INSECTS 



wings vertically above the back and vibrates them sidewise 

 so rapidly that they are momentarily blurred with each 

 note. The sound is that treat, treat, treat, treat already de- 

 scribed, repeated regularly, rhythmically, and monoto- 

 nously all through the night. At the first of the season 

 there may be about 125 beats every minute, but later, on 

 hot nights, the strokes become more rapid and mount to 

 160 a minute. In the fall again the rate decreases on cool 

 evenings to perhaps a hundred. And finally, at the end of 

 the season, when the players are benumbed with cold, the 



Fig. 38. Distinguishing marks on the basal segments of the 



antennae of common species of tree crickets 



A, B, narrow-winged tree cricket, Oecanthus angustipennis. C • 



snowy tree cricket, nivcus. D, four-spotted tree cricket, nigri' 



cornis quadripunctatus. E, black-horned tree cricket, nigricornis- 



F, broad-winged tree cricket, latipennis 



notes become hoarse bleats repeated slowly and irregularly 

 as if produced with pain and difficulty. 



The several species of tree crickets belonging to the 

 genus Oecanthus are similar in appearance, though the 

 males differ somewhat in the width of the wings and some 

 species are more or less diffused with a brownish color. 

 But on their antennae most species bear distinctive marks 

 (Fig. 38) by which they may be easily identified. The 

 snowy cricket, for example, has a single oval spot of black 

 on the under side of each of the two basal antennal joints 

 (Fig. 38 C). Another, the narrow-winged tree cricket, has 



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