Research Article |
Corresponding author: Daniel Edwin Domínguez-León ( biologiaunamedwin@gmail.com ) Academic editor: Vinicius S. Ferreira
© 2022 Martín L. Zurita-García, Daniel Edwin Domínguez-León, Viridiana Vega-Badillo, Mireya González-Ramírez, Ishwari Giovanni Gutiérrez-Carranza, Geovanni M. Rodríguez-Mirón, Sara López-Pérez, Paulina Cifuentes-Ruiz, Miriam Aquino-Romero, Santiago Zaragoza-Caballero.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Zurita-García ML, Domínguez-León DE, Vega-Badillo V, González-Ramírez M, Gutiérrez-Carranza IG, Rodríguez-Mirón GM, López-Pérez S, Cifuentes-Ruiz P, Aquino-Romero M, Zaragoza-Caballero S (2022) Life cycle and description of the immature stages of a terrestrial firefly endemic to Mexico: Photinus extensus Gorham (Coleoptera, Lampyridae). ZooKeys 1104: 29-54. https://doi.org/10.3897/zookeys.1104.80624
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The life cycle, morphology, and bionomy of Photinus extensus Gorham, 1881, an endemic species of Mexico, are described. Redescriptions of adults (male and female) are also presented. Larvae were reared to the adult stage from eggs laid by females collected at the El Pedregal de San Ángel Ecological Reserve, south of Mexico City. The activity period of adults of P. extensus begins at the end of July and finishes by the end of August. Females lay between 3 and 198 eggs. Larvae hatch from the eggs after a period of 11 to 71 days, undergo 6 larval instars and a pupal stage in an annual cycle. Morphological characters of the sixth larval instar of P. extensus are compared with those of several other genera assigned to the tribe Photinini. Knowledge of the natural history of firefly larvae is relevant since most species do not feed as adults and therefore depend on resources acquired during the larval stage.
Bionomics, egg, larva, Photinini, pupa, redescription
Fireflies belong to the family Lampyridae Rafinesque, 1815, and show a wide-ranging phenotypic and ecological diversity (
Firefly species can be either diurnally or nocturnally active. Diurnal species generally do not have light organs as adults and rely on pheromonal and visual cues (
Firefly larvae can be aquatic, semiaquatic or terrestrial and can be found along the margins of streams and ponds as well as in leaf litter or rotten logs (
Currently, only the morphology of a small percentage of lampyrid larvae, at the generic or specific levels, of the approximately 144 genera and 2400 species, is known (
Photinus Laporte, 1833 is the most diverse genus of the subfamily Lampyrinae with more than 300 described species (
In the past 20 years the number of known Photinus species has increased due to the description of new species from Mexico (
As for most genera in the family Lampyridae, Photinus larvae are poorly studied.
This paper documents the life cycle and larval morphology of a Photinus species for the first time. Photinus extensus Gorham, 1881 is an endemic species of Mexico. Its known distribution includes the state of Chiapas, Hidalgo, Mexico, Morelos and Mexico City (
Adults of P. extensus were collected in the buffer zone of the El Pedregal de San Ángel Ecological Reserve (19°19'28.82"N, 99°11'20.95"W); this zone is between the core zone and the urban area of Mexico City, it is totally in the territory of the Universidad Nacional Autónoma de México. El Pedregal de San Ángel Ecological Reserve is located at the Southeast of Mexico City in the central Campus of the (
To observe the reproductive activity of P. extensus, adult specimens collected were divided into 14 groups consisting of five males and one female were placed in an 8 × 15 cm plastic container; peat moss substrate was added to simulate their natural environment. After oviposition, eggs were placed over a gauze patch in a 50 × 100 mm Petri dish, and moistened every 48 hours with an antimycotic solution based on Nistatine diluted in water (1/10). After eclosion, larvae werepartitioned into groups of five in separate Petri dishes (5×10 mm). To avoid dehydration, a filter paper layer was added and moistened every two days. This filter paper was replaced every week. Starting with the fourth larval instar, each larva was placed in a separate Petri dish (5×10 mm), with half of the dish covered with the filter paper, and the other half filled with sterilized dry sawdust. Following previous studies (
Adults were identified using original descriptions, literature (Zaragoza-Caballero et al. 2000), and by comparison with photographs of type specimens (Natural History Museum of London, BMNH) (Fig.
