44 



further material. On her return to Europe after several years*^ 

 residence there, she published her celebrated book " Dissertatio 

 Insectorum Surinamensium" (1719.) Here she figures the various 

 insects dealt with in the different stages of their life-history, together 

 with their foodplants and their parasites. 



I give you these details to show that the lady was, for her time, 

 a person with a very considerable knowledge of her subject, and her 

 word is not to be lightly disregarded. We may, therefore, believe 

 that she saw what she describes, although a possibility remains that 

 she may have seen and be drawing upon Master Grew's account of 

 the same insect. Almost certainly, however, her story is perfectly 

 bona fide evidence, yet many qualified naturalists have vainly sought 

 to confirm her statement. It seems certain that in the ordinary 

 way these insects are not luminous. In certain circumstances they 

 may normally become so, or they may become so in a diseased con- 

 dition. Mr. Distant has suggested* that the presence in their bodies 

 of luminous bacteria in large numbers may be the cause of the 

 phenomenon. The luminescence of certain Crustacea {Talitrns) 

 has been proved to be due to such pathologic reasons, as has that of 

 certain midges ; and the absence of any definite light-organ in these 

 lantern-flies seems to confirm the theory that the light must be due 

 to some e.rtra -normal conditions. Kirby and Spence mention the 

 case of a mole-cricket, which was taken to be a will-o'-the-wisp, and 

 chased and eventually captured, and its identity established. This 

 at once opens up another question that is rather shrouded in 

 mysteiy, viz., how far the peculiarly elusive light sometimes observed 

 over wet marshy ground, and going by the name of will-o'-the-wisp, 

 jack-o'-lantern, or l;/nisfatitiis, is due to mole-crickets or other bac- 

 terially luminous insects. I do not propose to enter now into a 

 discussion on this subject, but it certainly seems to be one worthy 

 of investigation by entomologists. Luminosity in the midges has 

 been reported on several occasions, chiefly from Eastern Europe. 

 The species concerned are Cliirononnts pluiiiosiis and C. temletis, and 

 the luminosity, which is sometimes very bright, embraces the whole 

 body and its appendages, and is entirely independent of the will of 

 the insect, persisting for some tune after death, even in alcohol. 

 The insects exhibitmg the light are always in a moribund condition, 

 sitting upon the bushes, from which if shaken they merely drop to 

 the ground unable to fly. It is supposed that this is a case 

 analogous to that of the amphipod crustacean Taiitnis, which is 

 sometimes found to exhibit a similar kind of luminosity. In this 

 case the body of the infected animal has been found to be swarming 

 with bacteria, which are the actual source of the luminescence. 

 Search has been made for bacteria in the luminous Chinmomns, but 

 in no case was the material sufficiently well preserved for bacteria 

 to be recognizable. In " Ent. Mo. xMag.," 1885-6, vol. 22, p. 266, 



* Distant, " Trans. Ent. Soc," 1895, p. 429. 



