Cluster analysis of Anopheles Stephensi fourth instar larvae behavior to explore sequential organisation of larvae movement in a microcosm

Experiments were conducted on 20 fourth instar Anopheles stephensi larvae to explore behavior organisation. Twenty fourth instar larvae were placed in a glass aquarium and filmed using a handy cam video recorder and the recordings analysed in a laptop computer. Data of transitions from one behavior to another for all observations were collated into a matrix of preceding and succeeding behaviors to study sequential organisation and relationship among behaviors. Significant testing for first-order transition was done using G test at P< 0.005 and a kinematic graph constructed from significant transitions. A time budget and transition frequency data constructed for each behavior were subjected to cluster analysis to explore relationship between the behaviors. Result of the analysis showed that fourth instar Anopheles stephensi larvae behaviors occur in clusters in specific locations in their aquatic environment. Furthermore, the sequential organisation of behaviors is influenced by behavior frequency and the amount time a larva spent doing that behavior. When food is kept constant, other factors such as gas exchange requirements, behavior variation due to day-night cycle, presence of a predator, interlarval competition for food and the size of the aquarium (depth and width) maybe determining behavior organization.

Differences in submergence time and alarm reaction rate in Anopheles stephensi, Aedes egypti and Culex pipiens fourth instar larvae in response to vibration stimulus

Studying mosquito larvae behavior can provide insights into developing new ways in controlling vector borne diseases. Feeding is an aspect of larval behavior that has been studied extensively. Surface and underwater feeding behaviors are linked by diving. The larvae use dive behavior to feed underwater or to escape predators. We elicited dive responses in fourth instar larvae of three different mosquito species using vibration stimulus and compared their response rate and submergence time. Marked differences in the response rate and submergence time were recorded for the three species of mosquitoes. These differences can be exploited to develop new larvae control methods to reduce mosquito borne diseases.

Laboratory evaluation of traditionally produced coconut oil as a surface larvacide against Anopheles Stephensi fourth instar larvae

Environmental concerns have resulted in the search for environmentally friendly natural oils for use as mosquito larvacide. Methylated coconut oil has been found to be toxic to mosquito larvae. However, the use of methylated coconut oil is limited by resource constraints in rural communities in Papua New Guinea and other Pacific Island countries where coconut oil is produced by traditional methods. This study evaluated the toxicity of traditionally produced coconut oil to fourth instar Anopheles stephensi larvae. The results showed that traditionally produced coconut oil is toxic to fourth instar Anopheles stephensi larvae. The results showed that coconut oil produced by traditional method is toxic to fourth instar Anopheles stephensi larvae. The coconut oil can be used as a larvacide for malaria vector control in community based programs utilizing community participation in the production and use of coconut oil for large scale use of coconut oil. However, a suitable surfactant needs to be identified.