1 6 NEW YORK STATE MUSEUM 



ceding the full grown condition, but the two may easily be separated by the 

 position of these organs. The fore wings of the adult fold over and con- 

 ceal the hind ones, while in the immature grasshopper the hind wing pads 

 are outside of the fore ones. Many insects like the cockroaches, walking 

 sticks, true bugs and dragon flies develop in this manner, though the earlier 

 stages of all do not resemble the adult so closely as do those of grass- 

 hoppers. There are more marked differences between the nymphal stage 

 of the dragon fly and the adult than obtain in many insects having an 

 incomplete metamorphosis, and these insects are grouped with the others 

 because there is no resting period accompanied by marked changes such as 

 occurs in most insects undergoing a complete metamorphosis. 



Complete )i/e(aiiiorphosis. The most marked changes in development 

 are seen in insects such as moths, butterflies, flies, beetles etc., which undergo 

 what is known as a complete metamorphosis or transformation. Compara- 

 tively few understand the relations existing between the voracious caterpil- 

 lar, the quiet pupa or brightly colored chrysalis and the beautiful moth or 

 butterfly. 



Larva. It is very convenient to distinguish between the young of those 

 insects having a complete and an incomplete metamorphosis and this term 

 is frequently limited to the young of the former class, which are commonly 

 known as grubs, maggots, caterpillars and frequently, though improperly, 

 as worms. The young caterpillar emerges from the egg and at once begins 

 feeding. Thisils the period of growth and most injurious insects commit 

 their depredations when urged by the voracious appetite of adolescence and 

 the several molts occurring during this period are largely to permit increase 

 of size. An impending molt is indicated by the caterpillar appearing dump- 

 ish, neglecting its food, followed later by a retraction of the head from its 

 old case and a consequent swelling of' the thoracic segments. Soon the old 

 integument splits over the newly developed head case, the caterpillar slowly 

 emerges from its old skin, leaving it in a collapsed, shriveled condition. 

 One of the readiest methods of ascertaining if a molt has taken place is to 

 look for the empty head case or to measure the width of the head, since a 



