“It is an interesting sight to see a female depositing her eggs. This I have witnessed on several occasions. She deposits an entire row of 10 to 20 eggs and then begins another row. As the rows accumulate, she moves backward over the mass to reach the place for the succeeding rows; thus her body and wings cover the egg mass until it is completed. The eggs are always deposited over water or in a place where the young larvae will naturally fall into water. I found them on the under sides of boat landings, on the under and vertical sides of bridges, on stones projecting above the water of creeks and lakes. Stagnant pools of water are not attractive to members of this genus. The adults do not seem to select the twigs or leaves of shrubs when such objects as those above mentioned are accessible. When a high bridge is selected by the adults, on which to deposit their eggs, they know where the limits of the running water are, and deposit the eggs within those limits.”
Text and drawing © K.C. Davis and the University of the State of New York, and are reproduced from Davis’s Sialidae of North and South America. The caption is from the original publication and the "3x" does not apply to the web image.
More information about the life history of Sialis species is elsewhere on the American Insects web site.
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