﻿26 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  "extends 
  from 
  southern 
  Wyoming 
  through, 
  western 
  Colorado 
  and 
  

   eastern 
  Utah 
  far 
  into 
  a!^ew 
  Mexico 
  and 
  Arizona. 
  They 
  are 
  bounded 
  on 
  

   the 
  north 
  by 
  Wind 
  Eiver 
  and 
  Sweetwater 
  Mountains^ 
  on 
  the 
  east 
  by 
  the 
  

   Park 
  Mountains, 
  on 
  the 
  south 
  by 
  the 
  Desert 
  Eange 
  Eegion, 
  and 
  on 
  the 
  

   west 
  by 
  the 
  Basin 
  Eange 
  Eegion." 
  This 
  region 
  is 
  '^chiefly 
  drained 
  by 
  

   the 
  Colorado 
  Eiver 
  j 
  but 
  a 
  small 
  area 
  on 
  the 
  northwest 
  is 
  drained 
  into 
  

   Shoshone 
  Eiver, 
  another 
  on 
  the 
  northeast 
  into 
  the 
  Platte 
  Eiver, 
  still 
  

   another 
  on 
  the 
  southeast 
  into 
  the 
  Eio 
  Grande 
  del 
  i^orte, 
  and 
  finally 
  the 
  

   western 
  margin 
  is 
  drained 
  by 
  the 
  upper 
  portions 
  of 
  the 
  Sevier, 
  Provo, 
  

   Ogden, 
  Weber, 
  and 
  Bear 
  Eivers. 
  The 
  general 
  elevation 
  is 
  7,000 
  feet 
  

   above 
  the 
  level 
  of 
  the 
  sea, 
  varying 
  from 
  5,000 
  to 
  12,000 
  feet. 
  The 
  ascent 
  

   from 
  the 
  low 
  desert 
  plains 
  on 
  the 
  south 
  is 
  very 
  abrupt, 
  in 
  many 
  places 
  

   by 
  a 
  steep 
  and 
  almost 
  impassable 
  escarpment.'^ 
  

  

  The 
  streams 
  which 
  traverse 
  the 
  region 
  have 
  their 
  sources 
  in 
  the 
  Wind 
  River 
  Mount- 
  

   ains 
  on 
  the 
  north, 
  in 
  the 
  Park 
  Mountains 
  on 
  the 
  east, 
  and 
  a 
  number 
  of 
  tributaries 
  

   come 
  from 
  the 
  west. 
  In 
  their 
  courses 
  through 
  the 
  plateaus 
  they 
  run 
  in 
  canons. 
  

   These 
  cafions 
  are 
  profound 
  gorges 
  corroded 
  by 
  the 
  streams 
  themselves. 
  The 
  '^country 
  

   rock" 
  is 
  composed 
  of 
  sedimentary 
  beds 
  nearly 
  horizontal. 
  * 
  ^ 
  * 
  The 
  region 
  is 
  also 
  

   exceedingly 
  arid, 
  but 
  the 
  mountains 
  that 
  stand 
  on 
  the 
  rim 
  of 
  the 
  basin 
  precipitate 
  a 
  

   large 
  proportion 
  of 
  moisture, 
  and 
  in 
  this 
  manner 
  streams 
  of 
  comparatively 
  large 
  

   volume 
  head 
  in 
  the 
  mountains, 
  run 
  through 
  the 
  plateaus, 
  and 
  descend 
  rapidly 
  to 
  the 
  

   level 
  of 
  the 
  sea, 
  while 
  the 
  country 
  through 
  which 
  they 
  pass 
  is 
  very 
  meagerly 
  supplied 
  

   with 
  moisture. 
  ^ 
  

  

  The 
  Mountain 
  Eegion 
  comprises 
  the 
  mountainous 
  portion 
  of 
  [N'orthern 
  

   Wyoming, 
  part 
  of 
  Central 
  Colorado, 
  all 
  of 
  Idaho 
  with 
  adjoining 
  portions 
  

   of 
  l!^evada, 
  Oregon, 
  and 
  Washington 
  Territory, 
  also 
  the 
  western 
  half 
  of 
  

   Montana. 
  This 
  region 
  is 
  composed 
  chiefly 
  of 
  high 
  ranges 
  of 
  mountains, 
  

   most 
  of 
  which 
  are 
  partially 
  clothed 
  with 
  forests 
  of 
  coniferous 
  trees. 
  

   There 
  are 
  numerous 
  streams 
  of 
  considerable 
  magnitude. 
  These 
  have 
  

   their 
  sources 
  high 
  in 
  the 
  mountains 
  where 
  there 
  is 
  much 
  rain 
  and 
  

   melting 
  of 
  winter 
  snows. 
  Their 
  lower 
  courses 
  lie 
  along 
  beautiful 
  and 
  

   richly 
  carpeted 
  vajleys 
  that 
  are 
  for 
  the 
  most 
  part 
  destitute 
  of 
  timber, 
  

   and 
  are 
  bounded 
  by 
  low 
  foot-hills 
  covered 
  with 
  bunch 
  grasses 
  and 
  

   artemisias. 
  This 
  region 
  in 
  the 
  lower 
  portions 
  is 
  also 
  quite 
  arid. 
  With- 
  

   in 
  this 
  region 
  there 
  are 
  also 
  quite 
  a 
  number 
  of 
  low 
  basin-like 
  valleys 
  

   that 
  formerly 
  were 
  occupied 
  by 
  lakes. 
  These 
  are 
  for 
  the 
  most 
  part 
  richly 
  

   clothed 
  with 
  grasses 
  and 
  other 
  low 
  vegetation, 
  and 
  are 
  generally 
  drained 
  

   by 
  some 
  mountain 
  stream. 
  They 
  all 
  lie 
  northward 
  in 
  Montana, 
  Idaho, 
  

   and 
  Washington 
  Territory, 
  and 
  are 
  of 
  considerable 
  elevation, 
  varying 
  

   from 
  about 
  3,000 
  to 
  7,000 
  feet 
  above 
  the 
  level 
  of 
  the 
  sea. 
  

  

  Sloping 
  eastward 
  from 
  the 
  foot-hills 
  of 
  the 
  Eocky 
  Mountains 
  towards 
  

   the 
  Missouri 
  and 
  Mississippi 
  Eivers 
  is 
  an 
  extensive 
  tract 
  of 
  country 
  

   known 
  as 
  the 
  Plains. 
  It 
  is 
  for 
  the 
  most 
  part 
  a 
  comparatively 
  smooth, 
  

   treeless 
  tract 
  covered 
  by 
  sparse 
  vegetation, 
  mostly 
  grasses 
  and 
  herbs 
  

   that 
  grow 
  in 
  clumps 
  or 
  clusters. 
  The 
  climate 
  varies 
  in 
  temperature 
  

   as 
  we 
  pass 
  from 
  east 
  to 
  west, 
  and 
  from 
  south 
  to 
  north. 
  The 
  region 
  is 
  

  

  3Maj. 
  J, 
  W. 
  Powell: 
  Preface 
  to 
  Geology 
  of 
  the 
  High. 
  Plateaus 
  of 
  Utah. 
  

  

  