Mar. 3. 1919 Species of Pegomyia Mining Dock . 239 



Second-stage larva, — The segmentation in the second-stage larva is 

 more conspicuous. The alimentary canal and trachea become obscured 

 by the accumulation of fat and the larva becomes more yellowish in color. 

 The "pseudo-cephalon," as in the previous stage, bears a pair of sensory 

 papillae. In addition, it has a pair of two segmented antennae which are 

 located slightly posterior to the papillae and are not as closely approxi- 

 mated as the latter. The pharyngeal skeleton is stronger and more highly 

 chitinized. The mandibular sclerite is triangular and bears four teeth. 

 The button-like areas on the side of the "pseudo-cephalon" are present 

 but reduced to five in number. Similar to the first-stage larva the inter- 

 segmental areas and edges of the segments posterior to the second are 

 encircled by several discontinuous thickly set rows of minute fleshy loco- 

 motory spines. These become less pronounced posteriorly. There is an 

 anterior spiracle on each side inserted between the second and third body 

 segments. Each spiracle has from 24 to 26 breathing pores arranged 

 about an oval slightly chitinized, flattened disk. The posterior spiracles 

 project slightly and have two narrow breathing pores. The anus opens 

 between two triangular plates on the venter of the last segment. 



Third-stage larva, — When mature the third-stage larva measures 

 from 9 to 9.5 mm. It is yellowish in color, distinctly shiny, and beadlike 

 in shape, especially when viewed from above. There is a reddish area 

 ♦ within the anterior end of the larva which disappears when the larva is 

 preserved in alcohol. The "pseudo-cephalon," as before, bears in front 

 of the mouth opening a pair of two jointed antennae, and in front of these 

 a pair of sensory papillae. Five minute button-like areas are also present 

 on the side of the "pseudo-cephalon." The pharyngeal skeleton is even 

 more highly chitinized than in the second-stage larva. The mandibular 

 sclerite resembles that of the second-stage larva, but bears three teeth. 

 The intersegmental areas and edges of the third to the last segment are 

 encircled with minute fleshy locomotory spines as in the previous stages. 

 The posterior spiracles are borne on short tubercles and have three 

 breathing pores. The anus opens between two triangular plates (PI. 30, D). 

 Table V gives the distinguishing characters of the three larval stages. 



Puparium. — The puparium when first formed is yellowish with a red- 

 dish area at the anterior end similar to that found in the larva. The 

 colored area soon disappears, and in about two hours the puparium 

 becomes reddish brown in color. The divisions of the segments are 

 marked by a grayish powdery substance. The surface of the segments 

 are marked by fine annular striae. The triangular anal plates of the larva 

 are visible in the puparium. The adult in issuing breaks a piece from the 

 anterior dorsal portion of the puparium, including the first, second, third, 

 and part of the fourth segments. The anterior spiracles of the larva are 

 removed Avith the cap, which is broken loose. The mouth hooks of the 



