732 INSECTS AHUOAD. 



years Locust. It has gained this name from its ahnost regular 

 recurrence in the same spot once in every seventeen years. It 

 does not appear and disappear simultaneously over the whole 

 country, but takes one district at a time, appearing in vast 

 swarms, doing great damage for a season, and then vanishing 

 until the time for its next periodical visit. In some places its 

 teim of re-appearance is thirteen years. 



Its colour is green, and the wings are edged with brown. 



Another example of the Cicadas is given on Plate XVIII. 

 Fig. 1, where Cicada adusta is mentioned. I very much regret 

 that want of space debars me from inserting a long and very 

 interesting account of the habits of certain species of Cicada, 

 which I had preserved for this work. Suffice it to say that 

 they are tree-feeders, and that the males are remarkable for the 

 loud shrilling noise which they produce by means of an appa- 

 ratus called the " drum," Mdiich is placed in the under side of 

 the thorax, and is covered with a horny plate that can mostly 

 be seen from the upper surface of the insect. 



The present species is a native of Siam and Java, and is 

 rather variable. Being a very large insect, the figure is neces- 

 sarily reduced one-half. In some specimens the wings are 

 wholly translucent, as shown in the illustration, and in others 

 they are spotted wnth brown at the intersections of tlie nerviu^es. 

 Their whole surface is extremely iridescent. 



The remarkable insect called Cystosoma Saundersii is a 

 native of Australia, and is a singular example of imitation, 

 being almost exactly like the Cystocoelia which has been de- 

 scribed on page 342. 



In this insect the abdomen of the male is extremely large, 

 and quite hollow, the vital portions only occupying a slight 

 streak of thicker substance on the lower surface of the abdomen. 

 The horny cover of the ''drum," to which reference has been 

 made, is seen just at the base of the lower wings. The object 

 of this singular structure is uncertain, but some entomologists 

 think that the hollow abdomen may increase the resonance of 

 the sound produced by the drums. 



The female has a much smaller abdomen, but it is solid aiid 

 opaque, whereas that of the male is quite translucent. The 



