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 described, repeated regularly, rhythmically, and monotonously 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, niveus. D, four-spotted tree cricket, nigricornis 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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