16 



BULLETIN 1107, U. S. DEPARTMENT OF AGRICULTUEE. 



also passed into this scoop, the short length of mine between the 

 larva and the packed borings being left open. The mining con- 

 tinues, the larva rolling from side to side, until the abdominal scoop 

 is full of borings. The larva then turns either dorsally or ventrally 

 toward the packed end of the mine and drags the load of borings to 

 it. By thrusting its anal segments forward a number of times it 

 throws the load of borings up to the legs, which pass it on to the 

 mandibles, and these knead it into the mass of borings already 

 firmly packed into the mine. 



If a larva is taken from its mine it is unable to 

 travel in any direction it desires. It can wriggle 

 around and roll over and over, but that is about all. 

 Molts. — A study of the larval mines and cast 

 skins indicates that the larva molts six times be- 

 fore it pupates. The first molt takes place after 

 the larva has mined a distance of from 2 to 5 mil- 

 limeters from the eggshell, the second from 8 to 

 15 millimeters, the third from 21 to 33 millime- 

 ters, the fourth from 57 to 69 millimeters, the 

 fifth from 130 to 142 millimeters, the sixth from 

 250 to 290 millimeters, and pupation at about 500 

 to 580 millimeters. 



PrejJUjjol larva. — ^When the larva becomes full 



grown it straightens out, becomes shorter, 



broader, and sluggish, and enters a quiescent 



stage. No distinct pupal cell is made. The 



"^Tead^aMf^'Srer"! P^epupal larval skin gradually turns transparent, 



Pupa. Enlarged 8 showing the pupa within. In about six days the 



*™'^^' skin breaks at the back of the head and slowly 



sheds down the head, thorax, and abdomen to the caudal end, where 



it adheres to the caudal segments of the pupa. 



The Pupa. 



The pupa is milk white at first. (Fig. 12.) In from two to four 

 days the eyes and mandibles start to color light brown. The tu- 

 bercles on the prothorax also are faintly indicated. In from four 

 to seven days the eyes and mandibles have turned dark brown, the 

 prothoracic rugosities a light brown, and the mouthparts, antennae, 

 prothorax, and legs show some color. In from 10 to 15 days the 

 tubercles have attained the normal black of maturity, the mouth- 

 parts, antennae, and legs have become light amber, and the tibial 

 teeth and spurs dark brown; the prothorax has changed to brown, 

 the abdominal sternites to a light brown, and the abdominal tergites 



