Abstract: In order to explore the pattern and significance of swimming, through photos and videos we observed and recorded the swimming behavior of the aquatic larvae of Megaloptera in detail for the first time using the endemic Chinese species Neoneuromus ignobilis Navás, 1932 as the test insect, which were collected from the Dadu River and reared in nature-simulated environments. Four swimming postures are recognized and described herein in detail, i.e., vertical, parallel, back and side swimming, and these postures were used by the larvae disproportionately, with a frequency of 89.08%, 5.49%, 4.40% and 0.61%, respectively. The swimming larvae tend to pose their body into an S-shape, with various degree of sinuation. By changing the directions of the head and tail, they can easily rise up or sink and change swimming postures. The propulsion was generated by the wriggling of the body while the legs were mostly held close to the body. Larvae of different instars varied greatly in swimming ability, the 6th instar larvae being the best and most active swimmer compared to the 2nd and final instars. The larvae may also employ complex defense behaviors not often known from relatively ancient insect groups, like chemical defense as secretion from the end of abdomen.

Key words: Megaloptera, Neoneuromus ignobilis, aquatic insect, larva, swimming behavior, swimming posture