﻿Species 
  of 
  Simulium 
  /rom 
  the 
  Siamese 
  Hills. 
  587 
  

  

  The 
  antenna? 
  are 
  brown, 
  yellowish 
  white 
  at 
  the 
  base. 
  In 
  

   spirit 
  the 
  abdomen 
  is 
  white, 
  with 
  brown 
  bands 
  posteriorly. 
  

   The 
  legs 
  are 
  banded 
  black 
  and 
  white 
  ; 
  the 
  tarsi 
  or' 
  the 
  front 
  

   pair 
  are 
  much 
  stronger 
  than 
  those 
  of 
  the 
  other 
  pairs. 
  The 
  

   wings 
  are 
  hyaline. 
  

  

  Head 
  velvety 
  black, 
  with 
  golden 
  hairs 
  between 
  and 
  

   behind 
  the 
  eyes 
  ; 
  the 
  face 
  also 
  is 
  black. 
  Antenna? 
  dark 
  

   brown, 
  except 
  the 
  first 
  two 
  segments 
  and 
  a 
  part 
  of 
  the 
  third, 
  

   which 
  are 
  yellowish 
  white. 
  Palps 
  brown, 
  with 
  the 
  exception 
  

   of 
  the 
  second 
  segment, 
  which 
  is 
  black. 
  

  

  Thorax 
  velvety 
  black 
  ; 
  the 
  scutum 
  is 
  covered 
  more 
  or 
  less 
  

   with 
  bright 
  golden 
  hairs. 
  

  

  Wings 
  hyaline, 
  with 
  only 
  the 
  first 
  and 
  third 
  longitudinal 
  

   veins 
  distinct 
  and 
  dark. 
  Halter 
  es 
  yellowish 
  white. 
  

  

  Legs. 
  — 
  Femora 
  and 
  tibise 
  are 
  white 
  at 
  the 
  proximal 
  end, 
  

   dark 
  brown 
  at 
  the 
  distal 
  end. 
  All 
  the 
  tarsal 
  segments 
  of 
  the 
  

   first 
  pair 
  of 
  legs 
  are 
  dark 
  brown, 
  but 
  in 
  the 
  second 
  and 
  third 
  

   pairs 
  the 
  metatarsus 
  is 
  yellowish 
  white 
  in 
  the 
  proximal 
  half, 
  

   and 
  the 
  next 
  tarsal 
  segment 
  has 
  a 
  white 
  spot 
  at 
  the 
  base. 
  

   The 
  penultimate 
  tarsal 
  segment 
  is 
  heart-shaped 
  in 
  all 
  the 
  

   legs. 
  

  

  Abdomen. 
  — 
  In 
  spirit-specimens 
  the 
  first 
  two 
  segments 
  are 
  

   white; 
  the 
  third, 
  fourth, 
  and 
  fifth 
  are 
  white, 
  each 
  with 
  a 
  

   dark 
  brown 
  dorsal 
  cross-band 
  ; 
  the 
  last 
  two 
  are 
  entirely 
  

   brown, 
  darker 
  dorsally 
  than 
  ventially. 
  

  

  The 
  mouth-parts 
  seem 
  to 
  be 
  similar 
  to 
  those 
  of 
  other 
  

   species. 
  The 
  second 
  segment 
  of 
  the 
  maxillary 
  palps 
  has 
  a 
  

   curious 
  little, 
  probably 
  sensory, 
  vesicle, 
  with 
  a 
  minute 
  

   circular 
  opening 
  on 
  the 
  side 
  of 
  the 
  segment. 
  

  

  Simulium 
  nigrogilvum 
  is 
  about 
  the 
  same 
  size 
  as 
  Simulium 
  

   indicum, 
  but 
  it 
  differs 
  from 
  that 
  species 
  in 
  the 
  following- 
  

   points 
  : 
  — 
  (1) 
  The 
  base 
  of 
  the 
  antenna 
  is 
  yellowish 
  white, 
  

   whereas 
  in 
  S. 
  indicum 
  the 
  antennae 
  are 
  entirely 
  dark 
  ; 
  (2) 
  the 
  

   femora 
  and 
  tibiae 
  are 
  half 
  white, 
  half 
  black, 
  but 
  in 
  S. 
  indicum 
  

   they 
  are 
  said 
  to 
  be 
  black-brown 
  ; 
  (3) 
  the 
  first 
  two 
  segments 
  

   of 
  the 
  abdomen 
  are 
  white, 
  and 
  ventrally 
  all 
  the 
  rest 
  of 
  the 
  

   abdomen 
  except 
  the 
  tip 
  is 
  white 
  also 
  ; 
  whereas 
  in 
  S. 
  indicum 
  

   only 
  the 
  first 
  segment 
  and 
  the 
  sternal 
  parts 
  of 
  the 
  next 
  three 
  

   segments 
  are 
  yellowish 
  white. 
  

  

  Simulium 
  nigrogilvum 
  is 
  much 
  larger 
  than 
  Simulium 
  nobile, 
  

   which 
  measures 
  only 
  1'5 
  mm. 
  The 
  other 
  points 
  of 
  difference 
  

   between 
  the 
  two 
  species 
  are 
  as 
  follows 
  : 
  — 
  (1) 
  The 
  antennae 
  of 
  

   S. 
  ncbile 
  are 
  reddish 
  yellow, 
  with 
  black 
  tip 
  ; 
  (2) 
  the 
  thorax 
  

   of 
  S. 
  nobile 
  is 
  said 
  to 
  be 
  almost 
  naked, 
  with 
  a 
  silver-white 
  

   sheen, 
  only 
  a 
  posterior 
  strongly 
  arched 
  cross-band 
  being 
  

   velvety 
  black, 
  whereas 
  in 
  S. 
  nigrogilvum 
  the 
  scutum 
  is 
  

  

  39* 
  

  

  