Partial exophily of Anopheles gambiae species B in the Khashm Elgirba area in eastern Sudan.

Many Anopheles gambiae were found resting outdoors in an area that had been sprayed with DDT, the numbers being particularly large 4 months after the first annual spraying cycle. A high proportion of the resting females had consumed a blood meal. Window-trap studies showed that a marked exodus from sprayed huts occurred in the morning. It is concluded that the outside resting of An. gambiae is either a natural habit or the result of the irritant action of DDT. This behaviour of the vector is regarded as one of the factors responsible for the marked increase of malaria in the area.