﻿The 
  British 
  Species 
  of 
  Andrena 
  and 
  Nomada. 
  273 
  

  

  of 
  the 
  5th 
  segment 
  are 
  dark 
  or 
  obscure, 
  never 
  clear 
  yellow 
  

   or 
  golden, 
  while 
  the 
  hind 
  tibiae 
  and 
  their 
  scopae 
  are 
  normal. 
  

   As 
  in 
  the 
  ^ 
  ^ 
  the 
  abdomen 
  lacks 
  the 
  pattern 
  exhibited 
  by 
  

   the 
  wilkella 
  and 
  sericea 
  groups. 
  The 
  male 
  genital 
  arma- 
  

   ture 
  is 
  not 
  remarkable, 
  but 
  vaga 
  and 
  angustior 
  differ 
  from 
  

   the 
  others 
  in 
  having 
  the 
  lobes 
  of 
  the 
  stipites 
  more 
  or 
  less 
  

   broadly 
  rounded 
  at 
  the 
  apex. 
  

  

  It 
  is 
  convenient 
  to 
  consider 
  our 
  species 
  as 
  forming 
  two 
  

   subgroups, 
  the 
  first 
  consisting 
  of 
  the 
  (normally) 
  large 
  

   species, 
  the 
  males 
  of 
  which 
  always 
  have 
  the 
  8th 
  ventral 
  

   segment 
  showing 
  a 
  conspicuous 
  hump 
  or 
  projection 
  beneath 
  

   before 
  the 
  apex 
  when 
  viewed 
  laterally 
  {vaga, 
  cineraria, 
  

   nigroaenea, 
  thoracica, 
  nitida) 
  : 
  the 
  other 
  of 
  (normally) 
  

   medium-sized 
  species, 
  in 
  which 
  the 
  outline 
  of 
  the 
  8th 
  

   ventral 
  segment 
  beneath 
  is 
  at 
  most 
  a 
  little 
  sinuate 
  (gwynana, 
  

   ruficrus 
  and 
  angustior). 
  

  

  It 
  must 
  be 
  remembered 
  that 
  the 
  aberrant 
  species 
  anguMior* 
  

   has 
  close 
  allies 
  on 
  the 
  Continent 
  with 
  similar 
  head-char- 
  

   acters 
  (lower 
  occipital 
  angles 
  much 
  produced 
  backwards, 
  

   mandibles 
  long 
  and 
  strongly 
  crossed 
  at 
  the 
  tips, 
  etc.), 
  

   and 
  of 
  course 
  the 
  removal 
  of 
  such 
  species 
  to 
  a 
  group 
  of 
  

   their 
  own 
  would 
  simplify 
  the 
  definition 
  of 
  the 
  nigroaenea 
  

   group. 
  

  

  Group 
  of 
  A. 
  TRIMMERANA. 
  

  

  A 
  very 
  distinct 
  group, 
  the 
  males 
  distinguished 
  at 
  once 
  

   by 
  the 
  fact 
  that 
  either 
  the 
  mandibles 
  are 
  simple 
  at 
  the 
  

   apex, 
  lacking 
  the 
  anteapical 
  tooth 
  seen 
  in 
  all 
  our 
  other 
  

   species, 
  or, 
  if 
  the 
  mandibles 
  are 
  toothed, 
  then 
  the 
  3rd 
  

   antennal 
  joint 
  is 
  very 
  short 
  while 
  the 
  4th 
  is 
  long 
  and 
  

   slender, 
  appearing 
  almost 
  twice 
  as 
  long 
  as 
  the 
  preceding 
  

   on 
  its 
  'shortest 
  side, 
  and 
  the 
  flagellar 
  joints 
  are 
  shining 
  

   beneath. 
  The 
  cheeks 
  at 
  the 
  apex 
  beneath 
  always 
  form 
  

   a 
  distinct 
  slight 
  angle, 
  or 
  else 
  are 
  there 
  produced 
  into 
  a 
  

   spine. 
  In 
  the 
  females 
  the 
  4th 
  antennal 
  joint 
  is 
  never 
  

   transverse, 
  generally 
  appearing 
  subelongate 
  or 
  at 
  least 
  a 
  

   little 
  longer 
  than 
  its 
  width 
  at 
  the 
  base, 
  while 
  the 
  5th 
  is 
  

   always 
  distinctly 
  elongate. 
  In 
  all 
  the 
  forms 
  but 
  one, 
  the 
  

   floccus 
  is 
  notably 
  small 
  and 
  imperfect, 
  but 
  in 
  ferox 
  it 
  is 
  

   well-developed 
  and 
  perfect 
  or 
  almost 
  so. 
  The 
  pygidial 
  

   area 
  is 
  without 
  a 
  sharply 
  raised 
  median 
  triangular 
  area. 
  

   Abdomen 
  always 
  with 
  dense 
  minute 
  surface 
  sculpture 
  all 
  

   over, 
  never 
  polished, 
  the 
  puncturation 
  feebly 
  impressed 
  or 
  

   subgranulate, 
  sometimes 
  practically 
  effaced. 
  

  

  TRANS. 
  ENT. 
  SOC. 
  LOND. 
  1919. 
  — 
  PARTS 
  I, 
  H. 
  (JULY) 
  T 
  

  

  