Only one gene, CYP6N12, was over expressed in both PLX4032 larvae and adult females, albeit at lower levels in the latter. The application of temephos against the larval stage is likely to be selecting for the over expression of CYP6N12, and although this molecule may offer residual protection in adults, it is possible that expression gradually diminishes in adults as temephos exposure recedes. CYP4H28 expression was also altered in both life stages but demonstrated a contradictory pattern as it was significantly under expressed in RecR larvae and over expressed in adult females. It is difficult at this stage to make any inferences about the possible role of this particular gene. A number of physiological processes performed by female mosquitoes, such as host seeking, blood feeding and reproduction, may affect the expression of metabolic genes. However, the current study was performed with nonblood fed 3-day old females of RecL and RecR populations, ensuring that the differences observed are the result of resistance rather than to other physiological processes. Molecular assays such as microarrays have helped expand the number of resistance populations screened for genes putatively conferring resistance, so it will be interesting to see whether gene signatures are insecticide specific and/or geographically biased. Over expression of CYP6N12 has been demonstrated in larvae of susceptible Ae. aegypti Bora Bora strain when they were exposed to either sub lethal doses of permethrin, the heavy metal copper, the polycyclic aromatic hydrocarbon fluoranthene and the herbicide glyphosate. GSTx2 over expression was recorded in Bora Bora larvae exposed to the carbamate insecticide propoxur, whilst propoxur, glyphosate and benzo pyrene induce the expression of GSTi1. While the expression of the above P450s and GSTs were induced in the Bora Bora strain, elevated CCEae3A expression was seen in a temephos and deltamethrin-resistant population from Martinique in the West Indies. The cohort of up-regulated genes observed in RecR adults were also over expressed in an Ae. aegypti permethrin resistant strain from Isla Mujeras in Mexico. In the same study, CYP9J32 was also upregulated in a DDT and pyrethroid resistant population from Thailand and in a deltamethrin resistant Vietnamese strain. The crucial question is whether genes identified in microarray studies encode proteins with insecticide metabolizing properties and thus are functionally associated with resistance. In the case of CYP9J32, CYP9J10, CYP9J24 and GSTe2 the answer is yes. All three P450s have deltamethrin metabolizing activity in vitro but whilst CYP9J10 and CYP9J24 can also metabolise permethrin this is not the case for CYP9J32. The fact that some P450s appear to be broad acting whilst others appear to be more specific even within the same insecticide class has also been observed with CYP6AA3 and CYP6P7 from An. minimus and highlights the complexities involved in metabolic resistance.