﻿The 
  British 
  Species 
  of 
  Andrena 
  and 
  Nomada. 
  275 
  

  

  Group 
  of 
  A. 
  NiGRiCEPS. 
  

  

  The 
  males 
  are 
  easily 
  characterised 
  by 
  the 
  upturned 
  

   tubercle 
  of 
  the 
  labrum, 
  combined 
  with 
  the 
  fact 
  that 
  the 
  

   head 
  lacks 
  the 
  occipital 
  characters 
  of 
  the 
  preceding 
  group 
  

   and 
  the 
  mandibles 
  are 
  never 
  armed 
  with 
  a 
  basal 
  tooth. 
  

   Further 
  the 
  abdomen 
  is 
  distinctly 
  banded 
  with 
  pubescence. 
  

   The 
  females 
  also 
  differ 
  from 
  those 
  of 
  the 
  varians 
  group 
  

   in 
  the 
  distinctly 
  banded 
  abdomen, 
  the 
  less 
  perfect 
  floccus, 
  

   some 
  of 
  the 
  hairs 
  at 
  the 
  base 
  of 
  the 
  trochanter 
  being 
  

   comparatively 
  thick 
  and 
  not 
  much 
  curved. 
  In 
  fuscipes 
  

   alone 
  the 
  floccus 
  is 
  nearly 
  perfect. 
  All 
  the 
  species 
  have 
  

   the 
  hind 
  tibiae 
  unusually 
  wide 
  apically, 
  and 
  the 
  scopa 
  

   on 
  the 
  outer 
  surface 
  of 
  these 
  is 
  formed 
  of 
  hairs 
  that 
  are 
  

   finer 
  than 
  usual, 
  while 
  those 
  springing 
  from 
  the 
  lower 
  

   side 
  are 
  much 
  less 
  conspicuously 
  curved 
  up 
  round 
  the 
  

   outer 
  side 
  of 
  the 
  joint. 
  

  

  Group 
  of 
  A. 
  SERICEA 
  (albicrus). 
  

  

  We 
  have 
  but 
  two 
  species 
  of 
  this 
  group. 
  They 
  are 
  re- 
  

   markable 
  for 
  the 
  pale 
  clothing 
  of 
  the 
  males, 
  which 
  frequent 
  

   sandy 
  places, 
  where 
  the 
  females 
  form 
  their 
  colonies. 
  Though 
  

   not 
  very 
  long 
  and 
  falcate, 
  the 
  mandibles 
  cross 
  at 
  the 
  tips 
  ; 
  

   the 
  head 
  and 
  tubercle 
  of 
  the 
  labrum 
  are 
  of 
  ordinary 
  form. 
  

   The 
  apical 
  margins 
  of 
  the 
  intermediate 
  abdominal 
  dorsal 
  

   segments 
  bear 
  short 
  white 
  or 
  pale 
  hairs 
  forming 
  bands 
  or 
  

   lateral 
  streaks. 
  The 
  inner 
  apical 
  angles 
  of 
  the 
  lobes 
  of 
  

   the 
  stipites 
  are 
  considerably, 
  but 
  not 
  acutely, 
  produced, 
  

   and 
  well 
  separated 
  from 
  one 
  another, 
  the 
  sagittae 
  wide 
  

   at 
  the 
  base 
  from 
  the 
  rounding 
  of 
  the 
  sides. 
  In 
  both 
  sexes 
  

   the 
  basal 
  abdominal 
  segment 
  is 
  shining. 
  The 
  females 
  

   have 
  a 
  perfectly 
  formed 
  floccus, 
  and 
  the 
  abdomen 
  has 
  

   white 
  apical 
  bands 
  on 
  the 
  intermediate 
  segments 
  ; 
  the 
  

   scopa 
  outwardly 
  consists 
  of 
  silvery 
  white 
  hairs 
  or 
  of 
  dark 
  

   fuscous 
  and 
  silvery 
  ones 
  together, 
  and 
  the 
  pygidial 
  area 
  is 
  

   definitely 
  and 
  triangularly 
  raised 
  in 
  the 
  middle. 
  There 
  

   is 
  a 
  dense 
  and 
  distinct 
  apical 
  ciliation 
  of 
  the 
  ^ 
  ventral 
  

   segments. 
  

  

  Group 
  of 
  A. 
  FULVAGO. 
  

  

  The 
  alliance 
  between 
  the 
  two 
  species 
  fulvago 
  and 
  polita 
  

   is 
  doubtful 
  and 
  certainly 
  not 
  very 
  close, 
  the 
  differences 
  

   between 
  the 
  male 
  genital 
  armatures 
  being 
  considerable 
  

   and 
  perhaps 
  important. 
  The 
  flagellum 
  in 
  the 
  (^ 
  of 
  both 
  

  

  