Morphological larval characters of known Photinini genera (after
Character | Pyractonema nigripennis Solier | Pyropyga nigricans (Say) | Lucidota atra Olivier | Lucidina accensa Gorham | Phosphaenus hemipterus (Goeze) | Photinus extensus Gorham |
---|---|---|---|---|---|---|
Body shape | Narrow, parallel 5.7–6.1× longer than narrow | Narrow, parallel | Narrow, parallel | Wide, suboval 4.2× longer than narrow | Oblong and narrow ~4.5× longer than narrow | Narrow, parallel ~5× longer than narrow |
Ratio: body length/thoracic length | 2.8–3.1 | 3.4–3.7 | 3.4–3.7 | 2.6 | 3.14 | 2.9 |
Cephalic capsule | Short and wide, retractable into the thorax | Short and wide, retractable into the thorax | Short and wide, retractable into the thorax | Subquadrate, moderately flattened dorso-ventrally. | Rectangular, retractable into the thorax | Short and wide, retractable into the thorax |
Antennae | Wide, partially retracted into the head | Wide, partially retracted into the head | Wide, partially retracted into the head | Long and thin, completely retracted into the head | Long and thin, partially retracted into the head | Long and thin, partially retracted into the head |
Opening of the mandible channel | At the exterior margin, subapical | At the exterior margin, subapical | At the exterior margin, subapical | At the exterior margin, subapical | At the exterior margin, subapical | At the exterior margin, subapical |
Number of retinacula of the mandible | 1 | 1 | 2 | 4 | 1 | 1 |
Maxillar palp | Three palpomere | Three palpomere | Three palpomere | Two palpomere | Tew palpomere | Four palpomere |
Shape of pronotum | subcircular | subcircular | subcircular | subcircular | subcircular | suboval |
Shape of mesonotum | sub oval | sub oval | sub oval | trapezoidal | sub oval | rectangular |
Shape of metanotum | sub oval | sub oval | sub oval | rectangular | sub oval | rectangular |
Thorax color | Dark with three pale, longitudinal, and subparallel lines | Dark with three pale, longitudinal and subparallel lines | Dark with three pale, longitudinal and subparallel lines | Almost blackish brown, lateral and hind margins more or less paler than the ground Subrectangular | dorssally dark reddish-brown, ventrally pink/ochre/light brown with darker plates on laterotergites and sternum | Dark, with pale stripes |
Shape of the abdominal tergites | Subrectangular, except VII–IX subsquared | Suboval | Suboval, posterior margin of tergites V–VIII straight | Subrectangular | I–VII, IX subrectangular, VIII suboval | Subrectangular |
Abdomen color | With a clear line on each side. Dark segments VII–IX. | Dark with pale lateral areas (segments I–VIII) | Dark with three pale longitudinal and subparallel lines, at the inner interior margin | Almost blackish brown, lateral and hind margins more or lesspaler than the ground I–VI, segments VII–X pale yellowish to milky white | pink/ochre/light brown | Pale with a little pink stripe in the second third in segments I–V, the rest of them pale |
Images were taken with an AxiocamMRC5 camera attached to a Zeiss Axio Zoom V16 microscope with an objective lens Plan NeoFluar Z, 1×10.25 FWD 56 at the Laboratorio de Microscopía y Fotografía de la Biodiversidad II, Instituto de Biología,
(Fig.
Head. Interocular space flat, almost parallel, shagreen-like integument, brilliant and pilose; frons vertical, interantennal distance (0.17–0.22 mm; 0.2 ± 0.01 mm) slightly wider than the antennal fossae (0.23–0.32 mm; 0.28 ± 0.04 mm); eyes finely faceted, semispherical, prominent, longer (1.1–1.18 mm; 1.17 ± 0.03 mm) than wide (0.62–0.98 mm; 0.9 ± 0.08 mm); antennae filiform, long (5.7–7.11 mm; 7.0 ± 0.11 mm), one-and-a half times longer than pronotum, extending beyond the posterior coxae, scape claviform reaching a length of (0.69–0.98 mm; 0.79 ± 0.10 mm), as long as the next two antennomeres together, the second short (0.19–0.79 mm; 0.28 ± 0.05 mm), the third to the tenth (0.54–0.71 mm; 0.66 ± 0.07 mm), the eleventh reaches (0.51–0.73 mm; 0.77 ± 0.03 mm); frontoclypeal suture membranous, almost straight; clypeus trapezoidal, anterior margin concave, with setae along the margin; mandibles falcate, robust, with setae on the external base; maxillar palpomere ogival and robust, labial palpomere securiform.
