The Bulletin. 



21 



life cycle of the insects. First, the egg, which is laid by the adult 

 and from which an active, usually rapid growing "nymph" is hatched. 

 This "nymph" is wingless, and from it, without any intermediate 

 resting stage, the winged adults develop. Grasshoppers may be taken 

 as an illustration of insects of this class. The wingless young are 

 familiar objects to every one. It is this stage of insects with in- 

 complete change of form that are known as "nymphs." (Fig. 7.) 



Fig 7 —Life-history of the Grasshopper (all figures enlarged), (a) Egg (redraivn from Riley); 

 (b) nymph (original illustration) ; (c) adult (original illustration). 



Insects belonging to the second class have four stages in their 

 life-history. Eggs laid by the adults develop into larva, or worms, 

 as they are commonly known. Horn Worms may be taken as an ex- 

 ample of this stage in the development of insects of this class. The 

 larvae is the active growing period, and is followed by a resting period 

 which is known, technically, as the "pupa" or "chrysalis" From 

 this pupa, after a length of time, the adults emerge. (Fig. 8.)^ 



It is necessary for the farmer to know the details, the life-history, 

 of the insect he is trying to conquer in order that he may fight it 

 intelligently. Many insects are practically uncontrollable except for 

 a very brief period or a short stage in their life-history. These va- 

 rious details of the life-histories of the tobacco pests will be considered 

 under their proper headings. 



