92 MAINE AGRICULTURAL EXPERIMENT STATION. I903. 



iinclifterentiated state, and begin to show the characteristics of 

 the male or female organs. The genital ducts, connecting the 

 reproductive organs with the exterior, develop. The larval 

 hypodermis is broken up and the bod}^ wall of the adult is formed 

 frorn the imaginal discs present. The imaginal integument is 

 apparently formed as a secretion from the hypodermis. The 

 escape of the imago from the pupa case is accomplished by the 

 splitting of the case in the mid dorsal line from the anterior end 

 to the region of the thorax. 



THE ADULT INSECT. 



The adult insect (Fig. 46 and 51) measures i to 1.5 millimet- 

 ers from the head to the end of the folded wings. The males are 

 as a rule smaller than the females, and have more slender bodies. 

 The body is yellowish in color. The wings are pure white and 

 each has a single median vein, which in the fore wings has a 

 branch near the base. The legs are long and slender, and are 

 terminated by a two- jointed tarsus which is furnished with three 

 claws. The eyes are four in number, those on each side of the 

 head situated one above the other with a triangular piece of 

 integument extending between them from the posterior side of 

 the head. Above each eye is an ocellus. 



The mouth part consists of a three- jointed rostrum which 

 arises from the back side of the head, and contains on its ante- 

 rior side a groove in which are situated four piercing setae. The 

 setae have a different point of origin from the rostrum, arising 

 farther forward on the head. The antennae are seven jointed. 

 The first two segments are short and stout, the remaining five 

 rather long and slender and covered with ring-like markings. 

 The thorax is very deep and its segments short. The thorax and 

 abdomen are connected by a narrow prolongation of the meta- 

 thorax. 



Digestive System. See Fig. 51. The pharynx, situated at 

 the base of the rostrum, is a narrow tube hardly to be distin- 

 guished from the oesophagus, into which it passes with very little 

 change in size. The oesophagus is a long narrow^ tube extending 

 from the pharynx to the metathorax where it joins the mid- 

 intestine. The mid-intestine runs back to the anterior part of 

 the abdomen where the pair of large diverticula are given off. 