Thorax. Pronotum wider (3.95–4.4 mm; 4.04 ± 0.08 mm) than long (2.8–3.4 mm; 3.01 ± 0.27 mm), semicircular, with a longitudinal groove indistinct in the basal half, anterior margin rounded, posterior sinuate, posterior angles straight, sides narrowly explanate, with irregular glandular pores at the front and ordered on the posterior and lateral margins, surface brilliant, abundant pilosity, decumbent; scutellum spatulate, with the posterior margin rounded, surface brilliant, punctate and decumbent pilosity; long elytra, parallel, four and a half times longer (12–13.5 mm; 12.6 ± 0.57 mm) than wide (2.4–2.8 mm; 2.58 ± 0.19 mm), surface rugose, opaque, with two types of pilosity, one relatively long and erect, the other small and procumbent; mesothoracic respiratory spiracles not tubular; long legs, pro, meso and metalegs similar to each other, femurs fusiform, tibiae channeled, a little dilated at the apex, external margin crenulate, two symmetric tibial spurs present in pro, meso and meta legs, tarsomeres laterally compressed, first metatarsomere longer (0.6–0.76 mm; 0.73 ± 0.03 mm) than the next two metatarsomeres together (0.51–0.68 mm; 0.63 ± 0.08 mm), fourth bifid, covering the fifth, claws simple.
Abdomen. Sternites 5–6 longer than the preceding, with stigmatiform pores, posterior margin of sternite six cleaved, the seventh concave, the eighth ojival; posterior margin of pygidium convex; aedeagus short, robust, with symmetrical basal piece (0.67–0.7 mm; 0.68 ± 0.05 mm), as long as lateral lobes (0.66–0.7 mm; 0.67 ± 0.45 mm), with posterior margin concave, lateral lobes apically acute and convergent, median lobe cylindrical, with dorsal part membranous and ventral part with sclerosed base and apical half membranous, dorso-basal excrescences as long, oblique lobes, median orifice apical, lateral lobes narrowing towards the apex, apex blunt and wide (Fig.
(Fig.
Head. Interocular space flat, more or less parallel, shagreen integument, brilliant and pilose, frons vertical, interantennal distance (0.16–0.37 mm; 0.25 ± 0.10 mm) wider than antennal fossae (0.16–0.37 mm; 0.44 ± 0.16 mm) ; eyes small, finely faceted, semispherical, longer (0.65–0.94 mm; 0.67 ± 0.25 mm) than wide (0.45–0.76 mm; 0.54 ± 0.15 mm), antennae filiform, short (4.16–5.52 mm; 5.23 ± 0.96 mm), as long as the length of pronotum, without extending beyond the posterior margin of metasternum; scape reaching a length of (0.57–0.64 mm; 0.58 ± 0.34 mm), longer than the two next antennomeres together, the second short (0.2–0.39 mm; 0.37 ± 0.06 mm), from the third to the tenth (0.35–0.58 mm; 0.44 ± 0.07 mm), the eleventh reaches (0.54–0.69 mm; 0.68 ± 0.05 mm); frontoclypeal suture membranous, almost straight; clypeus trapezoidal, anterior margin concave, with setae along the margin; mandibles falcate, robust with setae on the external base; maxillar palpomere ogival and robust, labial palpomere securiform.
