Determination of the Sex and Age of Fourth Instar Chironomid Larvae
For many aspects of the study of population or molecular genetics of chironomids it is necessary to determine the sex or the stage of development.
Determination of the instar of a larva is generally done on the basis of the width of the head capsule. This requires that larvae at varying times after hatching be measured and the results graphed. These measurements fall into four groups, representing the four instars.
Here I am more concerned with the fourth instar, as this is where it becomes possible to determine the sex of a larva and to accurately determine its age, or phase.
From Wülker and Götz (1968)
This figure shows the "anlagen" or developing adult structures in the 10th and 11th body segments, divided into nine developmental stages from top left to bottom right. The female structures are on the left, covering both segments, while the male structures, on the right, are only in segment 11.
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