DESCRIPTION OF THE PREIMAGINAL STAGES OF PYRACTOMENA BOREALIS (RANDALL, 1838) (COLEOPTERA: LAMPYRIDAE) AND NOTES ON ITS BIOLOGY

10 Pages·1998·2.8 MB·

by  M Archangelsky

PROC. ENTOMOL. SOC. WASH.
100(3), 1998, pp. 421-430
DESCRIPTION OF THE PREIMAGINAL STAGES OF PYRACTOMENA
BOREALIS (RANDALL, 1838) (COLEOPTERA: LAMPYRIDAE)
AND NOTES ON ITS BIOLOGY
Miguel Archangelsky and Marc A. Branham
The Ohio State University, Museum of Biological Diversity, 1315 Kinnear Rd., Colum-
OH
bus, 43212-1192, U.S.A. (e-mail: [email protected]); Current address for (MA):
Urquiza 1132, 1638 Vicente Lopez, Buenos Aires, Argentina.
—
Abstract. The preimaginal stages of Pyractomena borealis (Randall 1838) are de-
scribed and illustrated. Information on the biology is also included. A detailed description
of the functional morphology of the holdfast organ of the larva is presented together with
a schematic illustration, step by step, of the eversion process. Instructions on rearing
techniques are also provided.
Key words: Lampyridae, firefly, Pyractomena borealis, larvae, pupae, biology, holdfast
organ, rearing
—
Resumen. Los estadios preimaginales de Pyractomena borealis (Randall 1838) son
descriptos e ilustrados. Se incluye informacion sobre la biologia de esta especie. Tambien
se presenta una descripcion detallada de la morfologia funcional del organo "holdfast"
de las larvas de esta especie, asi como una ilustracion esquematica, paso a paso, del
proceso de eversion. Tambien se proveen instrucciones de cria para esta especie.
It is surprising that the biology of fire- gel 1912, Haddon 1915. Bugnion 1929,
flies, a group ofbeetles that has received so Costa et al. 1988). It should also be men-
much attention from a behavioral point of tioned that the larvae of several genera are
view, are still poorly known. Another as- difficult to tell apart, especially those ofthe
pect of this family of beetles that has also tribe Photinini (LaBella and Lloyd 1991).
been largely neglected is the study of their There are two main obstacles preventing an
immature stages. There are few descriptions easy association of adults with immatures.
of larvae from the New World and, with a The first is the apparent difficulty in rearing
few exceptions, most of those descriptions lampyrids in the laboratory; the other is that
are very brief. females are usually difficult to collect.
Of the 18 Nearctic genera ofLampyridae Rearing lampyrids is not as difficult as it
(Poole and Gentili 1996), only eight have may appear, and several genera such as Pyr-
described immature stages. Four of those actomena Melsheimar, Photinus Laporte
genera are known from immatures de- and Photuris Dejean have been reared suc-
scribed in Europe (Lampyris Geoffroy and cessfully in the laboratory (Williams 1917,
Phausis LeConte) and Brazil (Aspisoma La- McLean et al. 1972, Buschman 1977). The
porte and Bicellonycha Motschulsky) (Vo- second obstacle, that of finding females.
422 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
can be overcome by collecting larvae in the and two days after copulation the female
field, and rearing them through to the adult laid a cluster of eggs. Newly emerged lar-
stage. One final problem is that some spe- vae were offered snails which they accept-
cies spend multiple years as larvae (Wil- ed, and throughout the rearing process they
liams 1917, Hess 1920, Buschman 1977) were maintained on the same diet. In order
and, in at least some cases, such as Pyroc- to keep the container clean, the empty
tomeiui lucifero Melsheimar, the life cycles shells were removed every other day. The
can be heterovoltine (Buschman 1977). culture was subdivided as larvae reached
Green (1957) revised the Nearctic spe- the third instar to avoid an overcrowded en-
cies of Pyractomena Melsheimar and also vironment (however, cannibalism was never
included larval and pupal descriptions of observed).
four of the 16 Nearctic species: P. ecostata Several larvae of each instar were fixed
(LeConte), P. angulata (Say), P. borealis in boiling water, and stored in 75% alcohol.
