A C Harrison, the founder of the Cape Piscatorial Society in its present form, kept examples of the most common Western Cape mayflies in aquariums and he found that many if not most species emerged on humid nights which ensured that their wings did not dry out. This also made them less vulnerable to predation. Many caddis species emerge at night and lay their eggs when light levels are low.
At the same time terrestrial insects, in particular ants and beetles, contribute more to trout diet over a season than mayfly and caddis.
Ants are always present throughout the year from dawn to dusk and beetles are present in substantial numbers in early spring.
Furthermore, unlike emerging aquatic insects, which have high escape potential, beetles, ants and hoppers are very vulnerable to capture once they land in the water. For this reason, trout which are selectively locked onto a hatch of aquatic insects will often turn aside to take an ant or beetle because they have become a form of prey that cannot escape.
While terrestrial patterns are usually seen in the context of floating flies, they can be even more deadly when fished as a nymph with strike indicator such as Rio’s new two-tone mono incorporated in a greased leader