PROC. ENT. SOC. WASH., VOL. 23, NO. 8, NOVEMBER, 1921 181 



larval and prepupal location and moves slowly dorsally and 

 inwards, while, as this progresses the facets of the compound 

 adult and pupal eye become slowly and indistinctly visible close 

 to the head capsule and in approximately their normal adult 

 position, extending from the old eye about halfway up the side 

 of the head. 



This withdrawing of the eye is accompanied,- and followed, by 

 a gradual development of the pupa. The head capsule of the 

 prepupa wrinkles and changes its surface in conformation with 

 the new and somewhat differently shaped structure within. The 

 thorax lengthens and the legs lay stretched straight posteriorly. 

 The first abdominal segment is constricted giving the prepupa a 

 characteristic "waistlined" appearance. The abdomen as a 

 whole is somewhat contracted and shortened and the spiracles 

 of the prepupa are connected with those of the forming pupa by 

 whitish narrowing bands or tubes. 



The dissections of the prepupa during these critical changes 

 and the attempts made to remove the skin of the prepupa from 

 the pupa indicate that during the early formation of the new 

 stage the two skins are practically identical in the closeness of 

 their association and that the pupal skin is very delicate. 

 Indeed no attempts to separate the two skins are successful 

 until the contraction of the pupa has advanced considerably and 

 the insect has begun a natural separation, with the pupa con- 

 siderably resembling the adult in form. This complicates the 

 work by making all the observations on the early pupal develop- 

 ment indirect and dependent upon observations of the changes 

 denoted by the prepupal skin and contour and the association 

 of these changes with steps in pupal development. However, 

 since the same insect can be observed through the entire course 

 of its development and by removing the skin of the prepupa 

 when it has separated from the pupa, pupal areas can be con- 

 nected with prepupal areas, it is possible to understand to some 

 extent the development of the pupa by the effects it produced 

 upon the skin of the prepupa. As the pupa is formed and its 

 divisions become sufficiently distinct for interpretation through 

 the prepupal skin it is found that the pronotum of the adult is 

 formed below areas B and C of the prepupal prothorax (area C 

 lies above the anterior margin of the prescutum of the meso- 

 thorax of the adult but is empty and folded flat posteriorly, 

 probably due to the longitudinal lengthening of the prescutum 

 and the consequent withdrawing anteriorly of that portion of 

 the pronotum formed beneath). The prescutum is narrow, long, 

 medianly divided and extends cephalad from under area A, 

 mesothorax of prepupa. Scutum is formed under B, and the 

 latero-dorsal and supraalar discs of C (in a specimen of a pre- 

 pupa the skin of which was removed to disclose the pupa 

 beneath, scutum was transversely and longitudinally divided) 



