170 Transactions. 
Авт. 17.—A Monograph of the Psocoptera, or Copeognatha, of New 
Zealand. 
By К. J. TiLLvARD, M.A., Sc.D. (Cantab.), D.Sc. (Sydney), C.M.Z.8., F.LS., 
F.E.S.; Entomologist and Chief of the Biological Department, Cawthron 
Institute, Nelson, N.Z. 
[Read before the Nelson Institute, 16th June, 1921 ; received by Editor, 20th June, 1921; 
issued separately, 17th February, 1923.] 
Plate 18. 
INTRODUCTION. 
THe Psocoptera, or Copeognatha, are a somewhat small but remarkably - 
distinct and well-defined order of insects, having no very close affinities 
with any other group. With the exception of a single family of comparatively 
large forms, the Thyrsophoridae, confined to South America, the order 
contains only small insects, ranging from little more than 1 mm. long 
(wingless forms) to forms having an expanse of wing up to about in. They 
e for the most part beneficial insects, feeding upon fungi, lichens, and 
algae, though some gnaw the outer bark of trees, and two genera at least 
have become world-wide pests of houses—the notorious “ book-lice 
(Troctes and Atropos). 
Morphologically, the order is distinguished by some remarkable characters 
in the form of the head, mouth-parts, thorax, and wings. These may be 
briefly discussed here. 
,'In the mouth-parts, the mandibles are interesting because of their if ot 
tinct asymmetry, the teeth of one fitting into the clefts between those 0 — 
the other. Each mandible carries, besides teeth, a corrugated grindin ft 
chewing plate; and these also are of different shape in right and le 
mandibles. The maxillae are divided into two very distinct parts by 
