Table 1.
Taxon sampling. The antennae of 3 males and 3 females of each species were examined, BL = bioluminescent, LO = light organ.
Fig 1.
Diagram of adult firefly antennae with 11 antennomeres.
Scape and pedicel represent the first two antennomeres, antennomeres III – XI are flagellomeres. (A) filimorm antennae; (B) serrate antennae.
Table 2.
Mean sensilla counts and antennal areas of male and female fireflies.
Table 3.
Mean sensilla densities and scaled antennal areas of male and female fireflies.
Fig 2.
(A) Relationship between body size (pronotum length) and antennal area: antennal area is positively correlated with body size (R = 0.467; Spearman’s rho = 0.668, p < 0.0001); (B) Comparison of antennal area by activity time: there is no difference in antennal size between diurnal and nocturnal species (x̄Diurnal = 1.50 ± 0.6 mm2, x̄Nocturnal = 1.28 ± 1.07 mm2, DFDen = 5.0, F = 0.077, p = 0.7943); (C) Comparison of antennal area by sex: males have significantly larger antennae than females (x̄Male = 1.49 ± 0.9 mm2, x̄Female = 1.26 ± 0.9 mm2; DFDen = 33.4, F = 11.58, p = 0.0017).
Table 4.
Distribution of sensilla morphotypes across species.
Fig 3.
(A) mechanosensilla chaetica type 1 (C1) on the antenna of a Py. nigricans female (also pictured are cuticular pores (CP) and chemosensilla basiconica type B3); (B) mechanosensilla chaetica type 2 (C2) of a Py. nigricans male; (C) mechanosensilla campaniform sensilla (SC) of a Luciolinae sp. female (also pictured are sensilla basiconica type B13).
Fig 4.
(A) sensilla basiconica types 1 and 2 (B1 and B2) on the antenna of a P. corruscus female; (B) sensilla basiconica type 3 (B3) of a P. corruscus male; (C) sensilla basiconica type 7 (B7) of a P. corruscus male; (D) sensilla basiconica type 10 (B10) of a L. punctata female; (E) sensilla basiconica types 10 and 11 (B10 and B11) of a L. punctata male; (F) sensilla basiconica type 12 (B12) and cuticular pores (CP) on a Luciolinae sp. female; (G) sensilla basiconica type 12 (B12) with an apical pore (arrow) of a Luciolinae sp. female; (H) basiconica sensilla types 7 and 13 (B7, B13) and cuticular pores (CP) of a Luciolinae sp. female; (I) sensilla trichodea (T1) of a Pha. christineae male.
Fig 5.
Sensilla pores and unique sensilla.
(A) B1 sensilla with a single pore (arrow) and the sensilla peg slightly compressed into the dome base, on the antenna of a P. corruscus female; (B) multipored (arrows) peg of B3 sensilla of a P. corruscus male; (C) multipored (arrows) cone of B10 sensilla of a L. punctata male; (D) sensilla coeloconica (X1) of a P. corruscus female; (E) cone sensilla, surrounded by (broken) B3 sensilla on the antenna of a P. corruscus female.
Fig 6.
Evolution of sensilla morphotypes.
Sensilla presence (filled square) and absence (empty square) for each chemosensilla type across study species are marked in the data matrix. The most parsimonious gains and losses for each morphotype are marked with a hatchmark on the corresponding branches of the species cladogram.
Fig 7.
Antennal area and sensilla abundance by sex and activity.
(A) Positive correlation between antennal area and total sensilla number (N = 42, R2 = 0.389, Spearman’s rho = 0.6677, p < 0.0001): larger antennae tend to have more sensilla; (B) Negative correlation between antennal area and total sensilla density (N-42, R2 = 0.542, Spearman’s rho = -0.7094, df = 1, p < 0.0001): larger antennae tend to have a lower sensilla density; (C) Comparison of mean sensilla number between diurnal and nocturnal species: diurnal species have significantly more sensilla than nocturnal species (x̄Diurnal = 4768 ± 1495, x̄Nocturnal = 2349 ± 1242; DFDen = 5, F = 8.33, p = 0.0343); (D) Comparison of mean sensilla number between females and males: males have significantly more sensilla than females (x̄Male = 3776 ± 1919, x̄Female = 2995 ± 1638; DFDen = 38, F = 8.7, p = 0.0054).
Fig 8.
Mechanosensilla and Chemosensilla counts by activity and sex.
(A) Mechanosensilla counts (both sexes) by activity time: there is no significant difference between diurnal and nocturnal species (x̄Diurnal = 3503 ± 993, x̄Nocturnal = 1753 ± 1009; DFDen = 5.0, F = 4.88, p = 0.078); (B) Mechanosensilla counts (both activity times) by sex: there is no significant difference in mechanosensilla number between males and females (x̄Male = 2586 ± 1248, x̄Female = 2420 ± 1418; DFDen = 33.0, F = 0.21, p = 0.279); (C). Chemosensilla counts (both sexes) by activity time: there is no significant difference between diurnal and nocturnal species (x̄Diurnal = 1261 ± 1114, x̄Nocturnal = 595 ± 282; DFDen = 5.0, F = 3.81, p = 0.108); (D) Chemosensilla counts (both activity times) by sex: males have significantly more chemosensilla than females (x̄Male = 1188 ± 1041, x̄Female = 573 ± 307; DFDen = 33.0, F = 15.66, p = 0.0004).
Fig 9.
Mechanosensilla and Chemosensilla densities.
(A) Mechanosensilla densities (both sexes) by activity time: there is no significant difference between diurnal and nocturnal species (x̄Diurnal = 2576/mm2 ± 827, x̄Nocturnal = 2068/mm2 ± 1079, DFDen = 5.0, F = 0.477, p = 0.52); (B) Mechanosensilla densities (both activity times) by sex: males have a significantly higher density of mechanosensilla than females (x̄Male = 2265 ± 1102 per mm2, x̄Female = 2306 ± 915 per mm2; DFDen = 33.0, F = 0.558, p = 0.460); (C) Chemosensilla densities (both sexes) by activity time: there is no significant difference between diurnal and nocturnal species (x̄Diurnal = 813 ± 486 per mm2, x̄Nocturnal = 881 ± 914 per mm2; DFDen = 5.0, F = 0.025, p = 0.880); (D) Chemosensilla densities (both activity times) by sex: males have a significantly higher density of chemosensilla on their antennae than females (x̄Male = 1147 ± 952 per mm2, x̄Female = 556 ± 273 per mm2; DFDen = 33.0, F = 11.05, p = 0.0022).