Mecidea major, Sailer, 1952

Mcpherson, J. E. & Bundy, C. Scott, 2021, Identification of Nymphal Instars of Mecidea major Sailer and Mecidea minor Ruckes (Hemiptera: Heteroptera: Pentatomidae: Mecideini) fromtheSouthwestern and Central United States, Zootaxa 4958 (1), pp. 479-488 : 480-487

Key to Nymphal Instars of Mecidea major and M. minor 1

1 Tylus longer than juga; nota without distinct dorsal submedial and sublateral longitudinal stripes; posterior margin of mesonotum almost straight, weakly to not extended posteriorly ( Figs. 5 and 12 ); thoracic pleura brown, without stripes ( Figs. 19 and 24 ); length less than 1.20........................................................................... first instar2

- Tylus longer to shorter than juga; nota with distinct submedial and sublateral longitudinal stripes; posterior margin of mesonotum moderately to strongly extended posteriorly (e.g., Figs. 6–7 , 13–14 ); thoracic pleura usually with one to two longitudinal stripes, one dorsal, one ventral ( Figs. 20–23 , 25–28 ); length more than 1.70....................................... 2

2 Medial abdominal plates 1–3 with anterior margin heavily bordered with dark brown except medially ( Figs. 6–11 ); thoracic pleura usually with one longitudinal stripe (dorsal) ( Figs. 20–23 ); body in older instars (3rds–5ths) broadly elongate-oval ( Figs. 7– 11 ) ( M. major )..................................................................................... 3

- Medial abdominal plates 1–3 with anterior margin narrowly dark brown except white medially or completely white, heavy brown area confined to lateral/sublateral areas ( Figs. 13–18 ); thoracic pleura generally with two longitudinal stripes, one dorsal, one ventral, but ventral stripe may be absent ( Figs. 25–28 ); body in older instars (3rds–5ths) narrowly elongate-oval ( Figs. 14–18 ) ( M. minor ).................................................................................... 6

3 Tylus longer than juga ( Fig. 6 ); antennal segment 2 with dorsal surface rounded; mesonotum with posterior margin weakly extended posteriorly, straight laterally ( Fig. 6 ); thoracic pleura usually with longitudinal stripe well developed and unbroken ( Fig. 20 ); lengths, 2.06 ± 0.03 (2.02 ± 0.03); widths, 0.92 ± 0.02 (1.09 ± 0.02)............................second instar

- Tylus subequal to shorter than juga ( Figs. 7–11 ); antennal segment 2 with dorsal surface carinate; mesonotum with posterior margin strongly extended medially, arcuate laterally ( Figs. 7–11 ); thoracic pleura usually with longitudinal stripe usually well developed, but may be broken in lighter forms ( Figs. 21–23 )................................................... 4

4. Tylus and juga subequal in length, wing pads lacking ( Fig. 7 ); lengths, 3.17 ± 0.07 (3.16 ± 0.06); widths, 1.31 ± 0.01 (1.75 ± 0.04)....................................................................................... third instar

- Tylus shorter than juga, leaving apical notch, wing pads easily discernible ( Figs. 8–11 ).............................. 5

5 Wing pads shorter, reaching abdominal segment 2 ( Figs. 8–9 ); lengths, 4.51 ± 0.15 (4.53 ± 0.15); widths, 2.00 ± 0.04 (2.40 ± 0.09)...................................................................................... fourth instar

- Wing pads longer, reaching abdominal segment 3 or 4 ( Figs. 10–11 ); lengths, 7.62 ± 0.17 (7.78 ± 0.17); widths, 2.92 ± 0.06 (2.99 ± 0.11).................................................................................. fifth instar

6 Tylus and juga subequal in length ( Fig. 13 ); antennal segment 2 with dorsal surface rounded; mesonotum with posterior margin weakly extended medially, nearly straight laterally ( Fig. 13 ); thoracic pleura usually with two well-developed stripes, which are unbroken ( Fig. 25 ); lengths, 1.82 ± 00.8 (1.81 ± 0.08); widths, 0.79 ± 0.02 (0.94 ± 0.03)....................second instar

- Tylus shorter than juga, leaving apical notch shorter than juga ( Figs. 14–18 ); antennal segment 2 with dorsal surface carinate; mesonotum with posterior margin moderately to strongly extended medially, arcuate laterally ( Figs. 14–18 ); thoracic pleura usually with two well-developed stripes, which may be broken in lighter forms ( Figs. 26–28 )......................... 7

7 Wing pads lacking ( Fig. 14 ); lengths, 3.05 ± 0.05 (3.08 ± 0.05); widths, 1.05 ± 0.02 (1.23 ± 0.04).............. third instar

- Wing pads easily discernible ( Figs. 15–18 )................................................................. 8

8 Wing pads shorter, reaching abdominal segment 2 ( Figs. 15–16 ); lengths, 4.52 ± 0.12 (4.63 ± 0.12); widths, 1.54 ± 0.02 (1.70 ±0.04)..................................................................................... fourth instar

- Wing pads longer, reaching abdominal segment 3 or 4 ( Figs. 17–18 ); lengths, 6.64 ± 0.16 (6.89 ± 0.16); widths, 2.35 ± 0.02 (2.20 ± 0.05).................................................................................. fifth instar

1 Length was measured from apices of tylus and juga to apex of abdomen (two measurements); width across mesonotum and abdominal segments 3–4, whichever was widest (both measurements shown).

2 First instars of M. major and M. minor cannot be distinguished easily using morphological characters.

Figures

FIGURES 5–7. Mecidea major nymphs (dorsal view). 5. First instar. 6. Second instar. 7. Third instar. Scale bars = 0.5 mm. (From Bundy & McPherson 2018).

FIGURES 12–14. Mecidea minor nymphs (dorsal view). 12. First instar. 13. Second instar. 14. Third instar. Scale bars = 0.5 mm. (From Bundy & McPherson 2011).

FIGURES 19–23. Mecidea major nymphs (ventrolateral view). 19. First instar. 20. Second instar. 21. Third instar. 22. Fourth instar. 23. Fifth instar.Arrow indicates position of pleural longitudinal stripe. Scale bars = 1.0 mm.

FIGURES 24–28. Mecidea major nymphs (ventrolateral view). 24. First instar. 25. Second instar. 26. Third instar. 27. Fourth instar. 28. Fifth instar.Arrows indicate positions of pleural longitudinal stripes. Scale bars = 1.0 mm.

FIGURES 8–11. Mecidea major nymphs (dorsal view). 8. Fourth instar, light form. 9. Fourth instar, dark form. 10. Fifth instar, light form. 11. Fifth instar, dark form. Scale bars = 0.5 mm. (From Bundy & McPherson 2018).

FIGURES 15–18. Mecidea minor nymphs (dorsal view). 15. Fourth instar, light form. 16. Fourth instar, dark form. 17. Fifth instar, light form. 18. Fifth instar, dark form. Scale bars = 0.5 mm. (From Bundy & McPherson 2011).