3 oi8 THE JOINTED ANIMALS 



immemorial regarded it as something supernatural, and as foretelling various events 

 in the future, some looking upon it as a sign of the imminence of war, others of the 

 destruction of their crops, etc. The pupa of the army worm is shown at b in the 

 figure on p. 3017. This stage lasts from eight to twelve days; but the perfect 

 insect is short lived, the female surviving apparently only long enough to pair with 

 the male and lay her eggs. 



When speaking of one of the true midges reference was made to a pathological 

 case of phosphorescence, but in the present family there are two instances known 

 of the normal occurrence of this phenomenon not, however, in the adult insect, 

 but in the larval or pupal stages. The first instance is furnished by Ceroplatus 

 sesioides, a midge, which although not yet known to occur in England, has been 

 met with in several of the countries of Europe. Here the luminosity is said to re- 

 semble that of the glowworm, but proceeds from the entire animal, and from mem- 

 bers of both sexes. The larvae, which are found in small colonies on the under side 

 of a fungus, exhibit, when crawling in the dark, a moving streak of light, less 

 bright than that emitted by the pupae. The insect also shines when lying in the 

 cocoon, so long as its abdominal rings are still transparent and have not attained 

 their complete coloring. The cocoons themselves are not luminous, but allow the 

 light to be transmitted as through a paper lantern; and since as a rule several of 

 them are situated together a more extensive glow is displayed, whereby both the 

 cocoons themselves and the surrounding objects are illuminated. When the insect 

 is about to emerge from the cocoon, the luminosity gradually diminishes, and ulti- 

 mately ceases altogether. The second instance is presented by a New Zealand 

 midge called Boletophila luminosa, the larva of which is known as the ' ' glowworm." 

 Here the female is luminous in all three stages of its existence, but in the male the 

 luminosity disappears two or three days before the emergence of the perfect insect. 

 The luminous organ, which is situated in the posterior part of the body of the 

 larva, consists of, a gelatinous, semitransparent structure, capable of extension, 

 contraction, and other changes of form, and, like its luminosity, is completely under 

 the animal's control. As to the part played by this organ in the midge's economy, 

 authors'are at variance; one believing that the light serves to attract small creatures, 

 so that they become entangled in a web of mucus, which the larva suspends in 

 some niche in the soil. 



The gall midges (Cecidomyidai) are minute, fragile insects, in which 

 the wings are furnished with few veins, are often hairy, and always 

 fringed on the edges. From an agricultural point of view, these insects are the 

 most important of all the gnat-like flies, since much damage is at times done to 

 crops by their larvae. The most notorious is the Hessian fly (Cecidomyia dessauctor), 

 represented in its various stages in the following illustration. This insect was 

 believed to have been introduced into North America by the Hessian troops at the 

 time of the War of Independence, whence the inhabitants of the United States gave 

 it the name by which it is now commonly known. The adult female, which meas- 

 ures rather less than a tenth of an inch, is mostly of a velvety black color, varied 

 with blood red, especially on the abdomen; while the rather larger male is browner, 

 with the red clearer. These flies may be observed on the wing during the second 



