1018.1 V- II. <;ravkly: Passalidm of (he II VW. 5 



Flightless species consequently tend to bear a strong resemblance to one another, 

 especially as regards the general shape of the body, and Bates (1886, pp. 2-3) divided the 

 Americar) Passalidae into two sections on this character ilone (see below, p. 6). 



The extent of the modifications differs gi'eatly in different species, and the relation 

 which they bear one to another is not always the same. Thus in American species the union 

 of the elytra tends to precede the modification of the metasternum, while in Indo-Australian 

 species the reverse is the case. Similarly, reduction of the dentition, whifh seems to be to 

 some extent associated in American gioups with loss of the habit of flight (see below, p. 9) 

 is only found in Indo-Australian forms (where it reaches its maximum development) among 

 species which show no indication of this. 



Tn the Indian Pleurnrins hmclujplnfllns. in which the wings are fully developed, the 

 union of the elytra is not indicated in t lie pupa and is imperfect or absent in the newly 

 hatched adult. This appears to be the case in .some other .species also, and it .seems likely 

 that the elytra may remain separate thnjughout life in certain individuals. I have not seen 

 pupae of my of the more highly modified .species. 



Genitalia ami Sexual Distinctions. 

 Verv little appears to be known of the genitalia of the Passalidae. Shai-ji and Muir 

 /igi2.pp. 579-^80, pi. xliv, figs. 1 i-iyt) found two forms of male genitalia to exi.st, one in 

 which " the basal piece and the lateral lobes form one piece, either by consolidation or the 

 suppression of the basal piece " and one in which " the tegmen consists of two di.stinct 

 uieces. ths basal piece and the lateral lobes.' The former they found in the genus 

 Aulacocychts, the latter in all the other genera they examined : but their observations were 

 very restricted. I have been able to add to these obsen^ations to some extent ; but the 

 results were not such as to warrant any extensive investigation, since all the genitalia 

 examined proved to be very much alike, except in the Aulacocyclinae. Here both the types 

 described by Sharp and Muir occur, one in one group of the subfamily and the other in the 

 other, showing that the difference they found in Aidacocydus is not a distinctive character 

 of the Aulacocyclinae as a whole, as suggested in my previous paper (p. 191). The only 

 other positive result of my investigations' was a curious fact which emerged in connection 

 with species in which the central tubercle varies greatly in size. In these it was found that 

 the specimens in which it was largest and best developed were females, nnd not mnles .i> 

 would be expected by analogy with other groups. 



Classification, etc., inchiding note< on the structure of tJw mandibles. 

 .\lt hough the Van de Poll collection is a remarkably fine one, it is by no mean.s complete. 

 There can. I think, be little doubt that a considerable number of described genera and species 

 have no separate exi.stence ; but the absence from the collection of such di.>tii,ctive forms as 

 Platijverres intermcdius, and of other well-known sjiecies, affords sufficient proof that the 

 names of the missing forms are not all to be lightly relegated to synonymy. The number 

 of new species in so incomplete a collection, on the other hand, seems clearly to indicate 

 that the Passalidae of the world as a whole are less fully kn<twn than are those of the 

 Oriental Pe<_rinii iloalt with in my previous paper. 



