512 THE INSECT WORLD. 



many days at the door. The snail puts off for as long a time as he 

 is able the fatal moment. But when, overcome by hunger or nearly 

 stifled in his prison, he decides at last to open the door, the Drilus 

 profits immediately by this opportunity, and cuts the muscle which 

 keeps back the foot of the snail. The breach being made, nothing 

 more opposes itself to the entrance of the enemy. He slips in, and 

 sets to work to eat at his leisure the unfortunate inoffensive mollusc, 

 which affords him board and lodging. The Ptilodactylides, the 

 Eucinetides, and the Cebrionides belong to the same family. The 

 first is exotic. 



The Elateridce are rather large insects, often of hard texture, 

 having the prosternum prolonged into a point (Figs. 551 and 552), 

 and the antennas indented saw-wise. They have the power of 

 jumping when placed on their backs, and of alighting again on their 

 legs. Hence their name of Elater (derived from the same root as 

 the word elastic). They produce, in leaping, one sharp rap, and often 

 knock many raps when they are prevented from projecting them- 

 selves. This is the mechanism which permits the skip-jack to execute 

 these movements. It bends itself upwards by resting on the ground 

 by its head and the extremity of the abdomen, and then it unbends 

 itself suddenly, like a spring. The point at the end of the thorax 

 penetrates into a hollow of the next ring ; the back then strikes with 

 force against the plane on which it rests, and the animal is projected 

 into the air. It repeats this manoeuvre till it finds itself on its belly, 

 for its legs are too short to allow of its turning over. Its structure 

 supplies it with the means and the strength of rebounding as many 

 times as it falls on its back, and it can thus raise itself more than 

 twelve times the length of its body. 



The larvae of the genus Elateridce (Fig. 553) are cylindrical, with 

 a scaly skin and very short legs. They live in rotten wood or in the 

 roots of plants.- According to M. Goureau, they pass five years in 

 this state. 



The larvae of the genus Agriotes occasion considerable damage to 

 wheat-fields. They have much resemblance to the meal-worm, or larva 

 of the Tenebrio. The Tetralobides are the largest of the Elateridcs, 

 attaining to a length of two inches ; and are inhabitants of Africa and 

 Australia. 



In America are found phosphorescent Elaterida. These are the 

 Pyrop/tori, which the Spaniards of South America call by the name 

 of Cncuyos. They have, at the base of their thorax, two small, 

 smooth, and brilliant spots, which sparkle during the night ; the 

 rings of the abdomen also emit a light. They give light sufficient to 



