NOTES ON BUTTEKFLY VVPJB, ETC. 107 



4. Doritif!. — This mucli resembles Luehdorfia in form and appearance, 

 but has lost the creinastral liooks, as well as all power of movement ; 

 the pit of the pro-thoracic spiracle still appears, but is much less pro- 

 nounced, whilst the nose-horns are reduced to obsolescence. Tlie egg 

 is dome-sliaped as in Papilio. 



5. Parnnssius. — This is nearly identical with Dorifis, except that 

 the rough surface is replaced by a very smooth one, wliicli is covered by 

 a resinous bloom ; this gives it an extremely different aspect, and is 

 associated, no doubt, witli the habit of making a sti'ong, thougli loose 

 cocoon, often in moist situations. The ventral position of tlio head 

 indicates the thoracic pitting otherwise smoothed out. 



All these forms are evidently related, but they do not admit of being 

 arranged in a linear series. The earlier forms, at least, possess the 

 intersegmental sub-segment, whilst the head gradually assumes an 

 inferior position, almost as pronounced as in the Lycaanids. 



(To he continued.) 



gCIENTIFIC NOTES & OBSERVATIONS. 



Discussion ori the JSfatupe of certain Insect Colours. 



{Continued /rem p. 86 J 



I am exceedingly pleased that Mr. BurroAvs* has joined in this 

 discussion. His complaint that we have, in our discussion, got out of 

 the dejith of ordinary mortals is perhaps well deserved ; it is certainly 

 necessary, if our discussion is to be of any service, that everyone should 

 understand at what we are aiming, and Ave should be indebted to j\Ir. 

 BurroAvs for kindly hinting that Ave are sloAvly ascending to cloudland, 

 and asking us to explain more clearly Avhat it is that Ave want the 

 members to understand in less technical language. His own state- 

 ments are, indeed, a model of clearness. 



For a definition of terms our readers must of course go to an 

 elementary text-book on light, but it may be Avell here to explain a 

 little. Ordinary light is termed " white " light, and is made up of the 

 primary colours — red, orange, yellow, green, blue, indigo and violet, 

 each of these colours in fact representing the effect produced on the 

 optic nerve by the variable rate of A'ibration of the constituent Avaves of 

 which Avhite light is really composed. If the numlier of A'ibrations 

 produced by the light Avaves entering the eye be 474,439, ()80,00(j,000 per 

 second (each vibration producing a Avave l-39,00Uth of an incli in length), 

 then the impression produced is tliat of red colour ; if, however, the 

 number of A'ibrations of the light AvaA-es entering the eye be 

 H99, 494,400,000,000 per second (each Avave being 1-57,500 of an inch in 

 lengtli) then violet is produced ; the intermediate colours have inter- 

 mediate rates of A'ibration and hence intermediate AvaA^e-lengths. 



If a su])stance has the power of absorbing some of the light Avaves 

 from the Avhite light (all the colours combined) Avhich ordinarily falls tipon 

 it, and of reflecting others, only the reflected portion can ])Ossibly affect 

 the optic nerve. If the red rays only be reflectecl, then the colour of the sub- 

 stance appears to us to be red ; if blue, then the colour appears blue, and so 



* Tlie paper by Mr. BurroAvs, here referred to, has unavoidably to be jiostponed 



until the next issue. 



