of Lost Parts in the Articulata. 149 



but that commencing as little tubercles they are first elongated 

 to some extent, and that their division into joints takes place at 

 a subsequent period. 



No reproduction of limbs is manifest until the period of change 

 of tegument. Nor does the growth of a newly-formed limb con- 

 tinue apparent after the first few hours or day subsequent to a 

 deciduation of tegument, when the new covering has become con- 

 solidated. The further enlargement of parts is then arrested until 

 the next change. If a limb is lost by the young insect early in life, 

 the newly-produced one grows more rapidly at each change, and 

 ultimately acquires the same size and same number of joints as 

 the normal limb on the opposite side of the body. If, on the 

 contrary, the insect has approached to within one or two changes 

 of its perfect state, then the new part never attains to the adult 

 size or number of joints. 



There are many circumstances which greatly influence the pro- 

 duction of new parts. The chief of these are — the temperature 

 and hygrometric state of the atmosphere, and the health, and 

 quantity of nourishment supplied to the animal. If the tempe- 

 rature of the season is below the average height, or the atmo- 

 sphere be loaded with an excess of moisture; or the insect weak and 

 unhealthy, or not supplied with a proper quantity of food, the expe- 

 riment, usually, will fail. Under the first of these circumstances 

 the insect often dies from exhaustion from loss of blood, owing to 

 the coagulation of effused blood not taking place ; in the latter 

 they have not sufficient power to undergo the change. Healthy 

 insects, in a proper temperature of the atmosphere, usually begin 

 to take food in large quantities soon after the haemorrhage con- 

 sequent on the excision of the old limb has ceased. A greater 

 quantity of nourishment seems always to be required in the re- 

 paration of every severe injury or lesion of structure; as every 

 severe injury always more or less retards, although it does not 

 necessarily prevent, the usual changes. These circumstances are 

 operative to a greater or less extent in different species of insects. 

 Thus some species undergo their changes at a much lower average 

 temperature than others. The common nettle butterfly, on which 

 my first experiments were performed, undergoes its changes at a 

 lower temperature than the peacock, V. Id, the subject of my se- 

 cond set of observations. Vanessa urticce is in general from thir- 

 teen to fourteen days in the pupa state, at a mean highest range 

 of temperature of from 55° F. to 60° F ; but the same insect 

 undergoes its changes in from eight days and a half to nine or 

 ten days in a temperature of from 70° F. to 75° F. The peacock 

 butterfly, Vanessa Id, requires naturally a higher temperature for 

 its development than V. urticce ; it comes forth, as is well known, 

 later in the season and nearer midsummer. It usually is fully 



