Animal Luminescence 539 



read at night in a dark place without a torch, provided one moves 

 the animal over it and conducts it slowly along the lines." Thus 

 the brightness of a luminous animal was measured by the ability to 

 read print in its presence at the beginning of the seventeenth cen- 

 tury, a comparison followed by observers of luminescence ever since. 

 Colonna also pointed out that " even after death, as long as there 

 is still moisture, the buttocks of the dead body shine in the dark, 

 but once they have become dry, the light goes out." 



Another book of the same period was the Historia Animalium 

 Sacra, etc., started by Wolfgang Franz (1564-1628) , a German protes- 

 tant theologian. It first appeared in 1612, with many subsequent 

 editions. In 1712 there were five parts, the last entitled " De Insec- 

 tis," by Joannes Cyprian, containing a section " Quidam ignito modo 

 lucent," which deals with fireflies and is especially valuable because 

 of the large number of Avriters on these insects referred to. 



In the 1659 edition, a section under Scarabaeus describes the 

 " Lampyrides seu Cicindelae shining in a strange manner with 

 something like a lucid moisture on their belly . . . they say that if 

 this fluid is mixed with others and used for writing it can be read at 

 night and not in the daytime." Franz then went on to point out 

 that " They resemble those [persons] who shine only as long as they 

 are in the dark, that is among uneducated people, for among the 

 educated they would be inconspicuous." 



At the beginning of the seventeenth century, accurate knowledge 

 of these insects was fairly well expressed by the statement of Francis 

 Bacon in his Sylva Sylvarum (1627, sec. 712) . 



The nature of the glow-worm is hitherto not well observed. Thus much 

 we see; that they breed chiefly in the hottest months of summer; and 

 that they breed not in champain [fields], but in bushes and hedges. 

 Whereby it may be conceived, that the spirit of them is very fine, and 

 not to be refined but by summer heats: and again, that by reason of 

 the fineness, it doth easily exhale. In Italy, and the hotter countries, 

 there is a fly they call Lucciole, that shineth as the glowworm doth; 

 and it may be is the flying glow-worm. But that fly is chiefly upon fens 

 and marshes. But yet the two former observations hold; for they are 

 not seen but in the heat of summer; and sedge, or other green of the 

 fens, give as good shade as bushes. It may be the glow-worms of the cold 

 countries ripen not so far as to be winged. 



It is probable that Bacon did not have many glowworms for 

 experimentation, as his treatment lacks the inquiring approach of 

 his remarks on luminous wood (see Chapter XIV) . The last sentence 

 is a definite suggestion that glowworms might develop into fireflies, 

 as indeed some species do, although the European glowworm, with 



