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キーワード:
caddis; first instar; eggs; colonial; net spinning; recruitment; behaviour; web
要旨:
Egg masses of the European net-spinning caddisfly Plectrocnemia conspersa were collected from a small stream, with the object of studying egg incubation and early (first seven days) larval behaviour. Egg masses contained 150-800 eggs (mean 440.2, 95%CL 75.6). Egg incubation period in the laboratory (6 days) was related to temperature (X degree C) by the equation ln(y) = 3.14 + 0.144 ln(x), taking 93 days at 6 degree C and 20 days at 18 degree C. Egg masses incubated in the field hatched as predicted by this equation. The length of individual eggs increased by an average of 17% during incubation. Emergence from the egg took about 30 min, and newly hatched larvae had yolk in their guts which lasted 24-30h, after which feeding began. Larvae took only live prey. In still water, larvae span silk, ventilated using abdominal undulations, turned in the net, and performed further miscellaneous movements.
