xxxiii, '22] ENTOMOLOGICAL NEWS 49 



was shown that, in the very earliest stages, Rs lay in its normal 

 position below R, without crossing M at all. At a somewhat 

 later stage, Rs was shown crossing Ml only. Later still, Rs 

 was shown crossing both Ml and M2. 



If these drawings represent the correct postion of Rs, they 

 do most certainly constitute a strong argument for Needham's 

 view. Quite apart from the difficult question as to the actual 

 possibility of both a vein and its precedent trachea shifting its 

 position in this manner, it must be admitted that, if the larval 

 wing shows the ontogenetic stages in correct order, it would 

 be very difficult to avoid the conclusion that we were really 

 dealing with the original trachea Rs in this case. 



Now, I have repeatedly attempted to parallel these figures of 

 Needham's, by dissecting off the earliest stages of the larval 

 wings in various Anisopterous genera ; but I have never suc- 

 ceeded in finding any other condition than that in which the 

 supposed Rs crosses both .1/1 and M2, as it does in the last 

 larval in star. The genera examined by me were Aeschna, 

 Hcmicordulia and Diplacodes. Dr. Ris has also examined the 

 earliest stages of the larval wing in Libellula, and his results 

 agree exactly with my own. One of his photographs shows 

 such an early stage of the growth of the larval wing that the 

 extreme length of it is barely half the breadth at the base; yet. 

 in this case, as in the corresponding stages of those genera 

 which I have examined, the supposed Rs descends almost trans- 

 versely across the wing, crossing both Ml and M2, as in the 

 last larval instar. 



There were, therefore, only two possible conclusions to come 

 to. Either the genus GouiMnis presents a more complete onto- 

 genetic series of the development of Rs than do the other 

 genera studied, or Needham's drawings were incorrect. 



Recently, during my tour round the world, I visited Ithaca 

 and met Professor Needham. Together we collected larvae 

 of Complins and Ha/jcnius in the creek there, and I decided 

 to dissect the wings of the earliest stages obtainable, and com- 

 pare them with Needham's own drawings. I must admit that 

 the result came as a great surprise. Text-fig. 3 shows the con- 

 dition in the two earliest obtainable instars. The instar shown 



