FOREST ENTOMOLOGY. 



"With the exception of Orthoptera and Neuroptera, all the other 

 orders are represented in forest entomology. Hence the necessity of 

 versatility in entomological knowledge will be apparent. 



Insects are further arranged into Families, Sub-families or Tribes, 

 Genera, Species, and Varieties. There is, of 

 / course, no sharp distinction between a species 



and a variety. 



In order to understand our subject a little 

 more fully, let us, by way of introduction, 

 briefly consider the life -history and structure 

 of a typical insect. 



It has just been remarked that, as a rule, 

 insects pass through four stages of metamor- 

 phosis viz., egg, larva, pupa, 

 and perfect insect. When an 

 insect passes through all these 

 stages, the metamorphosis is 

 said to be complete. When, 

 however, it does not, as, for 

 instance, in the case of Aphidae 

 or plant-lice, the metamor- 

 phosis is said to be incomplete. 

 Let us follow a typical ex- 

 ample of a complete metamor- 

 phosis, commencing with the 

 egg stage. 



The eggs of insects are always 

 deposited in the immediate vicin- 

 ity of the food for the larvae, as 

 in figs. 1 and 2. In cases of 

 many arboreal insects the eggs 

 are often very difficult to dis- 

 cover. Sometimes they are con- 

 cealed within the buds, in the midribs of leaves, the roots, bark, 

 or other convenient places, according to the food of the larvae. 

 Insects adopt many devices to protect their eggs against Aveather and 

 natural enemies, such as covering them over by a gummy secretion, 

 the shedding of hairs, the formation of cocoons, and so forth. The 

 eggs of insects possess very strong powers of vitality, and frost gener- 



Fig. 1. Eggs of White Ermine 

 Moth (Arctia menthastri) on 

 grass. (Photo by A. Flatters, 

 Manchester.) 



Fig. 2. Eggs of 

 the Lackey Moth 

 (Bombyx neus- 

 tria) on birch 

 twig. Found in 

 Cheshire. 