Thorax. Pronotum wider (3.27–4.97 mm; 4.21 ± 0.86 mm) than long (2.21–2.6 mm; 2.2 ± 0.2 mm), semicircular, with a longitudinal groove indistinct on the basal half, anterior margin rounded, posterior margin straight, posterior angles straight, sides narrowly explanate, with glandular pores irregular at the front and ordered on the posterior and lateral margins, surface brilliant, pilosity abundant, decumbent, scutellum spatulate, with the posterior margin rounded, surface brilliant, punctate and pilosity decumbent; elytra short, without covering the abdomen, two-and-a-half times longer (4.62–6.5 mm; 5.2 ± 0.62 mm) than wide (1.91–2.71 mm; 2.22 ± 0.42 mm), surface rugose, opaque, pilosity decumbent; divergent in the median margin, epipleura reduced, mesothoracic respiratory spiracles not tubular; legs similar to each other; tibiae and femurs flat, fusiform, tibiae channeled, a little dilated at the apex, external margin crenulate, tarsomeres laterally compressed, first metatarsomere (0.41–0.64 mm; 0.62 ± 0.22 mm) slightly longer than the next two together (0.46–0.58 mm; 0.53 ± 0.06 mm), the fourth bifid, covering part of the fifth, claws simple.
Abdomen. Sternites 5–6 longer than the preceding, without stigmatiform pores, posterior margin of sternite six almost straight, the seventh cleaved, the eighth with a notched; posterior margin of pygidium convex. Internal genitalia with a short and rounded spermatophore-digesting gland, longer than spermatheca, bursa copulatrix with an elongated and weakly sclerotized plate. Ovipositor with valvifers free, two-and-a-half times longer (2.41–3.10 mm; 2.75 ± 0.48 mm) than coxites (1–1.12 mm; 1.06 ± 0.08 mm); coxites divergent posteriorly; styli minute, sclerotized; proctigerplate short with rounded posterior margin, well-sclerotized (Fig.
Description of pre-imaginal stages.
Semispherical shape, whitish, with a diameter of approximately 290–300 µm (Fig.
Description. Elongate, tapering body, dorso-ventrally flattened, length 12.27–18.18 mm; integument of granular appearance; tergites from protergum to abdominal segment IX divided by sagittal line in dorsal view. Tergites with two lateral pale stripes that run throughout the body to the VIII segment, more sclerotized than the sternites, with clearly visible setae on the posterior margin of tergites VII to X; the last tergum completely dark except the lateral margins paler; anterior margin of the first head segment with two fossae (sensorial or glandular) paler and bigger than the rest of the punctations of the segment. Membranous pleura except for a dark sclerotized area around the spiracles, without apparent setae. The ventral surface is flexible due to the intersegmental membranes. Mesothoracic and abdominal pleural areas of segments I–VIII with bilabiate spiracles.
Head capsule. Prognathous; slightly visible when retracted into prothorax due to the transparency of the protergum; extensible neck membrane covered in extremely short spines forms a two-layer envelope around the head; partially retractable within the prothorax; completely sclerotized, small, wider (0.88–1.54 mm; 1.2± 0.27 mm) than long (0.68–1.09 mm; 0.92 ± 0.17 mm), flat, sides almost parallel; stemmata on each side, with an almost transparent spot located posteriorly to the stemmata; clypeus and labrum fused forming the clypeo-labrum covering base of the mandibles in dorsal view; maxillae and labium connate forming maxillolabial complex covering most of the ventral cephalic area; epicranial suture dark, U-shaped, with a very short epicranial stem, frontal arms V-shaped (Figs
Sixth instar of Photinus extensus Gorham A SEM image of the head retracted and anterior part of prothorax in lateroanterior view B antennae C prementum, maxillary palpus and galea (lateroventral) D distal part of galea E, F maxillary palpi in ventrolateral view G right metathoracic leg in ventrolateral view H pretarsus.
Antenna. Trimerous, located on the distal margin of the epicranial plate; partially retractable into the antennal socket; three-segmented, basal antennomere and second antennomere (0.42–0.55 mm; 0.48 ± 0.05 mm) elongated, and a third segment (the flagellum) short (0.24–0.31 mm; 0.26 ± 0.03 mm); adjacent sensorial cone present; basal antennomere with two long setae in the anterior mid, almost entirely covered by moderately dense, second antennomere with long setae close to apex and entirely covered by dense smaller finer setae, third antennomere with long setae from base to apex, with short setae on the anterior margin (Fig.
