around 7 to 10 days, but the lifespan of an adult louse is typically about 3 to 4 weeks. Therefore, the combination of reproduction and growth can often lead to an overall life cycle that can average out to a couple of weeks, around the time frame mentioned.

Severe itching occurs as a result of an allergic reaction to the saliva of the lice, making them particularly notorious for causing discomfort. This symptom is one of the most recognizable signs of a lice infestation.

Other options may involve insects that can cause itching, such as mites or ticks, but they do not fit the specifics of causing severe itching in the same manner or have a life cycle closely tied to the 18-day duration described.