10 



THE AGRICULTURAL NE\^^S. 



Jam AHV 1-2. 1918. 



INSECT NOTES. 



THE PRODUCTION OF LIGHT 

 CERTAIN ANIMALS. 



IN 



In the tirst pirt of the article which appeared in the 

 last number under this title, mention was made of some of 

 the animals which are capable of light protiuction, and 

 a short account was given of the habits of some of the 

 socillsd 'tire-Mies' or "glow-woims' belonging to the beetle 

 family Larapyridae, occuning in Kurope and America. 

 Before |)ioceeding to an account of the recent investigations 

 as to the source of light in certain luminous animal?, it raiy 

 be of interest to mention some of the luminous insects in 

 other parts of the world. 



Lefroy, in 'Indian Insects' gives an account of some 

 larval or imtuature lire-files belonging to the family Lamjiyr- 

 idae which abound in moist licalities of the forest areas in 

 India. The luminous patches are on the under side of the 

 hinder part of the body, as is the case in the adult-; of 

 European and American Lampyridae. Lefroy says; 'This 

 Inminoeity is very striking, a bright greenish white light 

 being emitted. The light is evidently under the control of 

 the in.sect and can be i|uickly produced, though on the cessa- 

 tion of stimulus it fades only slowly. . . . These insects 

 . are nocturnal, are dependent upon moist condition-, and feed 

 upon snails. A large specimen required at least si.v small 

 srails daily, and with sufficient moisture and enough snails 

 throve in captivity. The luminosity is not used in feeding; 

 the insect seizes a snail, curls over en its back with the snail 

 held in its legs, and slowly devours the muscular part, leaving 

 the alimentary canal. This has been observed fre^juently, 

 and the luminous organ is not functional. 



Lanipyrid beetles belonging to the genera Lcxiula and 

 Diajjhanes are stated to be ihe commonest light-producing 

 species in India, but it is not known whether these are the 

 adult fonns of the larvae mentioned above. Lefroy has 

 observed that in these beetles the maks have a larger 

 luminons area than the females, and are e.Ntremely bright 

 and vivid in some cases. 



We now comi- to the family J^lateridae or click-beetles, one 

 genus of which, /'prof/wnis, includes 8"nie of the most biil 

 liani luminous insects in existence. As mcntionidin the 

 first part of the article, the distribution of these beetles is 

 .confined, so far as i.t known, to the tropics of .America and 

 the West Intlies. Various .species of these beetles are i|uite 

 common in some of these islands for a few weeks during the 

 summer, but very little is known about their habits A 

 I'orto liican species, /'. luminoxKy, is known to be beneKclal, 

 as the larva feeds on white jjrubs or hard-back grubs in the 

 »i!garcatic> fields. Th.'.«e 'fire Hies' show a great diversity 

 in the position of the luminous organ.s at diHerent stages 

 ill the life of the in.sect. It is stated by Sharp that the 

 young I irva of /'. nonlilvrns ha.s a luminous area at the 

 •junction of the liead and thorax, while the older larva 

 has several luminous points along the sides of the body. 

 "The adults of some .species of J'yrypJioXMi have a promi- 



nent eye-like lamii on each side of the dorsal or Tipper 

 surface of the thorax, and a third luminous area on the 

 ventral or under side of the body at the junction of the 

 thorax and abdomen. 



Having t'Hiched upon the distribution and habits of 

 -ome of the luminous animals, I will now give a short 

 account of the structure of the luminous organs of certain 

 typical insects as worked out by s-'me investigators, and 

 of the researches on th origin of the light produced. The 

 whole subjf ct is somewhat complicate.! and technical, and 

 can only be dealt with here as simply tnd briefly as possible. 



Our knowledft of the structure of the luminous organs 

 of insects dates back some fifty years or so to the work of 

 Schultze, who worked on a species of Liaii^yrii, one of the 

 European 'glow- worms'. This investigator found that the 

 light-producing organ, situated in this insect near the 

 extremity of the abdomtn, consists of two layers, an external 

 layer which is lurainou.", and an inttrnal layer which is 

 non-luminous. These two layers are of about equal thick- 

 ness, are composed of different types "i cells, and are closely 

 associated with each other. They are -upplied with tracheae, 

 or air-tubes, and nerves similar to those in other parts of 

 the body, which branch throughout the luminous org in 

 between the cells. 



The luminous or^an of Pt/rop/ijiiis was studied by 

 Heinemann, who found that it was essentially similar in 

 structure to that of Lat/ipt/ris, but the chemical composition 

 was somewhat different. He concluded that the li^ht is the 

 result of a process of oxidation. 



The first important contribution to the study of the 

 physiology of the light-producing "rgans of luminous 

 animals was made I'v Dubois in France some thirty years 

 ago, and the subject has been furtlier investigated within 

 recent yeir- by E. X. Harvey in the Tnited States, and by 

 Dubois. The researches of Dubois and Harvey have shown 

 that in three different group- of animals, namely fireflies, 

 ostracod Crustacea, and molluscs, there are two distinct 

 chemical substances, in addition to water and oxygen which 

 are necessary for the production of light. It is considered 

 that one of these substances is the scjurce of the light, and 

 that the other substance assists in proilucing the light. These 

 two investigators as will be .shown, differ in their theories 

 as to which of the two substances is the actual source of 

 light. (>■ .euce, A'. .S., -Vol XLIV, N'os. 1 12;S, 1 UO, 1181.) 



These two substances were termed lucifeiin and 

 liicifei'isc by Dubois, who was 1 he rir.st to discover them 

 in 188-1 in the West Indian 'cucuUo' Pi/iopliorui noctilwuf. 

 A few years later he also found them in the lumino'u 

 mollusc, Pholai -hrti/lus. In tbec-'urse of his researches 

 he found that lueiferin is not destroyed by heat, is capable 

 of oxidation with light production, and can be prepared bv 

 extracting the luminous cells with hot water, which destroys 

 thi? luciferase and not the lucifirin. i >ubois also' found that 

 luciforiise has the properties of an ouzyine, ' and is cap- 

 able of acceleraticg the oxidation -'f the lueiferin, and 

 can be prepared by allowing an extract of luminnus 

 Cells to stand until the light disappears The lueiferin 

 is complelely oxidized and u.sed up, while the Inciferase 

 remains. Dubois made extracts of each of these two 

 subsiances separately iij solution by tie above processes, and 

 then was able to c,l,iain light by, mi.\i,ng the solutions of 

 lueiferin and luciferasn in the presence o: oxygen. . He con- 

 cluded therefore that lueiferin is the t'jurce of the light, and 

 that Inciferase acclcrataa the process of oxidation. 



Th(» recent researches of Harvey liiveled him to arrive at 

 (|uite different conclusions from thos-? formed by Dubois, 

 Harvey has worked with a >i'i\iihber "f luminons animals, 

 includiHg tire-tiles of both fainillt,«, and ostracoil Crustacea, 