Maxilla. Consisting of five parts, attached to lateral margins labium forming a maxillo-labial complex. Cardo elongate, irregular shape, with four setae in ventral surface, on long setae in posterior margin. Stipes elongated, ventrally covered with erect setae, with three long stout setae placed radially on the ventral apical region. Galea present, with two segments, the first longer and stouter than the apical, which is triangular (Fig.
Labium. Closely attached to maxilla, formed by prementum, mentum and postmentum. Prementum heart-shaped, surface covered with numerous short setae and two long setae close apex; labial palpi with two segments, basal palp subquadrate with few setae in mid-region, distal palp conical without setae; mentum with one pair of setae on anterior third and one pair of setae on posterior third; postmentum elongate, slightly sclerotized at the medial base, laterally united by membranes to the cardines; with a setae on each side near the base.
Mandible. Symmetrical, falcate, strongly sclerotized, with an internal channel opening subapically on outer edge. Penicillus well-developed. Retinaculum short and rounded, present only as a blunt protuberance on basal third of the mandible. Densely covered by fine setae on the external margins basely, basal half on inner margin of mandible covered with a brush of stout setae, being longest on the retinaculous protuberance (8E, F); mesal margin serrate.
Thorax. Protergum wider (2.43–3.81 mm; 3.14 ± 0.57 mm) than long (1.54–2.59 mm; 2.11 ± 0.43 mm), subsemicircular, wider posteriorly, rounded at posterolateral corners, covering the retracted head. Meso- and metatergum subrectangular three times wider than long, delimited by a pleural suture elongate barely evident from the laterotergites. Lateral areas of meso and metathorax scarcely sclerotized, composed of two laterotergites, the anterior with a well-developed spiracle on the mesothorax. Episterna extending from the anterior part to the lateral part of the coxae; epimeron forming a little sclerotized stripe, parallel to the coxae.
Legs. Pentamerous, the first pair of forelegs slightly shorter than the second and third. Coxae short (0.76–1.16 mm; 0.98 ± 0.18 mm), cylindric, widely separated at the base, decumbent; coxal-trochanteric membrane reaching about 1/3 of the coxal length. Trochanters pentagonal, joining the femur obliquely (0.51–0.82 mm; 0.71 ± 0.13 mm). Femur narrow and cylindrical in lateral view. Tibiotarsus narrowing distally with stout setae. All legs with a double row of long setae in the inner margin, numerous short setae in the outer margin: pretarsus claw-like with two setae at base (Figs
Abdomen. Tergites III–IX of similar length (0.86–1.36 mm; 1.09 ± 0.17 mm), width almost constant; segments I–VIII (or I–VII) wider than long, bearing a pair of long stout setae posterolaterally, with laterotergites at each side, with sclerotized plates containing the spiracles; ventral area of segments I–VIII with sternal areas almost squared, slightly pigmented, sternites with two long setae in mid-region; sternal medial area margined by laterosternites – sometimes pigmented, elongate, narrow, and paired, delimited by laterotergites dorsally, and ventrally by a medial sternal plate; ventral area of segment IX with a simple plate, without area differentiation; light organ present and segment VIII indistinct; abdomen ending with a series of eversible filaments (pygopodia) bifurcate at the apex, at least 30 pygopodia arise from 12 basal stalks which may branch more than once (the dorso and ventrolateral stalks branch into three); densely packed recurved hooks occur on the ventrolateral surface of each exerted pygopod and completely covering at apex, with toothed scales on the dorsolateral surface only on anterior half. (Fig.
Description. Similar to sixth instar. Length 11.45–13.78 mm. Head capsule. Wider (0.82–0.96 mm; 0.92± 0.05 mm) than long (0.57–0.85 mm; 0.71 ± 0.12 mm). Antenna. Basal antennomere and second antennomere (0.28–0.35 mm; 0.32 ± 0.02 mm), and a third segment (the flagellum) (0.15–0.21 mm; 0.18 ± 0.02 mm). Maxilla. Maxillae with three-segmented palpi, basal segment long (0.34–0.54 mm; 0.43 ± 0.07 mm) covered by setae in mid region, segment II wider (0.30–0.43 mm; 0.36 ± 0.06 mm) than long (0.12–0.17 mm; 0.14 ± 0.02 mm); apical segment cylindrical (0.10–0.13 mm; 0.11 ± 0.01 mm). Thorax. Protergum wider (1.36–1.53 mm; 1.4 ± 0.06 mm) than long (1.18–1.68 mm; 1.3 ± 0.20 mm), trapezoidal. Legs. Coxae short (0.77–0.97 mm; 0.86 ± 0.08 mm), femur obliquely (0.43–0.60 mm; 0.52 ± 0.07 mm). Abdomen. Tergites III–IX (0.68–0.85 mm; 0.77 ± 0.045 mm) ventral area of segments I–VIII with sternal areas almost squared, slightly pigmented, sternites with two long setae in mid-region.
