Mar. 3, 1919 



Species of Pegomyia MitHng Dock 



243 



Third-stag^ larva. — The third-stage larva resembles very much 

 the previous stage, but is a dirty white in color. The locomotory spines 

 on the intersegmental areas are more conspicuous than in the second- 

 stage larva. They are usually rendered visible to the naked eye by 

 means of the dirt which catches between them. As in the previous stage- 

 the " pseudo-cephalon " bears a pair of two-jointed antennae and a pair 

 of sensory papillae in front of the mouth cavity. The anterior spiracles 

 consist of oval slightly chitinized disks surrounded by about 24 breathing 

 pores. On the posterior aspect of the last segment are six small tuber- 

 cles surrounding the spiracles in a semicircle on the ventral side. The 

 posterior spiracles have three breathing pores. 



PuPARiUM. — ^The puparium is white or slightly creamy in color when 

 first formed, but in about two hours it turns dark brown or almost black. 

 When the puparium becomes dry, it turns grayish in color. The two 

 anal plates of the larva are visible in the puparium and are surrounded 

 by a ring. 



COMPARISON OF THE TWO SPECIES 



A comparison of the characters of the two species is given in Table IX. 



Table IX. — Comparison of the characters of Pegomyia calyptrata and P. affinis 



Characters. 



P. calyptrata 



P. affi.nis 



EGGS. 



Color 



Shape 



Reticulations. . 



LARVA. 



Color 



Mouth hooks. . . 

 Sensory papillae 



Posterior end . . . 



PUPARIUM 



Color 



Segmentation . . 



ADULT. 

 Color 



White, glossy 



Pointed at one end 



Polygonal 



Yellow, shiny 



With three teeth 



Close together, smaller than 



antenna. 

 Not distinctly tuberculate . . 



Brown. .. 

 Beadlike. 



Abdomen yelloA\ 

 bluish gray. 



thorax 



White, waxy. 

 Rounded at both ends. 

 Rectangular. 



Dirty white, dull. 



With four teeth. 



Not close together, about same 



size as antenna. 

 Distinctly tuberculate. 



Black. 



Not beadlike. 



Abdomen and thorax gray. 