(Randall), and P. punctiventris (LeConte). All the last (fifth) instar larvae were fixed
His descriptions are brief and make refer- by the end of July. Pupae were fixed in the
ence to general body shape and coloration. same way, but right after fixation they were
No details of features such as the head cap- punctured in two or three places with a
sule or the mouthparts are included; fur- minuten pin, thus preventing the swelling
thermore, in the case of P. borealis. the de- of the pupae and allowing the maintenance
scription is based on three larval exuviae. of their natural shape.
Buschman (1977) studied the biology of To study the larval morphology, several
some selected fireflies, among them Pyr- specimens were cleared in lactic acid and
actomena lucifera and provides a detailed dissected in order to obtain different parts
description of the life cycle of this species of the body (head capsule, mouthparts,
under both laboratory and natural condi- holdfast organ, etc.). These were arranged
tions (Buschman 1977, 1984). on slides using Hoyer's as the mounting
medium. Drawings were done using a dis-
Materials and Methods
secting microscope (Wild M5) and a com-
Mature larvae of Pyractomena borealis pound microscope (Wild M20), both with a
MA
were collected by on March 23, 1994 camera lucida. The schematic illustration of
at Cedar Bog Natural Preserve (Ohio). the eversion process of the holdfast organ
They were kept in a small plastic container was done using MacDraw II, version 1.1.
with a wet paper towel, and brought to the
laboratory. A small terrarium was made Pyractomena borealis (Randall)
—
with a rectangular plastic container (12 X Description of fifth larval instar. Body
20 X 7 cm); part of the lid was cut out and elongate, fusiform, slightly flattened dor-
replaced with a fine mesh to allow gas ex- soventrally (Fig. 1). Cuticle shiny on scler-
change and to avoid an excessive build up otized areas, granulose with short clubbed
of humidity. Fine sand mixed with some setae on clear granules, areas with dark
soil (80% sand and 20% soil) was used as granules lacking setae (Fig. 8). Color pat-
the substrate and, on top, small pieces of tern variegated, ranging from light brown
bark were added. The substrate was kept to dark brown. Length: 17.0 to 22.0 mm.
moist during the entire rearing process. Length of remaining instars: first = 3.5 to
Small aquatic snails were offered to these 4.5 mm; second = 7.0 to 8.5 mm; third =
larvae, but those were refused and pupation 9.0 to 1 1.0 mm; fourth = 13.0 to 16.0 mm.
took place soon after the larvae were col- Head capsule: Prognathous, small, sub-
lected. No special requirements were nec- cylindrical, twice as long as wide (Fig. 2);
essary for pupation. Several males and one retractile within the thorax. Head capsule
female emerged from the pupal exuviae. not fused ventrally (Fig. 3). Labrum and
VOLUME 100, NUMBER 3 423
posterior to base of antennae. Epipharynx
formed by two oval plates covered by trans-
verse rows ofmicrotrichiae, and an anterior
brush of long, slender setae that project past
labroclypeal margin.
Antenna: Three-segmented, partially re-
tractable within membranous base (Fig. 4);
originating on latero-apical edges of Head
capsule. Basal segment widest, attached to
membranous base, carrying five long sub-
apical setae distributed as follows: two dor-
sal, two ventral and one lateral; several oth-
er short setae also on dorsal and lateral sur-
faces. Second segment as long as first, nar-
rower, with four long subapical setae,
carrying a large globular sensorium, half
length of third antennal segment (longer in
first instar larva). Third segment much
smaller, with several short setae and a pair
of small cuticular projections.
Maxilla: Elongated, closely attached to
labium, forming an homogeneous structure
loosely connected to head capsule (Fig. 3).
