Chromosome Behaviour and Phylogeny in the Neuroptera

Abstract

THERE has been disagreement on morphological and palæontological grounds as to the relationship of the groups of true Neuroptera and Megaloptera. In the first place, take the family Sisyridse of the true Neuroptera (or Planipennia). Its members possess aquatic larvæ, and as they have some morphological features in common with Osmylidæ, the larvæ of which are semi-aquatic, Tillyard¹ in 1916 put forward the suggestion that it had to be regarded as a comparatively late offshoot of the latter. This view was then adopted by Withycombe², and recently Killington³ in his admirable monograph of the British Neuroptera maintains the idea that ” these two families are no doubt closely allied, and, indeed, it appears very probable that the Sisyridae have been derived from an Osmyloid ancestor”. On the other hand, Handlirsch⁴ was not of the opinion that the families were very nearly related, and pointed out that Sisyridae show a remarkable similarity with the then oldest known fossil remnants of true Neuroptera, that is, the Triassic Prohemerobidae, the larvae of which are supposed to have been aquatic also. Recently, Handlirsch⁵ (and Beier), after having considered the discoveries of true Neuroptera in the Permian by Tillyard⁶ and Martynov⁷, also directs attention to the striking resemblance of some of these very old remnants with the living Sisyridae, which group he stil] regards as a primitive and primarily aquatic one. Tillyard⁸ seems later to have given up his original view and regarded Sisyridae as ” a specialized side branch” not very close to Osmylidae. After much dispute, therefore, morphologists have come to no agreement on the relationships of the two groups.