SACBROOD. 



9 



while its extreme anterior or cephalic end extends almost to the cap 

 and roof. The length of the larva is approximately one-half inch, 

 being nearly that of the cell. Its two lateral sides cover about one- 

 half each of the two lateral walls. The width of the larva is approxi- 

 mately one-fifth of an inch, being the distance between the two 

 lateral walls of the cell. 



The dorsal portion of the larva lies against the floor of the cell, 

 being more or less convex from side to side and also from end to end. 

 Its ventral surface is convex from side to side, and is, generally speak- 

 ing, concave from end to end. Considerable empty space is found 

 between the larva and the roof of the cell. The spiracles are visible. 

 The glistening appearance, characteristic of a larva before capping, 

 very largely disappears after capping. Although larvae at this 

 age might be thought of as white, they 

 are in fact more or less bluish white in 

 color. It is possible to remove a healthy 

 larva at this age from the cell without 

 rupturing the body wall, but care is 

 required in doing so. 



For purposes of description it is con- 

 venient to divide the length of the larva 

 into three parts. These may be denom- 

 inated the anterior (AT), middle (MT), 

 and posterior thirds (PT). 



Anterior third. — On removing the cap 

 from a cell the anterior cone-shaped 

 portion of the larva is seen (fig. 5; PL 

 II, g). The apex of this cone-shaped 

 third is directed upward toward the 

 angle in the roof of the cell, but is not in contact with the roof or the 

 cap. Transverse segmental markings are to be seen. Along a por- 

 tion of the median dorsal line there is frequently to be observed a 

 narrow transparent area. A cross section of this third is circular in 

 outline. The anterior third passes rather abruptly into the middle 

 third. At their juncture on each lateral side, owing to a rapid increase 

 in the width of the larva at this point, there is presented the appear- 

 ance of a "shoulder." 



Middle third. — This third (figs. 6 and 4; PL II, m) lies with its dorsal 

 portion upon the floor of the cell, its axis being nearly horizontal. 

 The ventral surface is convex from side to side, and is considerably 

 below the roof of the cell. This upper surface is crossed from side to 

 side by well-marked furrows and ridges representing segments of 

 the larva. These furrows and ridges produce a deeply notched 

 appearance at the lateral margins. In some of the segments a trans- 

 verse trachea may be seen appearing as a very fine, scarcely per- 

 58574°— Bull. 431—17—2 



Fig. 5.— End view of healthy worker larva 

 in normal position in the cell. Cap 

 torn and tinned aside with forceps. En- 

 larged about 8 diameters. (Original.) 



