29 



94 species (or nearly one-half) in 8 genera. The total number of 

 species referred to, unaccompanied by descrij^tions, is 33, three 

 of which belong to monotypic genera. As only two or three of 

 this species inhabit parts of Australia from which species are 

 described as new by me, scarcely any clashing of my work with 

 that of the older authors is anticipated. 



Tlie Characteristic Organs. — The various external organs of 

 the Blattaria? are constructed on so uniform a plan that it 

 appears almost impossible to mistake a cockroach for any other 

 kind of insect, even ujDon a most cursory inspection ; the system- 

 atist has therefore to resort frequently to minute variations in 

 order to insure ready recognition of his species. Fortunately 

 these small differences appear to be remarkably constant, and are 

 therefore the more valuable. 



The Head is always more or less retracted, the face flat, the 

 vertex prominent, and the mouth directed rearward, the whole 

 being either entirely concealed under the forepart of the 

 thorax, or only a small portion exposed. The eyes are large, 

 oval or kidney-shaped, and placed more or less obliquely ; during 

 life they appear to be always black. The ocelli are mostly only 

 indicated by two pale coloured spots in front, are sometimes wholly 

 absent, and in the Heterogamidce alone are they developed to any 

 extent. Their form, colour, itc, afford sometimes good subsidiary, 

 specific, or varietal distinctions. Such are likewise ofl'ered by the 

 face (frons), labrum, clypeus and palpi, occasionally notable in 

 their colour markings, although their structure varies little or 

 irregularly. The antenna are always slender, and mostly filiform 

 or setaceous (sometimes sub-moniliform or ciliate), varving in 

 length from less than half that of the body to more than doubly 

 exceeding it. As in other Orthoptera, the mouth parts are not 

 employable for general classification on account of their great 

 uniformity of structure, and are only occasionally made use of. 



The Organs of Flight consist of an anterior pair of more or less 

 leathery or horny elytra, and a posterior pair of much more 

 delicate membraneous wings. One or both pairs may be rudi- 

 mentary, lobiform or entirely absent, and either perfect in both 

 sexes, or only in the male. The absence or more or less rudi- 

 mentary state of them are especially prominent in the Australian 

 insects, and favours the localisation and multiplicity of species. 

 They supply most important distinctions. 



The Elytra, when present, exhibit a system of veins analogous 

 to that of the other genuine Orthoptera, The costal or mediastinal 

 vein is very short, usually terminating within the basal-third 

 of length of the fore margin (costa), and is always branchless ; 

 in some genera it shows a more or less tumid keel beneath. 

 The radial or scapulary vein is free from the base, and emits 



