PROC. ENT. SOC. WASH., VOL. 23, NO. 8, NOVEMBER, 1921 189 



tg tegula. 



U urite abdominal segment. 



upd uropod leg. of abdominal segment (proleg). 



w wing. 



EXPLANATION OF PLATES. 



Plate XIV Larval Structure. 



fig. 1 Pteronidea ribesii Scopoli; larva; skin from interior, showing folds; 

 head, prothorax and mesothorax. 



fig. 2 P. ribesii; larva; skin from interior, showing folds; mesothorax, 

 metathorax and first abdominal segment. 



fig. 3 P. ribesii; larva; skin from interior, showing folds and muscles; 

 mesothorax, metathorax and first abdominal segment. The only 

 muscles indicated on the drawing of the mesothoracic tergum are 

 small, short, close to the body wall, attached to infoldings defining 

 the subdivisions of the segment and always attached within the 

 limits of the segment. Those indicated in the metathorax are only 

 the large segmental and intersegmental muscles. The first urite 

 shows muscles of all three types in the one segment. 



fig. 4 Neodiprion lecontei; larva; skin from the interior, showing folds; 

 mesothorax, metathorax and first abdominal segment. 



fig. 5 Pteronidea ribesii; larva; skin from the interior showing folds; third 

 and fourth abdominal segments. 



fig. 6 Pteronidea ribesii; larva; skin from the interior, showing folds; seventh 

 eighth, ninth aad tenth abdominal segments. 



fig. 7 Cimbex americana; larva; skin from interior, showing folds; meso- 

 thorax, metathorax and third abdominal segment. 



fig. 8 Arge salicis; larva; skin from interior, showing folds (area D exten- 

 ded); mesothorax, metathorax and third abdominal segment. 

 Plate XV Metamorphosis and Adult Structure of Pteronidea ribesii. 



fig. 9 Larva; from exterior; head, prothorax, mesothorax, metathorax and 

 first abdominal segment. 



fig. 10 Early prepupa; from exterior; head, prothorax, mesothorax, meta- 

 thorax and first abdominal segment. 



fig. U Prepupa in first stages of transformation to pupa (eye spot moving 

 and compound eye just discernible as forming); head, prothorax, 

 mesothorax, metathorax and first abdominal segment. 



fig. 12 Same prepupa (as figure 11) two days later; head, prothorax, meso- 

 thorax, metathorax and first abdominal segment. 



fig. 13 Prepupa, transformation to pupa advanced; head, prothorax, meso- 

 thorax, metathorax and first abdominal segment. 



fig. 14 Same prepupa (as figure 13) one day later; head, prothorax, meso- 

 thorax, metathorax and first abdominal segment. (Note: Wing 

 forming in mesothorax). 



fig. 15 Same prepupa (as figure 14) one day later; head, prothorax, meso- 

 thorax, metathorax and first abdominal segment. (Dorsal viewK 



fig. 16 Same prepupa (as figure 15) one day later. Skin partially removed; 

 head, prothorax, mesothorax, and metathorax. (Dorsal view.) 



