292 SUMMARY OF CURRENT RESEARCHES RELATING TO 



colour-patterns in 1173 species — 453 of Papilio, 30 of Ornithoptera, G43 

 Hesperidae, and 47 of Castnia. There are three sorts of markings upon 

 the wings of Lepidoptera : — spots, hands, and " combination-markings," 

 linear combinations of spots and bands. Some general " laws of varia- 

 tion" are stated, e.g. that departures from the normal are much more 

 apt to affect the ends than the middle of a marking ; like kinds of 

 markings are more apt to fuse than unlike, and so on. 



Mayer finds that Papilios belonging to different subgenera, and 

 living in widely separated parts of the world display a number of similai 

 peculiarities of colour-pattern. Some of these peculiarities are constant 

 among groups of Papilios which differ greatly in general appearance, 

 live in dissimilar environments, and are subject to the attacks of dis- 

 similar enemies. As some of these peculiarities are too insignificant to 

 affect the general appearance of the insects, and remain the same under 

 widely different conditions of selection and environment, they appear to 

 be due neither to natural selection nor to environmental influences. 

 They may, however, be due to a conservatism in heredity, or race- 

 tendency, which has remained constant in the majority of the species 

 despite the changes which time, selection, and all other causes have 

 produced. 



The characteristic differences between the species of a genus, or the 

 genera of a family, group themselves about certain dominant conditions, 

 most of these differences being only slight departures from the dominant 

 form. Each genus or family displays its own peculiar conditions, and 

 follows its own peculiar law of differentiation. On the whole this 

 research favours the theory that new species have often arisen by muta- 

 tion independent of environment and in many cases not interfered 

 with by adverse selection. This conclusion accords very well with what 

 De Vries has recently observed in the mutations of such plants as 

 CEnothera. 



Net-winged Midges.* — V. L. Kellogg notes that the net-winged 

 midges or Blepharoceridae have long been of peculiar interest to entomo- 

 logists because of the small number of known species and their supposed 

 rarity, because of the wide and discontinuous distribution, because of 

 the remarkable aquatic life of larvae and pupae, and the strarjge modifi- 

 cation of the body in both these stages in conformity with the curious 

 habits, and because of the unique pseudo-net-veining of the wings of 

 the imagines, produced by a series of folds in the wing membranes. 

 Kellogg has called attention to other interesting features, especially the 

 composition of the compound eyes of the imagines of two sizes of 

 ommatidia, with differences in disposition of the retinal pigment, &c, 

 resulting in a certain accommodation to different intensities of light. 

 In the present paper the author describes four new North American 

 species and their immature stages (which live submerged in swift clear 

 streams). He gives an account of some of the structural peculiarities of 

 both larvae and adults, e.g. the larval suckers and the imaginal eyes ; 

 and discusses the habits and life-history so far as these are known. A 



* Contributions from Hopkins Lab. Leland Stanford .Jr. Univ., No. xxx. Reprint 

 from l'roc. California Acad., 3rd set. (Zoology) lii. pp. 187-2J2 (.5 pis.). 



