﻿169 
  

  

  Tragardh 
  (I). 
  Krusbarskvalstret 
  (Bryobia 
  praefiosa, 
  K. 
  )—Meddelanden 
  

   frdn 
  Centralanstaltens 
  Entomologiska 
  Avdelning, 
  Uppsala, 
  no. 
  17, 
  

   1914. 
  

  

  ^ 
  A 
  review 
  of 
  the 
  literature 
  regarding 
  this 
  mite 
  leads 
  the 
  author 
  to 
  

   the 
  following 
  conclusions 
  : 
  — 
  All 
  the 
  different 
  species 
  described 
  by 
  

   Koch, 
  G. 
  Canestrini 
  and 
  F. 
  Fanzago, 
  Berlese, 
  Tjomas 
  and 
  Garman, 
  

   under 
  the 
  names 
  of 
  praetiosa, 
  speciosa, 
  nobilis, 
  gloriosa, 
  ribis 
  and 
  

   pratensis 
  must 
  be 
  referred 
  to 
  praetiosa, 
  K., 
  being 
  mere 
  variations 
  

   and 
  different 
  instars 
  of 
  that 
  species. 
  

  

  The 
  differences 
  as 
  regards 
  the 
  shape 
  of 
  the 
  cephalothoracic 
  plate 
  

   and 
  the 
  hairs 
  on 
  the 
  front 
  femora, 
  on 
  which 
  Berlese 
  bases 
  his 
  two 
  

   species, 
  are 
  not 
  specific, 
  but 
  only 
  variations, 
  as 
  proved 
  by 
  Oudemans 
  

   and 
  the 
  author. 
  The 
  arguments 
  which 
  Thomas 
  and 
  v. 
  Hanstein 
  bring 
  

   forward 
  to 
  show 
  that 
  ribis 
  is 
  different 
  from 
  praetiosa, 
  namely, 
  that 
  

   Koch 
  mentions 
  only 
  4 
  dorsal 
  hairs 
  on 
  the 
  latter, 
  are 
  not 
  vaUd, 
  because 
  

   Koch 
  in 
  his 
  diagnosis 
  of 
  nobilis 
  distinctly 
  states 
  that 
  the 
  latter 
  has 
  the 
  

   same 
  three 
  pairs 
  of 
  hairs 
  as 
  praetiosa. 
  Von 
  Hanstein's 
  argument 
  

   that 
  ribis 
  is 
  different 
  from 
  praetiosa 
  as 
  described 
  by 
  Canestrini, 
  because 
  

   the 
  latter 
  author 
  has 
  found 
  larvae 
  and 
  nymphae 
  of 
  praetiosa 
  as 
  late 
  as 
  

   July, 
  whereas 
  the 
  propagation 
  in 
  Germany 
  takes 
  place 
  in 
  April 
  and 
  

   May, 
  is 
  not 
  valid, 
  as 
  Marlatt 
  has 
  shown 
  that 
  in 
  the 
  United 
  States 
  the 
  

   breeding 
  period 
  is 
  greatly 
  influenced 
  by 
  latitude 
  and 
  chmatic 
  conditions. 
  

  

  B. 
  praetiosa 
  is 
  spread 
  all 
  over 
  Europe, 
  southwards 
  as 
  far 
  as 
  Egypt, 
  

   northwards 
  to 
  the 
  Arctic 
  regions, 
  and 
  occurs 
  in 
  the 
  United 
  States. 
  

   In 
  Europe 
  it 
  is 
  well 
  known 
  as 
  occurring 
  in 
  moss, 
  under 
  stones, 
  etc. 
  

   but 
  lately 
  it 
  has 
  begun 
  to 
  attack 
  gooseberries 
  and 
  has 
  become 
  a 
  serious 
  

   pest 
  of 
  them. 
  In 
  the 
  United 
  States, 
  on 
  the 
  contrary, 
  it 
  is 
  only 
  

   recorded 
  from 
  several 
  kinds 
  of 
  fruit 
  trees 
  and 
  clover, 
  but 
  not 
  from 
  

   moss. 
  

  

  The 
  cephalothoracic 
  plate 
  does 
  not 
  exist 
  in 
  the 
  larva, 
  which 
  gives 
  

   it 
  a 
  hkeness 
  to 
  the 
  larva 
  of 
  Tetranychus, 
  from 
  which, 
  however, 
  it 
  is 
  

   easily 
  separated 
  by 
  the 
  different 
  shape 
  of 
  the 
  hairs 
  of 
  the 
  body, 
  those 
  

   of 
  Bryobia 
  being 
  flat 
  and 
  scale-like 
  ; 
  in 
  the 
  first 
  nympha 
  (length 
  

   0*34 
  mm.) 
  the 
  plate 
  is 
  indicated 
  by 
  the 
  lateral 
  pair 
  of 
  the 
  4 
  anterior 
  

   hairs 
  being 
  inserted 
  on 
  small 
  prominences 
  ; 
  in 
  the 
  second 
  nympha 
  

   (length 
  •45-0*47 
  mm.) 
  the 
  plate 
  is 
  better 
  developed, 
  although 
  still 
  

   much 
  smaller 
  than 
  in 
  the 
  adult. 
  It 
  is, 
  in 
  consequence, 
  easy 
  to 
  dis- 
  

   tinguish 
  between 
  the 
  different 
  instars 
  mth 
  the 
  aid 
  of 
  the 
  shape 
  of 
  the 
  

   cephalothoracic 
  plate. 
  The 
  hairs 
  of 
  the 
  body 
  are 
  present 
  in 
  the 
  same 
  

   number 
  and 
  position 
  in 
  all 
  instars 
  — 
  4 
  pairs 
  on 
  the 
  cephalothorax, 
  2 
  of 
  

   in 
  which 
  in 
  the 
  second 
  nympha 
  and 
  in 
  the 
  adult 
  are 
  inserted 
  on 
  the 
  plate 
  

   and 
  12 
  pairs 
  on 
  the 
  abdomen 
  ; 
  the 
  hairs 
  of 
  the 
  adult 
  are 
  broader 
  than 
  

   those 
  of 
  the 
  larva 
  and 
  of 
  the 
  nymphae. 
  Two 
  pairs 
  of 
  eyes 
  exist, 
  

   contrary 
  to 
  Berlese's 
  and 
  Sorauer's 
  statements 
  ; 
  the 
  tarsi 
  are 
  provided 
  

   with 
  two 
  claws 
  and 
  between 
  these 
  an 
  empodium 
  provided 
  with 
  two 
  

   dense 
  rows 
  of 
  adhesive 
  hairs 
  ; 
  in 
  the 
  adult, 
  however, 
  the 
  first 
  tarsus 
  

   has 
  much 
  weaker 
  claws 
  and 
  greatly 
  reduced 
  empodium 
  o\^dng 
  to 
  the 
  

   first 
  pair 
  of 
  legs 
  having 
  developed 
  into 
  tactile 
  organs. 
  

  

  The 
  propagation 
  of 
  the 
  gooseberry 
  mite 
  takes 
  the 
  same 
  course 
  in 
  

   Sweden 
  as 
  it 
  does 
  in 
  England 
  and 
  Germany 
  ; 
  the 
  eggs 
  hibernate 
  on 
  

   the 
  branches 
  and 
  in 
  the 
  beginning 
  of 
  May 
  the 
  larvae 
  make 
  their 
  appear- 
  

   ance, 
  the 
  greatest 
  amount 
  of 
  damage 
  being 
  done 
  in 
  May 
  and 
  the 
  begin- 
  

  

  