372 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



In this city (New York) you have a caterpillar of this class, — 

 the little span-worm, or Geometer, It is unnecessary to describe 

 its personal appearance. This little worm, like many others, is 

 something of a philosopher ) it knows that if the wind should 

 throw it from a high tree, and it had no means of breaking the 

 force of the fall, it would be hurt. Now, to guard against any 

 thing so unpleasant, it lays across its path, wherever it goes, a 

 silken cable ; push it overboard any where, and it will lower itself 

 down deliberately and safely. It has also a kind of hand-over- 

 hand way of climbing back again by the same cord. You may 

 have noticed, also, that, when descending, they drop themselves 

 a little way at a time, and then stop. These silken threads are 

 spun from a fluid, and require some time to dry, otherwise they 

 would not bear the strain. 



Some of us in the rural districts of Jersey read the papers. 

 Once last summer I noticed that the authorities were about to 

 cut down the trees of this city to get clear of the worms. Now, 

 nothing in your newspapers perplexes us so much to understand, 

 as the accounts of your local government. At one time your 

 aldermen are called the "forty thieves;" then they appear to 

 have nothing to do but to seek out the nativity of a fat police- 

 man; and lately they seem to have been mixed up with the Jap- 

 anese ambassadors in some very queer operations ; but when your 

 city governors do order your shade trees cut down to get rid of the 

 little caterpillars, we shall know exactly what manner of men 

 aldermen are, — then we, who pay some attention to classifying 

 the orders of nature, will know precisely where to place them. 



These little Geometers, of your city, like most other caterpillars, 

 feed upon leaves ; they cannot live without them. They are 

 born in the trees ; leaves are plenty, they are all around them 

 every where, and they feel no kind of hesitation about taking all 

 they want. And why should they ? Their mothers selected these 

 trees for them the year before ; and this selection is the result of 

 an instinct the most wonderful of the world of wonders in which we 

 live. She selects from the many those few trees to deposit her 

 eggs upon whose leaves will put forth the next spring just at the 

 right time to afford food for her little ones when they come out 

 of the eggs. In other words, she knows how much caloric is re- 

 quired to burst the buds of trees and the shells of her eggs, and 

 she puts always the right eggs on the right trees. 



If you will now search the bodies of certain kinds of trees in your 



