... (includingInsecta), which acquire O2via an elaborate tracheal system. However, werecently identified a functional hemocyanin in the stonefly Perla marginata(Plecoptera) and in the firebrat Thermobia ... proteins that evolved independently fromhemocyanins [4].Although hexamerins might be ubiquitous in insects[14,19–21], hemocyanin appears to be missing in eume-tabolous insects [22]. Here we investigate ... also included 17 selected insect hexamerins, 23crustacean hemocyanins, 4 crustacean pseudohemocyanins,20 chelicerate hemocyanins, 5 myriapod hemocyanins and1 onychophoran hemocyanin in the...