i8o INJURIOUS AND USEFUL INSECTS 



lens two clear oval spots, one on the outer face and a smaller 

 one on the inner ; these are believed to be organs of hearing. 

 From the extremity of the abdomen project a pair of long, 

 tapering cerci, which have been compared to caudal antennae ; 

 they are well furnished with nerves and peculiar sense organs, 

 so that they have really some analogy with antennas, and 

 are probably employed in the same way. 



The head may be prepared and examined according to 

 the instructions given in Lessons 2 and 3. Note the large 

 sockets for the antennae, the degenerate eye-spots, the com- 

 pound eyes, relatively smaller than in the cockroach, the 

 powerful mandibles, and the maxillae and labium, much like 

 those of the cockroach. 



If, as generally happens, immature crickets are taken 

 among the rest, look out for wingless and imperfectly winged 

 individuals ; though the wings may be so short as not to 

 reach beyond the first abdominal segment, they will exhibit 

 a pattern not unlike that of the future functional wing. 



The fore wing of the male cricket is very different from 

 that of the female, and should be carefully examined. It 

 must be flattened out, and compared with a female fore 

 wing similarly treated. Notice the region internal to the 

 angle, along which the wing is longitudinally folded; it is 

 comparatively free from veins. Turn up the under side of 

 the wing, and about a third of the length from the fore 

 end look for a strong vein curving backwards towards the 

 base of the wing; along this a file is developed, and it is 

 by rubbing this file against the corresponding part of the 

 other fore wing that the chirping sound is produced. It is 

 possible to elicit a faint sound from a dead cricket, by rubbing 

 one wing against another. The adjoining clear spaces of 

 the wing take up the vibration, and themselves begin to 

 vibrate. It is probable that each picks out and reinforces 

 a single note, and that the chirp is a mixture of all these 

 notes. Contrary to the rule in Orthoptera, the right fore 

 wing of a cricket overlies the left, when at rest, but occasionally 

 it is the left which overlies the right. Perhaps the insect 

 can change the less efficient for the more efficient file, when- 

 ever this may be requisite. 



An organ of sound-production implies an organ of hearing, 

 and this is possessed by both male and female crickets. On 



