Laboratory Growth of <i>Anopheles gambiae</i>(Diptera: Culicidae) and Morphological Determinism of Moulting

Growth in arthropods in general and in insects in particular, is supposed to be discontinuous and occurs during moulting. In Culicidae in general and Anopheles in particular, the number of moults is five with the fourth which gives the pupae. It is known that moulting in insects is a genetic and physiological phenomenon. Most physiological reactions are triggered by chemical or physical stimuli. The pressure exerted by the growth of the larval body on the exocuticle is one of the triggers of moulting. The objective of this work was therefore to determine the exact timing of the first three moults that determine the growth of An. gambiae larvae from egg hatch to pupation to highlight the role of increased larval size in the stimulation of moulting. We therefore, undertook to rear larvae of this anopheline species in the laboratory under conditions close to their natural environment from hatching to pupation. The length and width of the head, thorax and abdomen were recorded daily. Data analysis showed that the size of the head and thorax remained constant for the first three days (D0 to D2) of development and abdomen’s length for the first two days and then increased daily until day seven (D7) when it stopped. These observations led us to say that the M1 moult occurs at end of the third day of development and the M3 moult at end of the eighth day;the M2 moult could not be determined. All these observations led to the conclusion that the larval growth of An. gambiae has a continuous regimen and the growth of the head and thorax of the larva plays a crucial role in the onset of moulting.