Résumé:
Third and fourth instar larvaes of Culex pipiens L. mosquitos have been exposed, in laboratory
conditions, to aqueous extracts from eight plants in different concentrations in order to evaluate
their larvicidal effect.
The results indicate variable sensibility levels of larvaes, which are relatively higher when
extract concentration is raised. However, the toxicity is well observed when the larvaes are
exposed for extended periods of time. Of all the extracts tested, Eucalyptus and Oleander seem to
be more efficient in the fight against these mosquitos.
As for intestinal study, we have determined the several histological modes of action of toxic
elements of extracts on the intestinal tissue of the treated larvaes.
Effectively, the microscopique observations on the treated larvaes on time intervals of 2h, 6h,
12h, 24h, reveal radical modifications as time goes. Such as, after 24h the cells explode and the
cytoplasmic content passes through the intestinal lumen, which lead to death.
Different morphometric parameters have been considered, such as: length and width of wings,
length and width of the abdomen, length of antennas, femur, tibia and the 5 tarses of adult Culex
pipiens that were treated with plant extracts.
Data analysis shows that aqueous extracts of plants induce some differences in comparison to the
control`s parameters.
