Phryganea grandis
Phryganea grandis is the biggest Caddis Fly in most of Europe, including Britain. The body is 20 mm in length, but including the wings the animal measures around 33 mm and the wingspan is up to 60 mm. The animal is quite variable: usually the wings are light with a pattern of blackish, greyish or brownish spots. The female has one or more black lines running over the forewings. Males lack these lines and are much smaller. Some animals are hard to identify as they are entirely brownish with little markings. Males of Phryganea grandis can be similar to those of Phryganea bipunctata, another common species. As usual the sexual organs are different. And in this case you don't even have to kill the animal, for the males sexual organ is completely visible when looking from below.
The larva makes a case out of square, equally large pieces of plants. These are spirally arranged, forming a neat case measuring up to 70 mm. The larva moves about on the bottom, but usually hides under a stone or log. When pupation starts it attaches the case on the stem of a plant. Like many other big larvae, the larva of Phryganea grandis is very voracious. When almost fullgrown it may even attack small fish.
Agriotypus sp., an Ichneumonid wasp, is specialised in parasiting on the larva. The adult female wasp goes under water, descending on the stem of a waterplant. On the bottom she searches for larvae. She then deposits an egg inside the case. The wasp's larva hatches and eats the body of the Caddis Fly. She leaves the nervous system intact, so the Caddis Fly will not die. Once the Caddis Fly has attached her case to a plant the wasp will eat the nervous system as well. The Caddis Fly larva dies and the wasp larva starts pupation.
Phryganea grandis is a common species over most of Europe. Despite the size not seen very often. This is mainly due to the fact that the adults are very short lived. Males live a few days only, females up to one week. The larvae are found in still or slowly moving water. Adults are on the wing from May to August.
Fly fishermen call this species the Great Red Sedge or Murragh. These names however are also used for some other closely related species.
