There are a number of obstacle that insecticides used indoors due to adopted new behavior to avoid insecticide, including changes in biting phenology and the frequency of endophagy. All anopheline vector species predominantly feed at night. One of the consequences of large-scale indoor insecticide use is that to change behavioral pattern with increased proportion of human attack during evening or morning while they are outdoors or before sleeping. Following IRS used widely in isolation in the Garki project in northern Nigeria due to outdoor resting behavior malaria parasite rates failed to reduce substantially (Molineaux and Gramiccia, 1980).
In a different geographical area Anopheles arabiensis populations show a wide range of peak biting times (Fontenille et al., 1997, Lemasson et al., 1997, Yohannes et al., 2005, Yohannes and Boelee, 2012) with some of this variation being described by season ( HYPERLINK l “_2szc72q” h Tirados et al., 2006 ). However, one possible explanation for the switching peak biting times was due to the historical use of insecticides. Most interventions against this vector have involved IRS, which kills indoor resting mosquitoes but not outdoor resting mosquitoes. outdoor feeding species that are highly anthropophagic need to feed early in the evening when humans are readily available outdoors. DDT has been used for IRS in Ethiopia for the last 40 years and there is some evidence in this country for increased exophily (Biscoe et al., 2005, Yohannes et al., 2005, Yohannes and Boelee, 2012, Tirados et al., 2006)