OF WASHINGTON, VOLUME XVII, 1915 47 



pupae did we have any suspicion that they would Drove to be 

 anything but normal alate insects. Yet in several cases the 

 adults were intermediate. 



Upon becoming adult, however, the intermediate, at a casual 

 glance, appeared to be apterous. In fact, it required close exami- 

 nation with a hand lens to perceive that it was not. The darker 

 color of the head and thorax was lost, and instead of being black, 

 as in the normal alate, it was of a uniform green with the ab- 

 domen, as in the apterous forms. Moreover, the shoulder of 

 the mesothorax tended to flatten out, approaching the more 

 uniform line of the apterous adult. 



In the true alates, the wing venation was found to grade from 

 the most complete nearly to the most reduced type known in 

 aphids. (Exception should be made of one or two species re- 

 cently described in which all veins, except those forming the 

 stigma have been eliminated) (figs. b-d). The great majority 

 possessed the most complete type, while only a small minority 

 had the more specialized venation. The wings of intermediates 

 which approached most nearly to the alate conditions were pro- 

 vided with even fewer veins, if they could be called such, than 

 were any of the normal alate insects (fig. e). They were usually 

 smaller than the wing pads of the pupae, approximating the pads 

 of third instar. This character varied greatly, however, form- 

 ing with the character of the venation, a nicely graded series 

 between the alate and apterous condition (figs. /-&). 



It is to be expected, if the wing condition of these intermedi- 

 ates were a true reduction and not a mere accidental abortion, 

 that it would be accompanied by a corresponding degeneration 

 in the alary muscles. Such is found to be the case. In all of 

 the specimens figured in the plate both pairs of dorso-ventral 

 and longitudinal muscles were reduced nearly to the apterous 

 condition. In specimen No. 1041, the form most nearly ap- 

 proaching the alate in wing condition, the large dorso-ventral 

 muscles were reduced but little. In No. 910, which closely ap- 

 proximates the apterous form, these muscles were found to be 

 almost exactly as in the apterous condition. In the intervening 

 forms they were reduced almost to the apterous condition, being 

 slightly larger in No. 999 than in the others. 



While the antennal measurements vary considerably in the 

 intermediate form, there is no appreciable difference in the aver- 

 age measurements of three adult types, nor does there appear 

 to be a greater variation within the intermediate than is found 

 within the apterous and alate forms. This is true, also, of the 

 measurements of the cornicles and posterior tibia-. 



The variation in one antennal character, however, well shows 

 the intermediate condition of our new form. No sensoria are 



