282 



NATURE 



[Feb, 7, 1878 



Electrical Experiment 



A FRIEND of mine has called my attention to a letter of F. T. 

 Pirani, of Melbourne, accompanied by some remarks of Prof. 

 J. C. Maxwell, in Nature, vol. xvii. p. 180. 



Mr. Pirani concludes his letter with the words, " If the 

 phenomenon (described in the letter) has not been noticed before, 

 I shall be obliged to you if you will kindly communicate it to 

 Nature." 



I take the liberty to request you to call, by means of your 

 esteemed journal, the attention of the author to an article of 

 mine, published in the late Prof. Poggendorfif's Annalen der 

 Physik (vol. clvii., 1876), an abstract of which appeared in the 

 Philosophical Magazine (5 ser. vol. i.). The phenomenon 

 alluded to in Mr. Pirani's letter, i.e. the existence of an electro- 

 motive force due to gravity, in a vertical column of an electrolyte, 

 is, I believe, fully pioved by the experiments described in the 

 article. The same difficulties met with by Mr. Pirani and Prof, 

 Maxwell, who repeated the experiment, that is, the presence of 

 irregular, casual currents, due to bubbles of air, &c., have also 

 been encountered by me ; I intimate the means of getting rid, to 

 a certain extent, of this influence. 



The transport of metal in one direction being accompanied by 

 a transport of the other ion in the opposite direction, the phe- 

 nomenon is more complete than it might appear at first sight, 

 and the electromotive force changes its sign according to the 

 electrolyte employed, R. Colley 



Kasan, Russia, January 23 



Oriental Affinities in the Ethiopian Insect-Fauna 



Many naturalists have already drawn attention to the Indian 

 affinities in the African fauna ; in other words, the zoological 

 relationship between the Oriental and Ethiopian regions. The 

 late Dr. Stoliczka has pointed this out in the Malayan ornitho- 

 logy ; Mr. Wallace has described the same thing in the mam- 

 malia and birds of West Africa, these possessing ' ' a special 

 Oriental or even Malayan element." He has also drawn atten- 

 tion to the Oriental element in the Ethiopian reptiles and am- 

 phibia, and to the many cases of the same in the South African 

 fauna. Mr. Blandford has treated of the '* African element in 

 the fauna of India," more particularly as regards the mammalia; 

 and the late Mr. Blyth has shown the ancient date of this rela- 

 tionship from the evidence afforded by the Siwalik deposits. 

 Mr. Murray has even inclined to the opinion that the Indo- 

 Malayan region should be included with that of Africa, south of 

 the Sahara, 



The " Insecta " of the Ethiopian region also shows the same 

 Oriental relationship, which seems to have hitherto received less 

 attention. Dr. Stoliczka has described this in the "Indian 

 Arachnoidea," and Mr. A. Murray in the coleoptera of which 

 he has given the names of eleven genera common to the two 

 regions. 



The same thing may be seen in the Lepidoptera and Hemip- 

 tera, of which I can only treat briefly, hoping to deal with the 

 subject in a more exhaustive and analytical form when possessed 

 of adequate data, which at present do not exist. 



Of the Lepidoptera a few specific examples will perhaps serve 

 the purpose better than the names of the many genera that 

 could be adduced. In the Rhopalocera : — Danais chrysippus, 

 Melanilis leda, Atella phalanta, Hypanis ilithyia, Lycatia teli- 

 canus, Idmais phisadia, and Callosune xiance, all belong to the 

 two regions, and with the exception of C. datia and /. phisadia, 

 have been all recorded from Madagascar. However, D. chry- 

 sippus (Greece and Turkey), II. ilithyia (Nubia, Abyssinia, and 

 Arabia), and Z. telicanus (Egypt and Arabia), would seem to 

 show from those habitats their route of migration from one region 

 to the other. In the Heterocera two examples must sufiice, and 

 may be accepted as typical of what probably occurs to a far 

 greater extent among the large number of African moths still 

 unknown to science. Plusia verlicillata and Patula macrops 

 have a wide range over the two areas. 



