Hesperoperla pacifica

Sandberg, John B., 2009, Vibrational Communication (Drumming) Of The Western Nearctic Stonefly Genus Hesperoperla (Plecoptera: Perlidae), Illiesia 5 (13), pp. 146-155 : 150-152

Hesperoperla pacifica – New Signal Character and

Additional Populations

The drumming of H. pacifica was examined from two additional populations in northern California (Table 2). Signals are reported separately for collected adults from Domingo Spring and reared adults from Domingo Spring and Butte Creek (Table 2). The male call of this species was first described as simple-monophasic (no grouped beats), by Stewart & Zeigler (1977). The call signals reported here are complex: 196 of 211 analyzed were composed of initial monophasic tapping (1–7 beats), followed by 5–15 grouped signals (from both sites and by collected and reared adults). For this reason the initial monophasic (♂ 1) and subsequent grouped portions (♂ 2) of the call were analyzed separately (Table 2). Figure 6A–C reflects the combination call pattern, with initial monophasic average interbeat intervals i1–i7, followed by the grouped portion with average intergroup intervals igi1–igi14. Overall intergroup intervals are reported only in Table 2.

Reared Butte Creek H. pacifica – One hundred twenty signals were recorded from three males (1–3 days old) and 25 signals from one female (1–5 days old) (Table 2). Ten signals were recorded and analyzed for the second female, collected live from Butte Creek that answered the audio playback of one previously recorded Butte Creek male call signal (Table 2). Male calls recorded 11–25 April 2007, had initial monophasic tapping with 2 mode beats (2.2 1.1) and overall average interbeat intervals of 213.1 65.3 msec, followed by 6–15 groups with 3 mode beats (2.6 0.7) and overall average intergroup intervals of 18.7 2.8 msec (Table 2). The 1–4 beat grouped signals had decreasing individual average intragroup intervals (19.7 2.8, 17.8 2.2, and 14.7 0.7 msec). Average male call durations were 4633 586 msec. Female answers had 31 mode beats (27.2 8.0) and overall average interbeat intervals of 83.7 17.7 msec. The male-female exchange patterns were 2-way (n=10) and 3-way (n=5) ( Fig. 3-A ) and their average durations were 2085 305 and 8654 564 msec respectively.

The average interbeat interval call pattern of reared Butte Creek males indicated by white bars decreased throughout the 1–8 beat (i1–i7) initial monophasic portion ( Fig. 6A ). In the following grouped portion, the average intergroup interval pattern changed at about midpoint (igi9). Average intergroup intervals decreased over the first nine groups (igi1–igi8), then increased only slightly in the remaining six groups (igi9–igi14) (with the exception of igi11 that decreased).

Field-collected Domingo Spring H. pacifica – Sixty-nine and 28 signals were recorded from five males and two females, respectively, on 19 May and 09 June 2007 (Table 2). Male calls recorded 19–20 May and 10–12 June, had initial monophasic tapping with 1 mode beat (1.6 0.7) and overall average interbeat intervals of 84.6 12.6 msec, followed by 5– 9 groups with 2 mode beats (2.0 0.3) and overall average intergroup intervals of 13.4 2.4 msec (Table 2). The 1–4 beat grouped signals had decreasing individual average intragroup intervals (13.5 2.5, 13.0 1.2, 11.8 (n=1) msec). Average male call durations were 661 155 msec. Female answers had 30 mode beats (26.7 9.7) and overall average interbeat intervals of 70.6 16.1 msec. The malefemale exchange patterns were 2-way (n=28) and 3- way (n=1) and their average durations were 2906 827 and 5271 (n=1) msec respectively.

The average interbeat interval call pattern of fieldcollected Domingo Spring H. pacifica indicated by gray bars decreased throughout the 1–4 beat (i1–i3) initial monophasic portion ( Fig. 6B ). For the following grouped portion (igi1–igi8), the average intergroup interval pattern was relatively constant, increasing throughout the 9 groups (except igi3, which decreased).

Reared Domingo Spring H. pacifica – Twenty-two signals were recorded from two males (3 days old) and 6 signals from two females (1–3 days old) (Table 2). Male calls recorded 16–18 June 2007, had initial monophasic tapping with 1 mode beat (1.7 0.7) and overall average interbeat intervals of 76.6 8.1 msec, followed by 5–8 grouped signals with 2 mode beats (1.9 0.3) and overall average intergroup intervals of 12.2 1.7 msec (Table 2 and Fig 4-A ). Average male call durations were 612 53 msec. Female answers had 12 mode beats (11.3 3.3) and overall average interbeat intervals of 46.6 14.7 msec. The malefemale exchange patterns were 2-way (n=6) and 3- way (n=2) ( Fig. 4-B ) and their average durations were 1205 113 and 3724 220 msec respectively.

The average interbeat interval call pattern of reared Domingo Spring H. pacifica indicated by black bars changed during the 1–4 beat (i1–i3) initial monophasic portion ( Fig. 6C ), first decreasing (i2) and then increasing slightly (i3). The following average intergroup interval pattern changed very slightly twice, first decreasing (igi1–igi3), then increasing (igi4–igi5), and finally decreasing again (igi6–igi7).

Figures

Fig. 6. Hesperoperla pacifica complex monophasic-grouped call patterns based upon individual average interbeat intervals i1-i7 and average inter-group intervals igi1-igi14 (msec) for one Butte Creek (BC) and two Domingo Spring (DS) 2007 analysis groups. A) White bars = BC reared male calls (N=120), B) Gray bars = DS collected male calls (N=69) and C) Black bars = DS reared male calls (N=22). Y-axis ranges from 50-250 msec.

Fig.3. Hesperoperla pacificadrumming.A. 3-way exchange, ♂Cmonophasicand grouped, ♀and ♂Rmonophasic answerand response respectively. B. Male call with 1st monophasic beat followed by 16 grouped signals. Reared from Butte Creek, Butte Co., CA, J. Sandberg, April 2007. d = (♀-♂R) exchange interval, e = inter-group interval, f = intra-group interval.

Fig. 4. Hesperoperla pacifica drumming. A. Male call with 1st, 2nd and 7th beats monophasic and the others grouped. B. 3-way exchange. Reared from Domingo Spring, Plumas Co., CA, J. Sandberg, June 2007.