608 PEOF. E. B. POULTON : NATURAL SELECTION 



freely exposed at rest as well as in flight. This is brought about by 

 a reduction of the elytra to small oval scales. Hence the resemblance 

 which is so largely due to the colouring of these parts in Plagio- 

 Tiotus is here in an allied form due to the appearance of parts 

 which are concealed, except during flight, in the former. It is also 

 to be noted that the exposed under wings have the dark tint, which is 

 so common in the species of stinging Hymenoptera, and that such 

 exposure of the functional wings is very unusual in Ooleoptera and 

 is almost, if not entirely, confined to the species in which their display 

 is made part of a mimetic resemblance. 

 Fig. 5. Natural size. An Australian species of Esthesincs, Esthesis ferrugineus. 

 In this beetle the elytra are reduced to squarish scales and the under 

 wings freely exposed at rest. The bold and characteristic colouring 

 is found in many Australian insects of which three other examples 

 are figured here. 

 Pig. 5 A. Natural size. An Australian fly, a species of Basypogon {Aailid^), 

 with the same type of colour and pattern as that of the last and the 

 two succeeding figures. This Dipterous insect resembles the wasp 

 represented in fig. 5 b with especial closeness. 

 Fig. 5 B. Natural size. An Australian wasp, Abispa australis {Eumenida), 

 which is in all probability the central type of this characteristic 

 Australian group. 

 Fig. 5 c. Natural size. Another Australian wasp, Eumenes Latreillei (Eumenid<s), 

 which falls into this group. Other species of Australian wasps are 

 also included, and probably additional insects of other Orders from 

 the same region will be found to possess a similar type of colouring. 

 Fig. 6. Natural size. A Brazilian species of EhinotragincB, Isthmmde hraco- 

 noides, in which the very slender form strongly suggests the ap- 

 pearance of a Hymenopterous insect. The colouring and pattern of 

 the wings is very rare in beetles, and is in all probability mimetic of 

 some stinging insect from the same part of the world. The elytra 

 are here reduced to linear vestiges somewhat broadened at their 

 bases ; they leave the under wings freely exposed. 

 Fig. 7. Natural size. A species of Hephastion sp. {KecydalincB) from Chili. 

 The appearance is extremely wasp-like, and is brought about by a 

 reduction of the elytra vei'y similar to that indicated in the last 

 figure. The under wings are dark like those of so many wasps, and 

 the whole appearance most suggestive of a stinging insect and unlike 

 that of a beetle. 

 Thus in this Plate five species of nearly related Longicorn beetles are 

 represented. The appearance of a wasp is chiefly suggested by the colouring 

 of the fully developed elytra of one species (fig. 3), by the reduction of the 

 elytra and form and colour of the parts thus displayed, in all the rest (figs. 4, 

 6, 6, & 7). Furthermore the elytra are reduced to oval remnants in one (fig. 4), 

 squarish in another (fig. 5), and linear (with broader bases) in the remaining 

 two (figs. 6 & 7). Stout-bodied black and yellow wasps, such as those of the 

 genus Vespa (or the Abispa shown in fig. 5 b), are resembled by two (figs. 3 & 5), 



