100  SMITHSONIAN    MISCELLANEOUS    COLLECTIONS  VOL.    96 
It  is  possible  to  conceive  of  the  acriclid  phallus  as  an  extreme  devel- 
opment of  the  gryllid  type  or  organ,  as  does  Walker  (1922),  in  which 
the  dorsal  cavity  and  the  endophallic  cavity  have  united  to  form  the 
common  inner  sac ;  but  the  simple  development  of  the  organ  in  the 
nymph  does  not  bear  out  this  interpretation. 
The  developing  phallus  in  the  various  instars  of  the  acridid  nymph 
is  always  entirely  concealed  in  the  genital  chamber  beneath  the  cover- 
ing pallial  fold  (fig.  42  G,  Pal)  ;  the  latter,  therefore,  must  be  removed 
in  order  to  study  the  growth  of  the  genital  organ.  In  a  young  nymph 
of  Dissostcira  Carolina  (fig.  42  A)  in  which  the  wing  pads  do  not  yet 
project  from  the  angles  of  their  tergal  plates,  the  phallus  has  the  form 
of  a  simple,  bilobed,  conical  papilla  arising  anteriorly  from  the  floor  of 
the  genital  chamber  (B).  The  two  lobes,  or  phallomeres  {Plun),  are 
closely  appressed,  and  from  their  united  bases  arises  a  short  ejacu- 
latory  duct  connected  with  the  ampullae  (Amp)  of  the  vasa  deferentia. 
This  same  stage  in  the  development  of  the  phallus  of  Mclanoplus 
differentialis  is  described  and  figured  by  Else  (1934).  At  a  somewhat 
later  stage,  as  shown  in  Melanoplus  mexicanus  (C),  the  two  phallic 
lobes  {h,  h)  have  lengthened  and  have  been  carried  out  upon  a  com- 
mon basal  part  (c) .  In  an  older  nymph  having  the  hind  wings  reaching 
slightly  beyond  the  middle  of  the  first  abdominal  tergum,  the  phallus 
shows  distinctly  the  beginning  of  adult  diiTerentiations  (D),  but  the 
specimen  here  shown  was  exposed  by  removal  of  the  outer  cuticula, 
and  therefore  belongs  to  the  following  instar.  Dorsally  there  is  a 
sharply  defined  anterior  margin  of  the  epiphallus  (Epph),  a  central 
depression  (c)  in  the  phallobase,  and  a  distinct  basal  fold  (bf).  On 
the  under  side,  the  ventral  lobe  (vl)  appears  as  a  small  transverse 
fold,  above  which  is  the  opening  of  an  already  well-developed  endo- 
phallic pouch.  When  the  wing  pads  reach  to  or  slightly  beyond  the 
middle  of  the  third  abdominal  tergum,  the  end  of  the  abdomen  has 
the  adult  characteristics  (F),  and  a  section  (G)  shows  the  phallus  in 
the  mature  position.  The  epiphallic  region  of  the  phallobase  is  now- 
well  demarked  (H,  Epph),  the  central  depression  {c)  deepened,  and 
the  basal  fold  {hf)  much  enlarged.  The  two  processes  of  the  dorsal 
lobe,  which  in  M.  nicxicamis  remain  distinct  from  the  early  nymph 
(C)  to  the  adult  (I),  are  differentiated  into  proximal  and  distal  parts 
(E,  H,  m,  r),  and  the  ventral  lobe  {vl)  projects  beneath  their  bases. 
Between  this  stage  (H)  and  the  adult  (I)  the  basal  structures  take 
on  their  definitive  form,  and  the  various  details  of  the  aedeagal  lobes 
are  developed. 
The  development  of  the  acridid  phallus  thus  clearly  shows  that  the 
complex  phallic  apparatus  of  the  Acrididae  has  essentially  the  same 
