114 NATURAL HISTORY. [CH. VI. 



which the larva of the wasp takes to prepare for its 

 metamorphosis. How is it that they do not perish? 

 It is a circumstance well worth remarking, that 

 these caterpillars are all of the same size, and 

 all therefore of the same age. It is not to save her- 

 self the trouble of multiplying her journeys that the 

 mother wasp chooses them of a large size, for it is 

 evident that a greater degree of trouble is required 

 to select, than to take at hazard worms of any size. 

 Reaumur conjectures that the wasp is guided by her 

 instincts to choose only those caterpillars which 

 have attained their full growth, and are capable, in 

 consequence, of sustaining a longer fast. Had they 

 been placed in the nest at a younger age, when their 

 appetite called for a plentiful supply of food, it is 

 evident they must have perished ; and thus the mo- 

 ther-wasp would have enclosed the cherished worm 

 in an offensive sewer instead of a cradle furnished 

 with an ample store of appropriate food. 



The mode, too, in which the caterpillars are de- 

 posited is worthy of observation. Had they been 

 huddled together, the worm, instead of finishing the 

 one immediately above, before it attacked the rest, 

 might have nibbled and killed the whole batch, with- 

 out consuming any one entirely, and thus have de- 

 stroyed the caterpillars, and consequently brought 

 on the putrefaction of the food, and so have been 

 doomed to live on carcasses or perish among them. 

 The entrance to the nest is just wide enough to ad- 

 mit the mother-wasp: when she carries in a cater- 

 pillar, she first unrolls it, and holds it in a line under 

 her own belly, and then depositing it at the bottom 

 of the cell, the creature of itself rolls into a ring, 

 the wasp merely taking care to press it down. 

 Reaumur found that the larva spins a cocoon, and 

 remains in it ten or eleven months; it then eats its 

 way through the nest, and comes forth a perfect 

 insect. 



There are var'^us species of American wasps 



