320 KEPORT OF THE COMiUSSIONER OF AGRICULTURE. 



owing to improved apparatus, in carrying them through to the aduU 

 state. 



While no general destruction was observed, yet forest trees, and e-'^- 

 pecially evergreen trees, support, each year, hordes of caterpillars, com 

 l)risiug species of different families. In beating the branches of any 

 si)ruce, fir, larch, poplar, or maple, and especially the Oak, a great num- 

 ber and variety of caterpillars are shaken down, and the question arises 

 whether the innumerable host constantly and ordinarily at work from 

 spring time to the fall of tte leaf in our forest trees are really injurious to 

 the tree. It is not improbable that good is done to the tree by these vo 

 racious beings. The process up to a certain limit may be one of natural 

 and healthy pruning, but there is no certainty that the limit may not 

 at any time bo overstepped and destruction ensue. The tree is attacked 

 in a multitude of ways by caterpillars alone. The buds arc eaten by 

 various leaf-rollers (Tortrices), the leaves are rained on the upper and 

 under sides by various Tineids, while the leaves are rolled over in vari- 

 ous ways and in various degrees to make shelter for the caterpillars, or 

 they are folded on the edges, or gathered and sewed together by Tineid, 

 Tortricid, and Pyralid larvai. The entire leaves are devoured by multi- 

 tudes of species of larger caterpillars, belonging especially to the Pyra- 

 lid, Geometrid, Bombycid, and Sphingid moths; while certain speeies 

 prey on the fruit, acorns, nuts, and seeds. 



It is a singular fact that of the great family of Owlet or Noctuid 

 moths, of which there are known to be 1,200 species in this country, 

 very few feed on trees, the bulk of them occurring on herbaceous i)lants 

 and grasses. 



While the smaller caterpillars {Microlepidoptera) feed concealed be- 

 tween the leaves or in the rolls or folds in the leaf, or in the buds, the 

 caterpillars of the larger species feed esposed on or among the leaves. 

 Here they are subject to the attacks of birds and Ichneumon and 

 Tachina flies, which are constantly on the watch for them. And it is 

 curious to see how nature has protected the caterpillars from observa- 

 tion. While the young of the smaller moths are usually green, and of 

 the same hue as the leaves among which they hide, or reddish and 

 brownish if in spruce and fir buds, where they hide at the base of the 

 needles next to the reddish or brownish shoots; the larger kinds arc 

 variously colored and assimilated to those of the leaves and twigs 

 among which they feed. W^ere it not for this they would be snapped 

 up by birds. Of "course, the birds devour a good many, and the prj^- 

 ing Ichneumon and Tachina lay their eggs in a large proportion, but 

 those which do survive owe their safety to their protective coloration. 



Of some twenty or more different species of Geometrid caterpillai's 

 which occur on the evergreen trees, some are green and so striped v.ith 

 white that when at rest stretched along a needle, they could with diffi- 

 culty be detected; others resemble in various ways, being brown and 

 warted, the small twigs of these trees ; and one is like a dead, red leaf of 

 the fir or hemlock. There are several span-worms on the oak, Avhich 

 in color and markings, as well as the tubercle and v.arts on the body, 

 resemble the lighter or darker, larger or smaller knotty twigs ; this re 

 semblance, of course, is in keeping with the characteristic habit of these 

 worms of holding themselves out stiff and motionless when not feed- 

 ing. 



In an entirely different way the various kinds of Kotodontiau cater- 

 pillars, which feed exposed on oak leaves, are protected from observa- 

 tion. They feed on the edges of the leaves, and their bodies are green, 

 with brown patches, so that these irreg.ular spot's, when the caleri)ilhtr 