Description. Similar to sixth instar. Length 3.72–8.80 mm; after hatching, the first instar body does not appear sclerotized to the degree found in later instars. Head capsule. Wider (0.48–0.72 mm; 0.6± 0.10 mm) than long (0.24–0.51 mm; 0.38 ± 0.12 mm), s (Figs
Thorax. Protergum wider (0.73–1.47 mm; 0.94 ± 0.21 mm) than long (0.51–0.75 mm; 0.53 ± 0.09 mm). Legs. Coxae short (0.44–0.65 mm; 0.53 ± 0.08 mm), femur obliquely (0.21–0.34 mm; 0.27 ± 0.05 mm). Abdomen. Tergites III–IX (0.31–1.2 mm; 0.74 ± 0.28 mm).
Length 17–23 mm; width 6–7 mm. Body elongate, curved, ventrally concave, pale yellowish (sternites I–VIII slightly pigmented at the ends).
Head. Totally covered by the pronotum in dorsal view. Large eyes, located at the sides of the head; antennae in front of the eyes, nearer the frontal center, mouthparts visible in ventral view.
Thorax. Pronotum wider than long, semicircular, totally covering the head. Meso and metanotum shorter, subrectangular, bearing the elytra sidewards. All pairs of legs free, visible in ventral view. Spiracles present in the pleural areas of mesothorax.
Abdomen. Abdominal segments subrectangular, wider than long, spiracles present on abdominal pleural areas of segments I–VIII. Light organ on sternites V–VI.
In their natural habitat, adults of P. extensus are active from early July, when the first males can be observed. Bioluminescent activity begins at dusk, at approximately 20:00 h, and diminishes considerably an hour later. Male flight does not exceed 2 m in height. Females are brachypterous and perch in the undergrowth approximately 50 cm from the ground. Males flash every 4.5 seconds, flying in an arc when illuminated. When males detect a female, they wait for an intense flash as a response, which is brief. The flash intervals are of 10 to 20 seconds. Males react by flying lower and towards the female. Groups of 3 to 5 males commonly compete with each other to get the female first, to mate with her. Two types of competition were observed among males: 1) a mating ball: four or more males cover the copulating pair and try to dislodge the copulating male to gain access to the female, and 2) males using their pronotum as a lever to pry a copulating male from the female. In the laboratory, copulation was observed to last from between 2 to more than 4 hours.
During oviposition, females bend their abdomen and place the apical part of it on the substrate. Eggs are laid superficially or buried, randomly distributed, individually, or in groups (up to aggregates of 50). The number of eggs deposited by each female varied from three to 198. Eggs emit a faint bioluminescence since they are oviposited, which is only perceptible to the human eye in complete darkness. In total, 956 eggs from 13 females were obtained.
Under lab condition P. extensus completed its development in approximately 12 months, from oviposition to imago. The egg stage under laboratory conditions had a duration of 11 to 70 days, with mortality of n = 144 eggs (15%).
Photinus extensus undergoes six similar larval instars that differ in both size and color (Fig.
Photinus extensus has six instars; they are very similar and only differ in size, color and the degree of the body sclerotized and presence of setae. Instar III differs from I and VI by a trapezoidal pronotum (Fig.
