﻿The 
  British 
  Species 
  of 
  Andrena 
  and 
  Nomada. 
  237 
  

  

  so 
  that 
  the 
  evidence 
  that 
  exists 
  is 
  clearly 
  in 
  favour 
  of 
  the 
  

   Andrena 
  as 
  host, 
  especially 
  as 
  on 
  the 
  Continent 
  its 
  burrows 
  

   have 
  actually 
  been 
  seen 
  to 
  be 
  entered 
  by 
  the 
  parasite. 
  

  

  S. 
  pellucidus 
  (pilifrons) 
  is 
  a 
  constant 
  parasite 
  of 
  A. 
  

   sericea, 
  but 
  is 
  more 
  local 
  than 
  the 
  host. 
  It 
  is 
  interesting 
  

   to 
  note 
  that 
  though 
  this 
  Andrena, 
  like 
  labialis, 
  is 
  generally 
  

   found 
  provisioning 
  its 
  cells 
  in 
  May 
  and 
  June, 
  the 
  Sphecodes 
  

   parasitic 
  on 
  them 
  differ 
  in 
  their 
  habits 
  from 
  one 
  another. 
  

  

  S. 
  nd)icundus 
  appears 
  in 
  both 
  sexes 
  in 
  May 
  and 
  June 
  

   and 
  has 
  no 
  later 
  summer 
  emergence, 
  the 
  females 
  not 
  

   hibernating, 
  while 
  only 
  females 
  of 
  S. 
  pellucidus 
  are 
  found 
  

   at 
  the 
  time 
  when 
  A. 
  sericea 
  is 
  at 
  work, 
  these 
  being 
  hiber- 
  

   nated 
  individuals 
  of 
  that 
  sex 
  which 
  have 
  survived 
  from 
  the 
  

   brood 
  of 
  both 
  sexes 
  that 
  appeared 
  in 
  the 
  later 
  summer 
  

   months 
  of 
  the 
  preceding 
  year. 
  This 
  indeed 
  accords 
  with 
  

   the 
  normal 
  life-history 
  of 
  the 
  genus, 
  but 
  the 
  case 
  of 
  S. 
  

   spinulosus 
  alone 
  as 
  regards 
  the 
  time 
  of 
  emergence 
  is 
  similar 
  

   to 
  that 
  of 
  ruhicundus, 
  and 
  is 
  the 
  more 
  remarkable 
  because 
  

   it 
  is 
  a 
  parasite 
  on 
  Halictus, 
  the 
  species 
  of 
  which 
  genus 
  

   agree 
  in 
  the 
  time 
  of 
  their 
  emergence 
  and 
  in 
  the 
  hibernation 
  

   of 
  their 
  females 
  with 
  normal 
  Sphecodes. 
  Consequently, 
  

   S. 
  spinulosus 
  differs 
  greatly 
  from 
  the 
  normal 
  habits 
  of 
  its 
  

   genus 
  in 
  its 
  life-cycle 
  and 
  also 
  in 
  like 
  manner 
  from 
  its 
  

   host 
  ; 
  S. 
  pellucidus 
  resembles 
  its 
  congeners 
  in 
  this 
  respect 
  

   but 
  differs 
  greatly 
  from 
  its 
  host 
  ; 
  while 
  S. 
  ruhicundus 
  

   differs 
  from 
  the 
  normal 
  of 
  its 
  congeners 
  but 
  resembles 
  its 
  

   host. 
  All 
  other 
  of 
  our 
  Sphecodes, 
  so 
  far 
  as 
  has 
  been 
  ascer- 
  

   tained, 
  are 
  parasitic 
  on 
  Halictus 
  and 
  have 
  the 
  same 
  habits 
  

   as 
  the 
  latter, 
  in 
  so 
  far 
  as 
  males 
  and 
  females 
  emerge 
  together 
  

   after 
  midsummer, 
  the 
  males 
  dying 
  before 
  winter 
  and 
  the 
  

   females 
  hibernating. 
  

  

  The 
  parasitic 
  Strepsiptera 
  of 
  the 
  genus 
  Stylops 
  attack 
  

   many 
  more 
  of 
  our 
  species 
  of 
  Andrena 
  than 
  do 
  the 
  Sphecodes. 
  

   In 
  the 
  Entomologist's 
  Monthly 
  Magazine 
  1918 
  (pp. 
  67, 
  

   115 
  and 
  129) 
  I 
  have 
  given 
  a 
  list 
  of 
  such 
  species 
  as 
  have 
  

   been 
  found 
  stylopised 
  in 
  this 
  country 
  and 
  a 
  synopsis 
  of 
  

   such 
  species 
  of 
  Stylops 
  as 
  are 
  known 
  to 
  me, 
  together 
  with 
  

   an 
  account 
  of 
  the 
  effects 
  of 
  the 
  parasite 
  on 
  the 
  host. 
  The 
  

   Strepsiptera 
  that 
  attack 
  Halictus 
  are 
  a 
  different 
  genus 
  

   from 
  those 
  parasitic 
  on 
  Andrena, 
  and 
  belong 
  not 
  to 
  the 
  

   genus 
  Halictophagus 
  (which 
  is 
  parasitic 
  on 
  Homopterous 
  

   bugs, 
  and 
  was 
  given 
  its 
  generic 
  name 
  under 
  a 
  mistaken 
  

   idea 
  that 
  Halictus 
  was 
  the 
  host), 
  but 
  to 
  Halictostylops 
  or 
  

   Halictoxenus 
  of 
  Pierce. 
  

  

  