Eneoptera surinamensis (De Geer, 1773)

The teeth of stridulatory file are arranged linearly and inclined from the outer to the inner side of the tegmen (Fig. 1). Each tooth is shell-shaped (Figs. 2, 3); the larger ones are distributed in the medium region of the file, with a gradual reduction in size towards the extremities.

The smaller teeth located at the outer (Fig. 4) and inner (Fig. 5) ends of the file show an asymmetric morphology, irregular alignment and intermittent distribution. Parallel to the anterior side of the file occurs a dense accumulation of microtrichias, forming a strip that is broadest where the biggest teeth are located (Figs. 1, 4, 5). There is a gradual reduction in the accumulation of microtrichias following the decrease in teeth size towards the file endings. There are no microtrichias where the smaller, asymmetric and intermittent teeth are located (Figs. 2, 3).

Close to the outer end of the file (postcubital area) there is a hair plate (Fig. 1).

Specimens from Foz do Iguaçu have a file with 82 ± 9.8 teeth, including the minor and asymmetric ones, with the length of the file equal to 1.89 mm ± 0.15, which is equivalent to 43.76 ± 5.94 teeth per mm. The population from Rio Claro presents a file with 87 ± 9.81 teeth, with 1.96 ± 0.19 mm of length, and 44.52 ± 4.61 teeth per mm. Statistical test had disclosed that the differences found between the two populations are not significant (p>0,05).

The specimens from both places had been observed stridulating during the first hours of the morning, at nightfall and during the night. The calling song is a trill that alternates two distinct sets of notes, one of them (section a) with 0.6 s and the other one (section b) with 1.4 s (Fig. 6).

The section a includes 46 ± 3.74 (42 - 52, n=5) notes, each note with a duration of 0.009 s; the elapsed time between notes is 0.004 s (Fig. 7). The section b includes 80.8 ± 2.79 (77 - 85, n = 6) notes, with 0.012 s and the elapsed time between them of 0.007 s (Fig. 8).

In the section a, each note is composed of 24 pulses and in the section b, of 31 pulses (Figs. 9, 10, respectively). The minimum frequency of the calling song of specimens from Foz do Iguaçu is 2,706.7 ± 97.9 Hz (2497 – 2756, n=7) and the maximum frequency is 3,284.1 ± 153.5 Hz (3,014 – 3,445, n=7).

The minimum frequency of the specimen from Rio Claro is 2,325 Hz and the maximum frequency is 3,186 Hz. [1]

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