30 STRUCTURE OF CERTAIN DIPTEROUS LARV.E. 



In Pegomya Ifrassicse Bouche (figs. 107, 113, 114) and P. plani- 

 palpis Stoin the median tii])eicles of the four in a ro\v are broader 

 than the others and bifid at tip, more (k'eply so in P. hrassicse than in 

 P. planipalpis, and tlie stigmal phites sho\v a <listinct button; the 

 anterior spiracles have about 10 k)bes. In a Pegonn/a from Alaska, 

 taken from cauliflo^'er, the median tubercles of the four in a row 

 are very broad and trifid at tip. 



In Pegomya rujiceps Stein the body is shorter and stouter, and 

 with many swollen areas and transverse lines; the anterior spiracles 

 have about 12 lobes; the median tubercles of the four in a row are 

 much smaller than the others; the stigmal plates are slightly ele- 

 vated, each with the three radiating slits, but no distinct button. 



The larva of Pegomya &iroZor Wied. (figs. 110, 112) has all the 

 tubercles at tip of body small; the four in a row are all equally small; 

 the stigmal plates as shown in figure 112; the anterior spiracles rather 

 large, and with about 12 small lobes; there is a swollen area of ridges 

 all around each segment from the fourth backward. A larva, sup- 

 posedly an anthomyiid, on roots of roses, shows at tip (fig. 117) 

 four large processes; the stigmal plates being on the inner base of 

 the smaller processes. 



Carpenter has figured in Pegomya hetK Curtis two prominent 

 teeth on the great hooks; the anterior spiracles with eight lobes, 

 and the stigmal plates far apart. 



Hewitt has published a fine account of Antliomyia radicum L.; no 

 teeth on the great hooks; anterior spiracles with 13 lobes; stigmal 

 plates near each other, and with three rather long slits; the median 

 tubercles of the four in a row are smaller than others and situated 

 a little nearer the stigmal plates; each is bifid at tip; no button is 

 shown on the stigmal plates. 



In Phorbia foccosa Macq. (figs. 108, 109) the stigmal field is 

 margined by 12 conical processes, and the anal tubercle is in the 

 form of two similar conical processes; the anterior spiracle has but 

 six lobes. 



TRYPETID^. 



In the few forms of Trypetidie examined, those that feed in 

 fruits and soft tissue, there are two mandibles or hooks, the tip of the 

 body is destitute of pointed tubercles, and there is one pair of 

 rounded anal tubercles. The posterior spiracles are similar to 

 those of the Calliphorinse — three simple slits, those of one plate 

 directed toward those of the other. The prothoracic spiracles have 

 numerous lobes, often over twenty, always more numerous than in 

 the MuscidiB or Sarcophagidie. There are no complete bands 

 of spinules around the body, only fusiform areas on the ventral 

 segments; the stigmal area is not noticeal)ly depressed. 



