806     ENNOMOS  SUBSIGNARIA,  OR  THE  MEASURING  WORM. 
About  the  last  of  June  they  commence  preparing  for  the  change 
to  the  chrysalis  state,  previous  to  their  final  transformation,  by 
weaving  a  cocoon  among  the  leaves,  in  which  they  remain  until 
the  beginning  of  July.  The  chrysalis  is  about  seven  and  a  half 
lines  in  length  ;  the  body  is  rough  and  obtused  before,  and  is 
acute  behind,  armed  with  six  brown  hooks.  The  case  of  the  an- 
tennae and  wings  are  well  marked,  of  a  pale  brown  color,  and  are 
fastened  by  silken  threads  to  the  leaves.  The  imago  appears  as 
a  white  moth ;  the  wings  expanding  about  eighteen  lines. 
This  species  is  sometimes  called  Greometra  niveo-sericearia,  or 
the  snow-white  silky  geometer.  The  female  is  impregnated  from 
two  to  five  days  after  her  emergence,  and  is  quite  inactive  after 
delivery.  The  males  live  several  days  afterward.  The  eggs  are 
of  a  green  color,  insoluble  in  water ;  they  remain  on  the  bark  of 
the  tree  till  the  next  June.  They  are  about  half  a  line  in  diame- 
ter, and  at  this  time  are  of  an  olive  color.  They  are  compressed 
at  the  upper  end,  and  are  closed  by  an  oval  flattened  lid. 
Two  parasitic  insects  feed  upon  these  larvae : 
L  The  Ichneumon  fly,  described  by  Guy  in  the  first  volume 
of  the  Boston  Journal  of  Natural  History  ; 
II.  The  Cryptus  conquisitor. 
These  worms  are  a  great  annoyance,  not  only  with  regard  to 
the  havoc  which  they  cause  among  the  leaves,  but  in  consequence 
of  the  peculiar  manner  in  which  they  suspend  themselves ;  they 
are  continually  dangling  in  our  faces,  or  cracking  beneath  our 
feet.  Many  remedies  have  been  suggested  for  ridding  our  cities 
of  these  insects.  The  most  efficient  way  is  to  shake  the  trees 
well  when  the  caterpillars  are  in  a  state  of  suspension  ;  or  apply 
a  mild  alkaline  solution  upon  the  bark  of  the  trees,  which  loosens 
the  eggs,  that  are  glued  to  the  bark  by  a  kind  of  fluid,  ejected 
with  them  at  the  period  of  delivery. 
Properties. — The  larvae  are  cineritious  in  color,  very  much 
wrinkled  when  dry.  The  head  of  a  red  color.  The  powdered 
larvae  are  chocolate-colored,  possessing  a  foetid  narcotic  odor, 
also  a  slight  bitter  taste.  Having  treated  the  powder  of  the 
dark  worms  alone  with  various  solvents,  I  give  the  following  re- 
sults : — 
