57 



mologists, arrived at the conclusion that there was one generation of 

 the insect in the transition zone, two in the upper austral, and three in 

 the lower austral. By using the conclusions of recent years the writei 

 finds that there is one generation in the transition zone, with often a 

 partial second, two generations in the upper austral, and two in the 

 lower austral, with a possibility of a partial third. 



NATURAL CONDITIONS WHICH TEND TO DECREASE NUMBERS. 



It has often been noted that a sudden fall of temperature is fatal to 

 a large number of the smaller larvw of the codling moth. It has 

 been already noted that Professor Aldrich has recorded such an obser- 

 vation. Hot sunshine and extreme dryness cause many of the pupa3 

 in the case to die. A moist climate aids fungi and bacteria to such an 

 extent that sometimes most of the larvae are killed b}^ them. Larvte 

 that are killed l)y fungous diseases are hard and nnunmitied, and 

 have a whitish appearance. Bacteria cause the internal organs to dis- 

 integrate and the larva to become limp and full of juices of a brown 

 color. 



NATURAL ENEMIES. 



Although the codling moth has many natural enemies, the number 

 as compared with those of other Lepidopterous larvie is comparatively 

 small. This may be accounted for by the fact that the insect through- 

 out the greater part of its life is more or less protected, but when the 

 larvitt have left the fruits and are seeking places in which to spin their 

 cocoons and when in the winged stage the}^ are attacked by numer- 

 ous enemies. Birds are by far the most efficient natural enemies of 

 this insect. Anyone who tries to collect the larvje from the trunks of 

 trees in spring will find very few specimens, l)ut, on the other hand, 

 will find many empty cocoons. The writer has many times in the 

 spring searched persistently for larvse in the rough bark and the more 

 exposed cracks, but found practically none, although many could be 

 secured by cutting into the holes and cracks of the tree. Riley, 

 Walsh, and Slingerland also note this effectiveness, find the amount of 

 good the birds do can only be estimated. The cocoons are always 

 found, and on a close inspection of the bark a telltale hole discloses the 

 story of some woodpecker's work. It has often been noted also that 

 the same birds have made holes or enlarged the cracks in the stubs of 

 old branches for the purpose of digging out the larvre. Plate VIII, 

 figs. 1, 2, 3, shows stubs of branches from an old orchard near Elkton, 

 Md., in which these birds have done efficient work in reducing the 

 number of larvae during the spring. Fig. 2 is especially interesting, 

 as on .close examination it shows the following points: Some time in 

 1900, in the course of pruning the orchard a branch was cut away, 

 leaving the stub, which is 8 inches long. In the following winter and 



