Assessing the impact of delayed density-dependence on natural larval populations of Aedes aegypti and Aedes albopictus

Aedes aegypti and Aedes albopictus are both vectors of dengue fever. The effects of density dependence on larval survival and fitness of these mosquitoes could have major impacts on control programs but rigorous studies under natural conditions are lacking. As a follow up on our studies of direct density dependence in larval stages the current study examined the impact of delayed density-dependence (DDD) in natural populations of Ae. albopictus and Ae. aegypti. Five gallon buckets, commonly used by Aedes were divided in half to allow two treatments, control and experimental, within each bucket. Buckets were placed at houses in Raleigh, NC and Tapachula, Mexico. Buckets were left uncovered, allowing natural food to accumulate and natural mosquitoes to lay eggs and populate the buckets. Eggs and larvae were removed daily from one side of each bucket to mimic larvicidal control. On the other side of each bucket, eggs were allowed to hatch and pupae were collected as they emerged. After five weeks, larvae were removed from both treatments and equal numbers of first instars were added to each half of every bucket. Pupae were collected daily and adults were frozen as they emerged. DDD was expected to result in fewer and smaller pupae from the side where eggs and larvae had not been removed. DDD was significant in Ae. albopictus in NC but not for Ae. aegypti in the dry season in Mexico. Data is currently being collected during the wet season in Mexico. Results of these studies will be used to improve a simulation model of Aedes population dynamics.