﻿224 
  Mr. 
  R. 
  C. 
  L. 
  Perkins 
  on 
  

  

  have 
  received 
  names, 
  excepting 
  where 
  the 
  change 
  of 
  colour 
  

   is 
  due 
  to 
  seasonal 
  dimorphism, 
  and 
  in 
  these 
  cases 
  the 
  names 
  

   were 
  given 
  under 
  the 
  supposition 
  that 
  the 
  two 
  forms 
  were 
  

   distinct 
  species. 
  Such 
  cases 
  are 
  A. 
  bimaculata 
  and 
  decorata, 
  

   parvida 
  and 
  rninutula 
  and 
  others. 
  The 
  supposed 
  species 
  

   A. 
  mixta 
  Schenck 
  is, 
  I 
  have 
  satisfied 
  myself, 
  a 
  variety 
  of 
  

   A. 
  varians 
  $, 
  in 
  which 
  white 
  hairs 
  replace 
  the 
  black 
  ones 
  

   on 
  the 
  abdomen, 
  face, 
  and 
  on 
  other 
  parts. 
  More 
  or 
  less 
  

   intermediate 
  conditions 
  are 
  sometimes 
  found, 
  and 
  a 
  similar 
  

   kind 
  of 
  variation, 
  but 
  less 
  extreme, 
  is 
  found 
  in 
  the 
  female 
  of 
  

   the 
  allied 
  species 
  A. 
  synadelpha. 
  In 
  neither 
  case 
  are 
  there 
  

   two 
  forms 
  of 
  male 
  known. 
  All 
  the 
  few 
  species 
  of 
  Andrena 
  

   which 
  have 
  the 
  integument 
  ornamented 
  with 
  red 
  are 
  varia- 
  

   able 
  in 
  a 
  high 
  degree, 
  excepting 
  only 
  A. 
  cingulata. 
  All 
  have 
  

   melanic 
  forms. 
  Smith 
  was 
  of 
  the 
  opinion, 
  that 
  in 
  the 
  case 
  of 
  

   A 
  . 
  hattorfiana 
  * 
  the 
  red 
  forms 
  were 
  produced 
  in 
  hot 
  sum- 
  

   mers, 
  but 
  I 
  do 
  not 
  think 
  that 
  this 
  will 
  prove 
  to 
  be 
  a 
  complete 
  

   explanation. 
  In 
  my 
  observations 
  of 
  this 
  species 
  in 
  Devon- 
  

   shire 
  only 
  once 
  have 
  I 
  seen 
  a 
  red-bodied 
  example, 
  though 
  I 
  

   have 
  observed 
  the 
  bee 
  in 
  at 
  least 
  two 
  summers 
  of 
  extra- 
  

   ordinary 
  heat 
  and 
  dryness, 
  but 
  this 
  specimen 
  of 
  the 
  red 
  

   variety 
  did 
  not 
  occur 
  in 
  either 
  of 
  the 
  dry 
  years. 
  It 
  is 
  

   remarkable 
  that 
  in 
  South 
  Devonshire 
  no 
  red-marked 
  varieties 
  

   of 
  either 
  brood 
  of 
  A. 
  bimaculata, 
  nor 
  any 
  conspicuously 
  

   red-bodied 
  ones 
  of 
  A. 
  marginata 
  have 
  ever 
  occurred 
  to 
  me, 
  

   though 
  in 
  the 
  more 
  eastern 
  counties 
  such 
  are 
  common, 
  and 
  

   those 
  of 
  the 
  latter 
  species 
  are 
  plentiful 
  even 
  in 
  the 
  

   neighbouring 
  county 
  of 
  Dorset. 
  

  

  The 
  dimorphic 
  forms 
  of 
  first 
  and 
  second 
  broods 
  of 
  the 
  

   double-brooded 
  species 
  are 
  in 
  some 
  cases 
  of 
  very 
  great 
  inter- 
  

   est, 
  and 
  those 
  which 
  are 
  in 
  any 
  way 
  remarkable, 
  and 
  some 
  

   even 
  of 
  those 
  which 
  are 
  not 
  so, 
  have 
  varietal 
  names. 
  In 
  

   most 
  cases 
  the 
  difference 
  in 
  structure 
  or 
  appearance 
  between 
  

   the 
  spring 
  and 
  summer 
  broods 
  is 
  far 
  more 
  marked 
  in 
  the 
  ^ 
  

   sex. 
  Saunders 
  suggested 
  that 
  this 
  dimorphism 
  was 
  pro- 
  

   duced 
  by 
  the 
  different 
  food 
  (pollen 
  of 
  quite 
  distinct 
  species 
  

   of 
  plants) 
  supplied 
  to 
  the 
  larvae 
  of 
  each 
  brood 
  ; 
  but 
  there 
  is 
  

   little 
  reason 
  to 
  suppose 
  that 
  this 
  is 
  the 
  cause 
  of 
  the 
  dimorph- 
  

   ism, 
  for 
  we 
  see 
  no 
  such 
  variation 
  in 
  the 
  individuals 
  of 
  a 
  

   single-brooded 
  species, 
  which 
  must 
  often 
  be 
  produced 
  from 
  

  

  * 
  Mr. 
  Morice 
  informs 
  nie 
  that 
  in 
  Mediterranean 
  localities 
  both 
  

   sexes 
  are 
  almost 
  invariably 
  of 
  the 
  red 
  variety. 
  I 
  have 
  a 
  long 
  series 
  

   from 
  Germany 
  with 
  the 
  males 
  of 
  the 
  dark, 
  the 
  females 
  of 
  the 
  red 
  

   form. 
  

  

  