Malaria remains a major public health threat in sub-Saharan Africa as the most efficient vector, Anopheles
gambiae s.l, continues to adapt to humans  and is a complex of sibling species taxa, thus resulting in a high vectorial capacity. The complex consists of seven species that vary in their ability to transmit malaria . Currently known sibling species within the complex include An. gambiae s.s. Anopheles arabiensis, Anopheles melas, Anopheles merus, Anopheles quadrianulantus (A and B) and Anopheles bwambae. Their distribution is associated with particular climatic zones and degrees of aridity [3, 4]. In some areas of sub-Saharan Africa, where mosquitoes of the Anopheles
gambiae complex are the most important vectors of malaria, individuals may receive up to 800 infective bites per person per year (ib/p/y) . However, in other areas of Africa, An. gambiae is found together with Anopheles
funestus and both vectors compete in terms of their importance as malaria vectors 
The An. funestus group consists of seven to ten morphologically difficult to distinguish sibling species. Among the group, An. funestus s.s is the most anthropophilic and efficient vector. More recently, chromosomal analysis in sympatric populations of this vector has led to provisional names of chromosomal forms such as Folonzo and Kiribina . This vector has been extensively described in Navrongo in northern Ghana and in neighbouring Burkina Faso, where it is an efficient malaria vector [7, 8].
The entomological inoculation rate (EIR) estimates the level of exposure of an individual to malaria-infected mosquitoes and it is the most favoured measure of assessing malaria endemicity and transmission intensity [5, 9]. There is a strong correlation between EIR and the prevalence of malaria in a population and, as such, it has become the most accurate measure for estimating transmission. Estimated EIR in the northern part of Ghana (Navrongo), where there is an irrigation programme, is 643 infective bites per person per year (ib/p/y) . In the southern forest (Dodowa) and coastal areas (Prampram) of Ghana, estimated EIRs were 21.9 and 3.65 respectively . There is, however, little information about the intensity of malaria transmission in the middle belt of Ghana required for the design of effective vector control strategies.
s.s. has been shown by the extent of chromosomal inversion polymorphism and, more recently, by divergence at the molecular level to consist of two molecular forms M and S . In addition, five chromosomal forms named under a non-linean nomenclature as Forest, Savanna, Mopti, Bamako and Bissau have been identified . This vector has been extensively implicated in malaria transmission in West Africa and Ghana in particular . Climate affects the distribution of both chromosomal and molecular forms .
Insecticide resistance of the type kdr (knock down resistance), which influences response to pyrethroids and DDT, has been detected in many West African populations of An. gambiae s.s . Mutations in the kdr target site, voltage gated sodium channel, have been observed in West Africa An. gambiae species . In most investigated West Africa countries, the kdr allele was detected in S populations and absent in all sympatric M populations, thus supporting the hypothesis of reduction of gene flow between them . Data on An.gambiae s.s indicate introgression in the S and M molecular forms in Benin and countries to the east . The kdr allele is observed in the M form in Benin , but mainly in the S form in most West African countries such as Ivory Coast and Ghana, Nigeria, Mali and Burkina Faso [1, 10, 12, 15, 16]. Though at a lower frequency, kdr resistance has also been reported in the M form in Ghana and Burkina Faso [11, 15].
This entomological survey was designed to answer basic entomological questions concerning the transmission of malaria within the forest-savannah transitional zone in Ghana to serve as baseline work for monitoring transmission dynamics and the impact of malaria interventions in this area.