816 STUDIES IN AUSTRALIAN NEUROPTERA, vii., 



In attempting to estimate the practicability of sucli a sugges- 

 tion, we have to bear in mind certain factors that must, at the 

 best, very much limit tlie efficacy of the Psychopsidce : — 



(1) Although a single larva of Ps. eleyans, during its life, 

 would most certainly consume a considerable number of Codlin 

 Moth larvae, yet the value of this is much discounted by the 

 long life of the larva, which takes up the best part of two years. 

 The economic value of this insect would be many times enhanced 

 if it were al^le to pass througli all three larval stages in a few 

 weeks, as is the case with the Chrysopidce and Hemerobiidce. 



(2) The larva requires rough-barked trees to live in. Thus it 

 would seem that it could only be successfully introduced into 

 orchards in which the trees were of considerable age. Such trees 

 would probably afford the requisite amount of shelter to tlie 

 larva, which would certainly take heavy toll of anj" other insects 

 that attempted to hide away in the crannies and crevices of the 

 bark. 



(3) As an archaic survival of a very old stock, the Psychopsidce 

 could scarcely be expected to show that readiness to adapt them- 

 selves to new conditions, that is to be found, for instance, in the 

 more specialised Chrysopidce and Nemerobiidce. Many of our 

 Australian species of these two families have readily established 

 themselves in our orchards and gardens, without any attempt on 

 the part of entomologists to place them there; and are already 

 acting very effectively as checks upon Aphidse and Scale Insects. 

 So far, no similar tendency has been noted in the Psychopsidce; 

 unless, indeed, the apparent increase in the numbers of Ps. 

 insolens in such districts as Killarney and Mount Tambourine, 

 in South Queensland, where orchards are rapidly replacing the 

 original bush, is an indication that this species is beginning to 

 accommodate itself to new conditions. It would be natural to 

 suppose that insects which, in a state of nature, are so rare as 

 the Psychopjsidce, would not take kindly to a change of environ- 

 ment which man might attempt to force upon them. Thus, if a 

 selected orchard of old trees were to be well stocked with Psy- 

 chopsis-hdYvse, one would anticipate that the resulting imagines, 

 after pairing, would return to the nearest pifece of untouched 



