_Ontogeny of the Noctua larvæ._--References have already been given in a previous note (67, p. 166) to observations on the number of legs and geometer-like habits of certain _Noctua_-larvæ when newly hatched. This interesting fact in the development of these insects furnishes a most instructive application of the principle of ontogeny to the determination of the true affinities, _i.e._ the blood-relationship of certain groups of Lepidoptera. While the foregoing portions of this work have been in course of preparation for the press, some additional observations on this subject have been published, and I may take the present opportunity of pointing out their systematic bearing--not, indeed, with a view to settling definitively the positions of the groups in question, as our knowledge is still somewhat scanty--but with the object of stimulating further investigation. Mr. H. T. Stainton has lately recorded the fact that the young larva of _Triphæna Pronuba_ is a semi-looper (Ent. Mo. Mag. vol. xvii. p. 135); and in a recently published life-history of _Euclidia Glyphica_ (_Ibid._ p. 210) Mr. G. T. Porritt states that this caterpillar is a true looper when young, but becomes a semi-looper when adult. To these facts Mr. R. F. Logan adds (_Ibid._ p. 237) that “nearly all the larvæ of the _Trifidæ_ are semi-loopers when first hatched.” The _Cymatophoræ_ appear to be an exception, but Mr. Logan points out that this genus is altogether aberrant, and seems to be allied to the _Tortricidæ_. Summing up the results of these and the observations previously referred to, it will be seen that this developmental character has now been established in the case of species belonging to the following families of the section _Genuinæ_:--_Leucaniidæ_, _Apameidæ_, _Caradrinidæ_, _Noctuidæ_, _Orthosiidæ_, _Hadenidæ_, and _Xylinidæ_, as well as the other _Trifidæ_ (excepting _Cymatophora_).[215] The larvæ of the _Minores_ and _Quadrifidæ_ are as a rule semi-loopers when adult and may be true loopers when young, although further observations on this point are wanted. These facts point to the conclusion that the _Noctuæ_ as a whole are phyletically younger than the _Geometræ_, whilst the _Genuinæ_ and _Bombyciformes_ have further advanced in phyletic development than the _Minores_ and _Quadrifidæ_. The last two sections are therefore the most closely related to the _Geometræ_, as correctly shown by the arrangement given in Stainton’s “Manual;” whilst that adopted in Doubleday’s “Synonymic List,” where the _Geometræ_ precede the _Noctuæ_, is most probably erroneous.