VIII, B, 1 Mitzmain: Stomoxys calcitrans Linnseus 



DEVELOPMENT OF THE LARVA 



35 



Stomoxys calcitrans remains in the larval stage under or- 

 dinary laboratory conditions for a period averaging tv^^elve days. 

 Between the third and fourth days the larva makes its greatest 

 growth in length. By the sixth day the larva has reached its 

 maximum thickness. 



Table II. — Development of a typical larval Stomoxys. 



Date. 



Period of development. 



April 9 . 

 April 12 . 

 April 13 . 

 April 15 . 

 April 17 . 

 April 21 . 



After hatching- 

 Third day 



Fourth day 



Sixth day 



Eighth day 



Twelfth day 



Full grown 



Lengrth. 



mm. 

 1.0 

 3.5 

 6.0 

 7.0 

 9.0 

 10.0 



Width. 



0.75 

 1.5 

 1.5 

 1.5 



THE FORMATION OF THE PUPARIUM 



The puparium is formed two days after the larva has attained 

 its maximum size, which under ideal conditions is from the 

 eighth to the twelfth day. The puparium is constructed with- 

 out any apparent sloughing or shedding of the larval skin, the 

 process being one of simple contraction. A larva measuring 10 

 millimeters is reformed slightly, and contracts to 5 millimeters. 

 The body is thickened from 1.5 millimeters to 2 millimeters. 

 There is an invagination of the cephalic end bearing the head 

 capsule, and this and the anal end become broadly rounded. 



The full-grown larva is coated with a glossy, slimy cuticle 

 which is pale chrome yellow in color. It lies inert at the begin- 

 ning of the somnus which lasts until the puparium is formed. 

 The viscera wrinkle and disintegrate and assume the yellowish 

 color of the Malpighian tubules and the crecal glands. Soon the 

 color of the cuticle blends with that of the internal structures, 

 becoming pale clay yellow. The only structures now visible are 

 the lines of the trachea and the dark brown anal stigmatse. 

 During the changes indicated the mouth cavity is constantly 

 kept in slight action accompanied by a barely perceptible general 

 telescopic movement. Upon the following day these activities 

 cease, the barrel-like puparium is completed, and no internal 

 organs are visible. With the absence of movement, the buccal 

 cavity has become invaginated and is covered by the cap of the 