In the African Hemiptera-Heteroptera the Oriental relation- 

 ship is very pronounced. The following are some of the genera 

 common to the two regions : — Solenosthedium, Hotea, Coptosoma, 

 Brachyplatys, Piataspis, Canthecona, Agonoscelis, Antestia,,Bathy- 

 ccelia, Catacanlhus, Tessero-toma, Aspongopus, Phyllocephala, 

 Macrina, Mictis, Leptoglossus, Odonfoptis, Physopelta, Lestomerus, 

 Catami'arus, Pachynomus, Acanthaspis, Oncocephahis, and Tho- 

 delnms. Genera, of course, are subject to constant revision 

 and redivision, making, as a rule, generic calculations of geo- 



graphical distribution very uncertain and unstable. A genus of 

 to-day may embrace species belonging to two regions ; to-morrow 

 an author may split this genus into two, for which he may find 

 local characters. In other words, genera common to two regions 

 at the present time may be shown as the contrary by a later 

 worker. In a general way the value of the term genus is often 

 equal to the value of the term species. The twenty-four genera 

 of Hemiptera, however, which I have enumerated above, may 

 be accepted as more certain examples. Dr. Stil has paid par- 

 ticular attention to this order, and has made many genera from 

 a minute examination of structure, and I think his divisions 

 must at least be considered as sufficiently exhaustive. I have 

 carefully compared my list with his latest classification, and find 

 that eighteen out of the twenty-four genera still remain intact 

 on his catalogue, one other is common to the two regions from 

 an East African species I recently described, and so only five 

 remain, which Dr. Stal has further subdivided. Of these 

 twenty-four genera, twenty-two extend to the West African sub- 

 region, twelve have at the present time also been recorded from 

 China, and twelve from the Australian region. When v/e further 

 analyse the list as to the probable route of migration, it is found 

 that eight genera appear in Madagascar and two in Reunion ; 

 whilst a northern junction is also indicated by one genus 

 being found in Tangier and Syria, two in Egypt, and one in 

 Abyssinia. A few species are common to the two regions, as 

 Leptoglossus membrCinanceus, Oncocephalus annulipes, &c. 



It is probable that the African Neuroptera and Orthoptera 

 may show the same affinities. W, L, Distant 



Derwent Grove, East Dulwich 



Sense in Insects — Drowned by a Devil-Fish 



In the file of Nature from October 18 to the end of Novem- 

 ber which I have just received, I find a discussion regarding the 

 senses possessed by insects, especially the lepidoptera. For 

 years I have been in the habit of collecting these insects for my 

 friends, and of course have become more or less acquainted with 

 their habits. I recall one or two instances in point. In Costa 

 Rica the Heliconias frequent certain flowers, and pass over 

 others of the same colour and same approximate size without 

 noticing them. But the most marked case was of the large bril- 

 liant Morphos. My Indian servants always carried with them 

 a fermented paste of maize flour, which they mixed with water 

 to the consistency of gruel as a beverage. On our arriving at 

 the side of a stream in a narrow gorge, invariably, within a few 

 minutes after they opened a package of this paste, although 

 there might not have been a butterfly in sight before, those most 

 brilliant of their kind would come sailing up, always from lee- 

 ward, and I have made some of my best catches in this manner. 

 I have also caught them by baiting with a piece of over-ripe or 

 even rotting banana. At other times they were almost unap- 

 proachable. They seem to live on fruits j ust merging into the 

 state of rottenness. 



I have never been able to detect any sensitiveness to sound in 

 insects, and suspect that the case cited by one of your cor- 

 respondents might be equally explained by sight, or by the 

 vibration of the air caused by striking the glass. That certain 

 coleoptera and diptera are attracted by smell alone is too obvious 

 to require proof. 



The same may be said of ants in following an established 

 trail. I have experimented with this frequently, obliterating the 

 scent for a space of but a few inches ; and watching the puzzled 

 wanderers each going an inch or less beyond his predecessor, 

 hunting the lost clue until the blank was finally bridged over. 

 After that if the new route as re-opened differed from the old, it 

 was nevertheless rigidly followed even if longer and less direct. 



Another matter. You mention a case of "drowning by a devil- 

 fish" (Nature, vol, xvii. p. 27). The story is to me very 

 probable. I once measured a specimen of my Octopus pimctatus 

 caught in San Francisco harbour, which gave clear 15 feet from 

 point to point of the arms. Tlie animal, as I bought it from a 

 fisherman, filled a champagne basket. W. M. Gabb 



Puerto Plata, Sto, Domingo, December 29, 1877 



Drowned by a Devil Fish 



Though in British Columbia at the time 01 the occurrence of 

 the incident referred to . by Mr. Moseley in Nature (vol. xvii. 

 p. 27) I was in the interior, and consequently heard nothing of 

 the matter. On reading Mr. Moseley's letter, however, I wrote 



