THE LIFE-CYCLE OF THE AQUATIC SNIPE FLY ATHERIX-LANTHA WEBB (DIPTERA BRACHYCERA ATHERICIDAE) IN QUEBEC

The aquatic snipe fly Atherix lantha Webb in the riviere de l'Achigan in the Laurentian foothills of Quebec has a univoltine life cycle. The eggs were laid in great clusters under a small footbridge spanning the river and some 61 000 dead females were observed attached to their egg masses. Upon hatching, the hatchlings fell into the water. There were five larval instars. First-instar larvae appeared in June. Growth was rapid and by September most of the population had reached the fourth instar. Overwintering occurred mainly in the fifth and final instar. On the basis of measurements of the second antennal segment of the larvae, it was concluded that growth follows Dyar's law of constant growth rate between instars (growth rate = 1.31), except between the first two instars, where the growth rate was higher (1.41). In May the full-grown larvae left the river to pupate on the banks and adults were on the wing from mid-May to late June.