35*2 INSECTA. 



concealed under the thorax ; eyes of the males large and globular ; mouth 

 small. Such are the characters of a first division of this tribe, which we will 

 subdivide into those in which neither sex is phosphorescent, and those in 

 which the females at least are possessed of that faculty. Both sexes of the 

 former are provided with wings, have their head exposed, and frequently 

 narrower and extended anteriorly, or in the form of a snout, and the thorax 

 widened posteriorly with pointed lateral angles. The two or three ultimate 

 annuli of their abdomen are destitute of that pale yellowish or whitish tint, 

 that is always found on this part of the body in the true Lampyrides, and 

 which announces their phosphorescence. The elytra, in several, widen behind, 

 and are sometimes strongly dilated and rounded posteriorly, in the females 

 particularly. They are densely punctured, and frequently reticulated. 



The genera are Lycus, Dictyoptera, and Omalisus. 



The other Lampyrides of our first division are distinguished from the 

 preceding ones, not only by the want of a snout, by their head, which, in the 

 males almost entirely occupied by the eyes, is entirely or for the greater part 

 concealed under a semicircular or square thorax, but also by a very remarkable 

 character, either common to both sexes, or peculiar to the females, that of 

 being phosphorescent, whence the names of Glow-worms, Fire-flies, &c., 

 given to these insects. 



Their body is extremely soft, the abdomen particularly, which has the 

 appearance of being plaited. The luminous matter occupies the inferior part 

 of the last two or three annuli, which differ in colour from the rest, and are 

 usually yellowish or whitish. The light they diffuse is more or less vivid, and 

 greenish or whitish, like that of the different kinds of phosphorus. It seems 

 that they can vary its action at pleasure, a fact particularly observable when 

 they are seized or held in the hand. They live a long time in vacuum and in 

 different gases, the nitrous acid, muriatic and sulphurous gases excepted, in 

 which they soon expire. Placed in hydrogen gas, they, sometimes at least, 

 detonate. They continue to live after the excision of the luminous portion of 

 their abdomen, and the part thus separated preserves its luminous property 

 for some time, whether it be submitted to the action of various gases, be 

 placed in vacuum, or left exposed to the air. The phosphorescence depends 

 on the softness of the matter, rather than on the life of the animal. When 

 apparently extinct it may be reproduced by softening the matter with water. 

 The Lampyrides emit a brilliant light when immersed in warm water, but in 

 cold water it becomes extinguished : this fluid seems to be the only dissolving 

 agent of the phosphoric matter. They are nocturnal insects. 



In our second division of the Lampyrides, the antennae are very remote at 

 base; the head is neither prolonged nor narrowed anteriorly in the form of a 

 snout, and the eyes are of an ordinary size in both sexes. 



This division consists of the genera Drilus, Te'ephorus, Silis, &c. 



In the third tribe of the Malacodermi, or the MELYRIDES, we find the palpi 

 most commonly short and filiform ; mandibles emarginated at the point ; the 

 body usually narrow and elongated ; the head only covered at base by a flat or 



