Acanthagrion speculum Garrison, 1985

Román-Heracleo, Jareth, Springer, Monika & Novelo-Gutiérrez, Rodolfo, 2019, Descriptions of the larvae of Acanthagrion speculum and A. trilobatum from Costa Rica (Odonata: Coenagrionidae), Zootaxa 4624 (2), pp. 219-229 : 223-225

Acanthagrion speculum Garrison, 1985

Figs. 1b , 2a, c , 3 a–b, d, 4b, d, 5c–d, 6c, 8

Specimens examined: Six exuviae (1♂, 5♀♀), eight F-0 larvae (4♂♂, 4♀♀). COSTA RICA: Turrialba, CATIE (9.8906°, –83.6545°), elevation 611m, 1 F-0 larva (♀ reared), 09 May 2018, J. Román-Heracleo leg., emerged on 16 May 2018; same data but 3 ♀♀ emerging, 22 August 2018; same data but 2 F-0 larvae 24 Sep 2018 (1♂ reared, emerged on 25 Sep 2018, 1♀ reared emerged on 29 Sep 2018); same data but 5 F-0 larvae (3♂♂, 2♀♀), 21 No- vember 2018; same data but 3 F-0 larvae (1♂, 2♀♀), 19 January 2019. Sarapiquí, Reserva Biológica Tirimbina, lake (10.4238°, –84.1051°) elevation 163m, 2 F-0 larvae (♂♂), 27 October 2018, (1♂ emerged 29 October 2018, 1♂ died), P. E. Gutiérrez-Fonseca, J. Román-Heracleo, leg. Specimens deposited at IEXA (4 larvae), all other in MZUCR.

Description. Exuviae yellowish, mature larvae mostly yellowish-brown, slender, femora with preapical bands, caudal lamellae 80% of total body length ( Fig. 1b ). Larvae similar to A. trilobatum described above, except as follows:

Head. Antennomeres ( Figs. 2a, c ) 2–6 brown with apex yellow pale, 7th antennomere yellow pale, size proportions of antennomeres: 0.50, 0.70, 1.0, 0.70, 0.50, 0.40, 0.10 ( Fig. 2c ). Prementum with 3 long setae, occasionally 2+1 ( Fig. 3d ), laterodorsally with a row of 6–9 spiniform setae. Labial palp with 3–4 long setae, usually 4 ( Fig. 3d ).

Thorax. Anterior and posterior wing sheaths reaching posterior margin of S4 and basal third of S5, respectively ( Fig. 1b ). Metathoracic legs long, when fully extended tips of tarsi reaching posterior margin of S8.

Abdomen. S1–9 with a thin pale middorsal line, S2–8 with a prominent lateral carina, S6–9 with lateral spines at posterior third of each segment, increasing in number (2–4 or 5 spines) and robustness caudad ( Fig. 1b ). Male gonapophyses, in ventral view ( Fig. 4b ) straight, sharply pointed, reaching basal 0.56 of sternum 10. Ventral view of female gonapophyses as in Fig. 4d . Caudal lamellae (Figs. 5c,d) eight times longer than widest part, measuring 44.6–45.5% of total body length; nodus inconspicuous, delimited by the lateral carina and the row of spines on the ventral margin of lateral lamellae; basal 0.7 of dorsal margin of lateral lamellae with two spines, basal 0.52 of ventral margin with 34 spines (Fig. 5d); basal 0.10 of dorsal margin of median lamella with two spines, basal 0.05 of ventral margin with two spines (Fig. 5c); remainder of margins in both median and lateral lamellae with a row of minute and very fine setae. Male cerci more or less as wide as long, conical, blunt-tipped (Fig. 6c).

Measurements (mm): Larvae only: TL 17.7–18; AL 7.6–8.2; PfL 1.9–2.0; MsfL 2.3–2.5; MtfL 3; MWh 2.8; CeL: 0.2; MgL 0.5 (Figure 5b); FgL 1.0 (Figure 5d). Lateral lamella length 7.9–8.2, maximum width 1.0. The largest measurements correspond to males.

Remarks. The CATIE is located on the Caribbean slope, in Turrialba, Costa Rica. Its lake ( Fig. 8a ) is man-made with influence of the surrounding agroforestry land. The aquatic vegetation is represented mostly by Nymphaea spp. and Eichhornia sp., and grasses of the Poaceae family on the shore. Larvae were collected from February 2018 to January 2019, associated with the roots below the leaves of the aquatic plants (water lily mainly), although the larvae found at the Tirimbina Lake ( Fig. 8b ) were found on muddy substrate. Adults emerged throughout the year, however, the highest emergence activity was during May (females) and September (males). Metamorphosis occurred 3─ 15 cm above the water surface, on vegetation.

Diagnosis. Acanthagrion trilobatum differed from A. speculum (characteristics of the latter in parentheses) by having 2–3 premental setae, rarely 3 (2 large +1 smaller or 3, usually 3); antennomere length proportions, especially 4 th antennomere 0.85 times the length of the 3 rd antennomere (0.70); labial palp with 4 long setae (3─4, usually 4); S2–8 with lateral carina and spiniform setae (S2–8 with lateral carina, but only S6– 9 with spiniform setae); male gonapophyses slightly incurved (straight); male cerci widely rounded at apex (bluntly-pointed); caudal lamella 41.1–44.7% of body length (44.6–45.5%); tracheal pattern appearing with incipient, dark, transversal bands, secondary trachea diffuse (tracheal pattern lighter, no faint of any transversal band especially in lateral lamellae, secondary trachea well-marked).

Figures

FIGURE 1. Dorsal habitus of the larvae of: a) A. trilobatum; b) A. speculum.

FIGURE 2. Morphological details of the larvae. Figs. a and c, A. speculum; b and d, A. trilobatum. a) Head, dorsal view; b) Right antenna, dorsal view; c) Left antenna, dorsal view; d) Distal apex of metatibiae showing tridentate setae.

FIGURE 3. Morphological details of the larvae. Figs. a, b and d, A. speculum; c, e and f, A. trilobatum. a) Mandibles, ventrointernal view; b) Right galeolacinia, ventral view; c) and d) Prementa, dorsal view; e) Right labial palp, anterior view; f) Prementum teratology, ventral view, showing bilobate ligula.

FIGURE 4. Morphological details of the abdominal segments 9–10 of the larvae. Figs. a and c, A. trilobatum; b and d, A. speculum. a–b, Male gonapophyses, ventral view, c–d, Female gonapophyses, ventral view.

FIGURES 7–8. FIGURE 7. Lake El Rodeo, San José, Costa Rica. Habitat of Acanthagrion trilobatum. FIGURE 8. Habitat of Acanthagrion speculum: a) Lake CATIE, Turrialba, Costa Rica; b) La Tirimbina, Sarapiquí, Costa Rica.