NO.    5      MALE  GENITALIA  OF  ORTHOPTEROID  INSECTS — SNODGRASS        7I 
by  a  posterior  extension  of  its  anterior  margin  (D,  e),  wliich  latter 
thus  comes  to  form  a  free  dorsal  fold  (F,  e)  at  the  distal  end  of  the 
phallus,  where  its  upper  surface  is  reflected  into  the  genital  chamber 
wall  above  (x).  Furthermore,  the  armature  of  the  dorsal  cavity  takes 
the  form  of  two  processes  projecting  from  the  mouth  of  the  cavity. 
The  decticine  type  of  phallic  structure  is  illustrated  by  Walker 
(1922)  from  Nebdida  carinata.  Walker  also  regards  it  as  inter- 
mediate between  the  ordinary  tettigoniid  structure  and  the  rhaphi- 
dophorine  structure,  but  he  takes  the  latter  to  represent  the  more 
generalized  form.  Just  the  opposite  view  is  adopted  here,  because 
there  can  be  no  question  that  the  type  of  structure  progressively 
developed  through  the  Decticinae,  Rhaphldophorinae,  and  Gryllidae 
Fig.  28. — Tettigonioidea-Tettigoniidae-Decticinae :  external  male  genitalia  of 
Anabms  simplex  Haldeman. 
A,  end  of  abdomen,  lateral  view.  B,  phallus,  posterior  view,  showing  also 
internal  pouch  (k)  and  muscles  exposed  before  cut  wall  (x-x)  of  genital  cham- 
ber.   C,  floor  of  dorsal  phallic  pouch  and  its  armature. 
For  letter  explanation,  see  fig.  22. 
is  successively  more  and  more  removed  from  the  primitive  structure 
of  the  phallus  shown  in  all  nymphal  forms. 
Anahrus  simplex  (fig.  28)  gives  a  good  example  of  the  decticine 
type  of  phallic  structure.  When  the  phallus  is  viewed  from  behind 
(B)  it  appears  to  consist  principally  of  two  large,  prominent  lateral 
lobes  (//),  between  which  are  the  mouths  of  two  cavities,  one  dorsal, 
the  other  ventral,  separated  by  a  horizontal  partition  {g).  The  upper 
cavity,  from  which  projects  a  pair  of  serrate,  sclerotic  arms  {i),  is 
roofed  over  by  a  membranous  fold  {e)  ;  the  floor  of  the  ventral  cavity 
is  formed  by  the  ventral  phallic  lobe  {vl).  If  the  phallus  is  removed 
from  the  body,  it  will  be  seen  that  the  dorsal  cavity  ("  paramere  sac  " 
of  Walker)  forms  a  large  internal  pouch  (B,  k).  On  opening  the 
membranous  dorsal  wall  of  the  latter,  it  is  at  once  evident  that  the 
floor  of  the  pouch  (C)  is  the  floor  of  the  usual  dorsal  cavity  of  the 