Frequently, the identification and description of larvae in the tribe Photinini is based on the characters present in the final larval instar, mostly body shape, color pattern, head capsule features, and the morphology of mouthparts (
The distribution of the setae is different between genera (Table
Photinus extensus Gorham | Pyractonema nigripennis Solier | Lucidota atra Olivier | |
---|---|---|---|
Hypopharynx | Margin covered by dense pubescence. | Surface covered by dense pubescence. | No information. |
Mandible | With patches of dense pubescence in the basal part in ventral Margin covered by dense pubescence. With patches of dense pubescence in the basal part in ventral view. Mid-region covered by a single row of long setae. | With patches of dense pubescence in ventral view. Mid-region covered by only one row of setae. | Mid-region covered by only one row of long setae. One long seta close to the apex. |
Cardo | With 4 long setae in ventral surface and one long seta in the posterior margin. | With 13–15 setae in ventral surface. | Without setae. |
Maxillary palpomeres | Basal palp covered by setae in the mid region. Distal palp with setae from base to mid region. | Basal palp covered by setae. Palp II with some setae. Last palp without setae. | Basal palp with long setae from the mid region to the apex. Palp II with shorter setae. Distal palp without setae. |
Labial palpomeres | Basal palp with few setae in mid region. Distal palp without setae. | Basal palp with some setae. Distal palp without setae. | Basal palp with few long setae. Distal palp with one long seta. |
Prementum | Surface with many setae. Two long setae close to apex. | Dorsal and ventral surface with many setae. | With two basal regions of very fine setae, with longer setae on the palp segment. |
Submentum | With two long setae in mid region. | With two long setae in the basal middle. | No information. |
Antennomeres | Apex with two long setae. Antennomere III with long setae from base to apex. | All antennomeres covered by setae. Antennomere III with many short setae. | Basal antennomer with mid region covered by setae. Anterior region with longer setae. Antennomere II covered evenly by long setae. Antenomere III with short setae. |
Legs | With a double row of long setae in the inner margin. Outer margin with many setae. Pretarsus with two setae at the base. | With a double row of long setae in the inner margin. Pretarsus with two setae at the base. | With a double row of long setae in the inner margin. Pretarsus with two setae at the base. |
Abdomen | Sternites with two long setae in mid-region. | Sternites with two long setae in mid-region. | No information. |
The larval characters have shown to be important to clarify the phylogenetic relationships as
The life cycle, morphology, and behavior of the species of Photinus are similar. Photinus carolinus Green, 1956, P. ignitus Fall, 1927, P. marginellus LeConte, 1852, P. pyralis (Linnaeus, 1767), P. greeni Lloyd, 1969, and P. extensus are the known species that produce spermatophores due to the prolonged time of copulation (
The length of the pupal stage varies slightly in Photinus. The pupal stage of P. extensus and P. carolinus has a duration of six days (
The complete life cycle of Photinus extensus, including descriptions of egg, larvae, and pupa, was documented for the first time. Larvae were reared in laboratory conditions to the adult stage from eggs. The six instar of P. extensus are very similar; they differ only in size and in the sclerotized degree.
Among Photinini larvae there are not many differences, differing in the number of segments in the maxillary palp and in the number of retinacula of the mandible; the shape of the body and pronotum, and the opening of the mandible channel follow a similar pattern. Life cycle information is essential to carry out protection and conservation actions for insects that are very sensitive to environmental changes, like fireflies. For example, the species that do not produce light are easily overlooked and the information about their life cycle is deficient. This results in “Data Deficient” categorization in evaluations of extinction risk. Thus, more studies are needed in which the life history, habitat associations, and microhabitat are detailed (
We thank Susana Guzmán (IBUNAM) for help with the use of the Zeiss equipment, and Berenit Mendoza (IBUNAM) for the electron micrographs. We are grateful to Marc A. Branham and Sarah Sander Lower for their work correcting the English text in the manuscript and their valuable comments. We also thank Simone Policena Rosa, Luiz Silveira and Oliver Keller for helping to improve the manuscript. We thank the Natural History Museum of London, Michael Geiser and Keita Matsumoto for providing photographs of the lectotype. MLZG, DEDL, PCR and IGGC field work; IGGC and DEDL designed the breeding method; DEDL, IGGC, MGR and VVB laboratory work; SZC and IGGC identified the species; VVB, MGR, GMRM and MAR produced the photographs. SLP and DEDL constructed tables 1 and 2. All authors wrote the manuscript, revised it, and discussed the data.