﻿The 
  British 
  Species 
  of 
  Andrena 
  and 
  Nomada. 
  249 
  

  

  may 
  be 
  entirely 
  absent 
  from 
  large 
  stretches 
  of 
  comitry 
  that 
  

   seem 
  well 
  adapted 
  for 
  them. 
  Both 
  visit 
  the 
  same 
  flowers, 
  

   and 
  varians 
  is 
  also 
  parasitised 
  by 
  N. 
  nificornis 
  ; 
  by 
  some 
  

   writers 
  its 
  parasite 
  is 
  considered 
  to 
  be 
  the 
  typical 
  form 
  of 
  

   this 
  variable 
  Nomada. 
  Stylopisation 
  occurs 
  but 
  rarely. 
  

  

  The 
  variation 
  exhibited 
  by 
  the 
  $ 
  of 
  varians 
  is 
  of 
  a 
  re- 
  

   markable 
  character. 
  One 
  most 
  extreme 
  form 
  was 
  named 
  

   mixta 
  by 
  Schenck, 
  and 
  considered 
  to 
  be 
  a 
  distinct 
  species, 
  

   and 
  indeed 
  its 
  appearance 
  is 
  so 
  very 
  different 
  from 
  the 
  

   typical 
  form 
  that, 
  were 
  no 
  intermediates 
  known, 
  one 
  would 
  

   scarcely 
  think 
  it 
  possible 
  that 
  he 
  was 
  in 
  error. 
  It 
  is 
  partly 
  

   owing 
  to 
  this 
  variation 
  that 
  such 
  confusion 
  has 
  existed 
  

   between 
  the 
  closely 
  allied 
  species 
  of 
  the 
  varians 
  group, 
  for 
  

   Smith 
  referred 
  the 
  mixta 
  form 
  to 
  helvola, 
  and 
  Saunders 
  

   considered 
  it 
  to 
  be 
  synadel'pha. 
  

  

  The 
  following 
  varieties 
  of 
  the 
  $ 
  may 
  be 
  distinguished 
  : 
  — 
  

  

  (i) 
  Typical 
  varians 
  has 
  black 
  hair 
  on 
  the 
  face, 
  and 
  the 
  

   underparts 
  of 
  the 
  thorax 
  are 
  clothed 
  with 
  blackish 
  or 
  

   sooty-grey 
  pubescence, 
  even 
  the 
  floccus 
  being, 
  at 
  least 
  in 
  

   part, 
  sordid 
  in 
  colour. 
  The 
  two 
  basal 
  abdominal 
  segments 
  

   bear 
  bright 
  fulvous 
  hairs, 
  all 
  the 
  others 
  black 
  ones, 
  

   (ii) 
  The 
  fulvous 
  hairs 
  of 
  the 
  abdomen 
  spread 
  over 
  the 
  

   3rd 
  segment, 
  the 
  hairs 
  of 
  the 
  underpaits 
  often 
  become 
  

   paler 
  and 
  the 
  floccus 
  whiter, 
  (iii) 
  Fulvous 
  hairs, 
  generally 
  

   with 
  more 
  or 
  less 
  tendency 
  to 
  become 
  white, 
  cover 
  the 
  

   4th 
  as 
  well 
  as 
  the 
  3rd 
  segment, 
  the 
  facial 
  hairs 
  are 
  

   greyish 
  or 
  whitish 
  'fuscous, 
  the 
  hairs 
  beneath 
  the 
  thorax 
  

   and 
  the 
  floccus 
  either 
  slightly 
  discoloured, 
  or 
  else 
  pure 
  white, 
  

   (iv) 
  The 
  hairs 
  on 
  the 
  1st 
  and 
  disc 
  of 
  the 
  2nd 
  segments 
  are 
  

   fulvous, 
  those 
  on 
  the 
  rest 
  of 
  the 
  2nd 
  and 
  the 
  two 
  following 
  

   white 
  or 
  hardly 
  perceptibly 
  yellowish, 
  those 
  on 
  the 
  face 
  and 
  

   whole 
  underparts 
  of 
  the 
  body 
  mostly 
  snow-white, 
  or 
  at 
  most 
  

   a 
  little 
  yellowish 
  tinted 
  in 
  part. 
  This 
  is 
  the 
  true 
  var. 
  

   mixta, 
  and 
  in 
  its 
  finest 
  condition 
  it 
  is 
  a 
  very 
  beautiful 
  insect. 
  

  

  A. 
  helvola 
  under 
  normal 
  conditions 
  appears 
  a 
  little 
  later 
  

   than 
  A. 
  varians, 
  and 
  superficially 
  is 
  extremely 
  like 
  the 
  var. 
  

   mixta 
  of 
  that 
  species. 
  It 
  is 
  partial 
  to 
  dandelions, 
  from 
  

   which 
  it 
  often 
  collects 
  its 
  pollen, 
  but 
  it 
  visits 
  many 
  other 
  

   plants 
  for 
  this 
  purpose, 
  e.g., 
  Crataegus, 
  Rosa, 
  Fragraria 
  in 
  

   gardens. 
  Euphorbia, 
  etc. 
  It 
  is 
  a 
  decidedly 
  local 
  insect, 
  and 
  

   not 
  always 
  at 
  all 
  common 
  even 
  where 
  it 
  does 
  occur, 
  but 
  will 
  

   probably 
  be 
  found 
  somewhere 
  in 
  most 
  of 
  the 
  southern 
  

   counties 
  of 
  England, 
  and 
  it 
  also 
  occurs 
  in 
  the 
  north 
  (Cumber- 
  

   land). 
  It 
  occurs 
  also 
  at 
  Oxford, 
  but, 
  unless 
  well 
  authenti- 
  

  

  