HARDWICKE'S SCIENCE-GOSSIP. 



83 



WARNING ODOURS. 



T NSECTS which are protected by the possession of 

 ■A- a disagreeable taste, require in addition some 

 characteristic by which their enemies may easily and 

 at once recognise them. Without this, they would 

 be i liable to be killed in mistake for some eatable 

 species. In the case of day-flying insects, as butter- 

 flies, this warning is most readily given by a peculiar 

 system of coloration. In the case of nocturnal in- 

 sects this is not sufficient, and some other means 

 must be adopted. Four devices suggest themselves : 

 (1) a white or light coloration joined to a peculiar 

 flight, (2) actual emission of light, (3) a peculiar 

 noise, (4) a peculiar odour. As instances of the first 

 three ways, I may give as probable examples : (1) 

 Hepiahis humuli, (2) fireflies, (3) the moths I men- 

 tioned in my first letter to this paper, as making a 

 clicking noise. Unfortunately, the idea did not 

 occur to me in time to verify the actual possession of 

 a disagreeable taste in these instances. In the case 

 of the fourth class, insects possessing a warning odour, 

 there would obviously be an advantage in the odour 

 being itself repulsive. In this case, we, knowing 

 nothing of the taste, and perceiving the repulsive 

 odour, would naturally think that the disagreeable 

 nature of the odour was the protection, and overlook 

 its warning character altogether. This is, I think, 

 what has occurred in the case of the " flying bug " of 

 India. This insect has a very strong odour, which 

 most persons find exceedingly repulsive. When I 

 first arrived in India, I was told that the insects were 

 protected by their odour, and this seemed, on the 

 face of it, very probable. Subsequently, I noticed 

 that the smell was not quite the same in different 

 individuals ; this led me to observe it more carefully, 

 and I was surprised to find that the repulsion which I 

 at ifirst felt, very soon disappeared, and I began to 

 regard the smell as rather pleasant than otherwise. I 

 got a friend to try it, with the same result ; a resolute 

 effort was needed in the beginning, but after a couple 

 of hours the odour ceased to be disagreeable, and 

 never again became so. This led me to think that if 

 the insect was really protected by the smell, either 

 its disagreeableness was more persistent in the case 

 •of animals, or it was not nearly so effective as sup- 

 posed. One night one of these bugs flew into my 

 mouth, and I noticed that it had a strong, acrid, and 

 intensely disagreeable taste. This suggested to me 

 that the real protection might be in the taste, and 

 that the odour was merely a correlative variation, or 

 a slight additional protection ; the idea that it could 

 be warning did not occur to me then. To corroborate 

 this, I macerated a bug in sherry, and then tasted the 

 wine ; as I expected, it had a strong and very dis- 

 agreeable taste, and a tendency to cause nausea. I 

 also gave one to a tame lizard, which was accustomed 

 to take insects from the hand ; he seized it, but in- 

 stantly rejected it, and for some time afterwards, 



violently shook his head, as though to get rid of some 

 disagreeable impression. 



While stationed at Karwi, I noticed an interesting 

 fact connected with these bugs. During the rains 

 they flew into my bungalow in swarms ; I have seen 

 my bed literally black with them. Large numbers of 

 a large and handsome toad, of a yellow colour 

 speckled with red, also came into the bungalow. 

 The bugs appeared to be this toad's favourite food. 

 Nothing else would touch them, but this toad ap- 

 peared to eat nothing else, although there were 

 plenty of other insects. This suggests a question. 

 Was the protection valueless against this toad from 

 the beginning, and acquired as a defence against 

 other animals ? Or was it in the commencement 

 good against everything, and have the toads learned 

 to disregard it comparatively lately? 



J. R. Holt. 



NOTES ON NEW BOOKS. 



' / ^ HE Game Birds and Wild Fowl of the British 

 -I Islands, by Charles Dixon (London : Chap- 

 man and Hall). It is a short time since we had 

 the pleasure of noticing Mr. Dixon's delightful book 

 on " The Migrations of Birds." He is a most diligent 

 and enthusiastic writer on ornithology, and has 

 devoted the whole of his still young and intellectually 

 active life to this special subject. The work before 

 us is larger, bulkier, and fuller than its predecessor, 

 admirably printed on good paper, and abounding in 

 excellent and artistic illustrations. It is a volume 

 which ought to "catch on" to every sportsman- 

 naturalist. Most sportsmen are naturalists without 

 knowing it, although all naturalists are not necessarily 

 sportsmen. Mr. Dixon's book not only gives a 

 detailed account of all our native game birds and 

 wild fowl, but also of species allied to them in every 

 part of the world. It is the broadest in treatment 

 of any ornithological work we know of; admirably 

 written in good English, and deeply interesting to 

 read. It runs to 480 pp., which are divided into 

 the latest classified ornithological groups. There 

 is also a full and convenient index. A work like 

 this would be a veritable boon in a country house on a 

 rainy or snowy day. 



Extinct Monsters, by the Rev. II. N. Hutchinson, 

 B.A., F.G.S., etc. (London: Chapman and Hall). 

 To an old geological writer it is very delightful to 

 welcome a clergyman to the ranks of geological 

 literary scribes. It was so very different more than 

 thirty years ago. Then, geologists were expected to 

 expound " Genesis " to theologians, now theo- 

 logians expound very original views of " Genesis" to 

 geologists ! No doubt it will all come right in time. 

 Mr. Hutchinson broke his geological ground in the 

 columns of Science-Gossip three or four years ago, 

 and very naturally in verse ? But there was a 



