NO.    5      MALE  GENITALIA  OF  ORTHOPTEROID  INSECTS— SNODGRASS  9 
teruid  insects  (fig.  2D).  These  structures,  being  produced  from  the 
mesodermal  part  of  the  median  outlet  duct,  are  necessarily  themselves 
mesodermal,  and  are  therefore  to  be  classed  as  mesadenia.  They  in- 
clude tubular  accessory  glands  of  various  lengths  (D,  AcGlds),  pro- 
ducing in  most  cases  materials  for  the  formation  of  spermatophores, 
and  saclike  or  tubular  vesictdae  seminalcs  (Vsni)  serving  for  the 
storage  of  the  spermatozoa.  These  organs  do  not  usually  appear 
until  the  adult  moult,  and  sperm  vesicles  may  not  be  formed  at  all  in 
some  families.  The  male  accessory  glands  of  insects  of  certain  other 
orders  appear,  from  ontogenetic  and  structural  evidence,  to  be  of 
ectodermal  origin,  and  therefore  properly  classed  as  ectadenia. 
The  external  genitalia. — The  external  genital  structures  of  male 
orthopteroid  insects  are  principally  phallic  organs.  Accessory  copu- 
latory  structures,  or  periphallic  organs,  are  but  little  developed,  and 
when  present  they  are  mostly  secondary  formations  having  no  appar- 
ent relationships  in  the  different  groups.  Appendage  rudiments  are 
commonly  present  on  all  the  abdominal  somites  of  the  embryo,  but 
in  the  male  those  of  the  somites  anterior  to  the  ninth  disappear  before 
hatching.  The  appendages  of  the  ninth  segment  of  the  male,  however, 
are  retained  in  many  families  as  a  pair  of  small,  nonmusculated  styli 
borne  on  the  posterior  margin  of  the  definitive  ninth  sternal  plate, 
their  coxopodites  supposedly  in  most  cases  being  incorporated  in 
the  sternal  plate.  According  to  Else  (1934)  the  embryonic  appendages 
of  the  ninth  abdominal  segment  of  the  male  of  Melanopliis  differen- 
tialis  merge  completely  with  the  posterolateral  parts  of  the  primitive 
sternum  of  this  segment,  even  the  styli  being  thus  obliterated  in 
Acrididae.  It  is  only  in  the  Grylloblattidae  that  the  ninth  segment  ap- 
pendages retain  a  two-segmented  structure,  the  coxopodites  being 
here  large,  free  lobes  bearing  the  styli  (fig.  6  A,  B,  C). 
The  phallic  organs  of  the  Orthoptera  are  highly  variable  and  often 
very  complex  structures.  In  most  cases  their  principal  modifications 
are  not  adaptations  for  the  direct  intromission  of  the  sperm,  but 
for  the  production  of  spermatophores  and  the  transfer  of  the  latter 
to  the  genital  chamber  or  the  sperm  receptacle  of  the  female.  The 
phallic  structures  of  Blattidae,  Tettigoniidae,  and  Acrididae  can  be 
traced  in  their  nymphal  development  from  small  lobes  that  grow  out 
around  the  mouth  of  the  ejaculatory  duct.  These  phallic  lobes,  or 
phallonieres,  of  Grylloblattidae.  Blattidae,  and  Mantidae  retain  their 
independence  and  take  on  various  forms  in  the  adult ;  in  the  other 
families  they  unite  to  form  a  single  phallic  structure,  or  pJiallus,  which 
contains  an  open  endophallic  cavity  into  which  discharges  the  ejacu- 
latory duct. 
