Fig. 3. — The horse- 

 radish flea-beetle : 

 Egg. Highly mag- 

 nified. (Original.) 



4 BULLETIN 535, U. S. DEPARTMENT OE AGRICULTURE. 



THE EGG. 



The egg (fig. 3) is oval, capsule-like, deep orange in color, with no 

 special characteristic marking or reticulations visible under a 4-milli- 

 meter objective. The following are the measurements taken from 22 

 eggs: Maximum, 0.47 mm. by 0.84 mm.; minimum, 0.26 mm. by 0.43 

 mm. ; average, 0.33 mm. by 0.57 mm. 



THE LARVA. 



The immature larva. — The larva, just after 

 hatching from the egg, is about 1.3 mm. long by 

 0.2 mm. wide ; the color of the entire body is 

 whitish, the head, thoracic plates, and anal plate 

 varying from whitish to pale brown. Within a 

 few hours the head, thoracic plate, and anal plate 

 become darker, and a day or more later turn deep 

 brown. In other major respects, excepting the numerous transverse 

 wrinkles and the relative proximity of the setae, the j^oung larva is 

 very similar to the older larva. 



The mature larva. — The larva (fig. 4), when full grown, is slender 

 subcylindrical, pale yellowish white, with dark brown head, thoracic 

 plate, and anal plate; mandibles 

 distinctly quadridentate ; head 

 with the usual V-shaped epicranial 

 suture and dark median line caused 

 by attachment of » tentorium; five 

 setae on epicranium each side of 

 median line, several setae distrib- 

 uted irregularly about lateral mar- 

 gins of head as shown in figure 4; 

 thoracic plates divided by distinct 

 suture ; row of three setae along an- 

 terior lateral margin of each plate ; 

 one on lateral posterior angle ; four 

 minute setae on posterior inner mar- 

 gin of each plate ; one seta on inner 

 anterior angle; mesothorax with 

 pale chitinous plates bearing setae, 

 two in anterior row. four in pos- 

 terior row, four on slightly elevated 

 pleural area; metathorax similar. 

 The thoracic legs each bear one 

 flaw. 



The abdominal segments bear dorsally three rows of slightly ele- 

 vated chitinous plates, each of which gives rise (when not continu- 

 ous) to a seta; the first row comprises six, the middle row two, the 



if 



Fig. 4. — The horse-radish flea - lnw-i i<> : 

 Larva; at left, dorsal view: al right, 

 lateral view. Tubercles and tubereu- 

 liferous hairs more prominent than in 

 nature to show arrangement. (En- 

 larged.) (Original.) 



