New research from UC Riverside  suggests that a hormone required for maturity in insects cannot pass freely through the blood-brain barrier unless supported by a transporter protein. The study contradicts previous scientific belief that says steroid hormones can pass freely through the blood-brain barrier. Scientists also found that blocking the transporter protein gives them a slow death without ever entering adulthood. Using the same gene-altering techniques, scientists can prevent disease-spreading mosquitoes from developing and also help to boost reproduction in beneficial bumblebees.