Cardo narrowly subquadrate, covered by
dense pubescence. Stipes as an elongate tri-
angle, broader on distal end, ventral surface
more sclerotized than dorsal, which is in-
completely sclerotized (Fig. 6); galea two-
segmented, basal segment short, distal seg-
ment carrying several short setae and one
long apical seta that reaches base of last
Fig. 1. Pynulomena hurccilis, fifth instar larva, palpal segment; lacinia reduced, appearing
habitus. Scale bar = 5.0 mm. as a thick brush of cuticular spines, cover-
ing base ofgalea and inner margin ofstipes
(more reduced in first instar larva). Palpus
clypeus fused. Head with 3 internal ridges, four-segmented, basal segment largest, as
1 along middle of head, extending almost long as otherthree combined, with two ven-
to distal edge; 2 lateral ones originating be- tral setae; second and third segments short,
hind inner margins of antennae, extending wider than long, second segment with two
back and disappearing at basal third ofhead long dorsal setae and third segment with
capsule. Epicranial suture, in fifth-instar lar- one dorsal and two lateral long setae; distal
vae, present as a fine line, V-shaped, ex- segment subconical.
tending forward from base of middle inter- Mandible: Symmetrical, strongly falcate,
nal ridge to base of lateral internal ridges; with an inner channel opening subapically
non-functional (head capsule not split open on outeredge (Fig. 5). Retinaculumpresent,
between last larval instar and pupal stage). forming a sharp inner tooth on basal third
Occiput forming a V-shaped incision dor- of mandible, with several sharp, short, tri-
sally, from where median internal ridge angular spines. Ventral surface ofmandible
originates. One pair of lateral stemmata. with a dense brush of slender spines pro-
424 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
mm^.'^4^.' 5.,'F^iLft/h'i>n™s'ta"r""l^ar'v"a'.'4","•L^e"f''t'-anhteeanndao,fdfoirfstahlmsvtiaewr.la5r,vaL.ef2t.mDaonrdsiabllev,iedwo.rs3.alVevniterwa.lSvciaelwe.bSacrasle=ba0r.2=mm.5
VOLUME 100. NUMBER 3 425
Figs. 6-8. Pyraclomena horealis. fifth instar liirva. 6, Let! maxilla, dorsal view. 7, Prementum and labial
palpi, dorsal view. 8, Detail ofthe cuticular granules. Scale bars: Fig. 6 = 0.2 mm. Fig. 7 = 0.1 mm.
jecting mediad; dorsal surface with several segmented; basal segment longer and pro-
short setae. One clear, hyaline, long seta or jecting further than second, second segment
sensory appendage close to outer margin of attached to basal half of first one (Fig. 7).
mandible, just before channel opening car- Thorax: Three-segmented. Prothorax
rying several small distal spines. subtriangular, wider at base, containing re-
Liibium: Closely attached to maxilla; tracted head when larva in repose. Meso-
formed by a short and strongly sclerotized and metathorax subrectangular. Thoracic
prementum, an elongated and poorly scler- tergites subdivided by a sagittal line. Color
otized mentum, and a small subtriangular pattern variegated, ranging from light yel-
submentum. Prementum, in ventral view, low to dark brown (Fig. 1). All three seg-
with a distal apical cleft (Fig. 3) and a pair ments with pleural areas formed by an up-
of long and slender setae; in dorsal view per laterotergite, below it an epimeron and
with a group of small, apical cuticular episternum separated by a deep pleural su-
spines and several short setae. Palpus two- ture; mesothoracic laterotergite subdivided.
426 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
anterior plate smaller, carrying mesothorac- brown longitudinal bands in disk. Meso-
ic spiracle. Prostemum large, subpentagon- and metanota shorter, subrectangular, car-
al; meso- and metastema smaller, narrow, rying wingpads on sides and slightly darker
subdivided into an anterior basistemum and than pronotum. First and second pairoflegs
a posterior stemellum. A long and soft fully visible in ventral view; third pair of
neck, with two pairs of long and narrow legs partially covered by wingpads.
sclerites (one dorsal and one ventral), con- Abdomen: Segments wider than long,
nects head with prothorax; head retracts light brown. Tergites one to seven similar
completely within this neck. One pair ofbi- in shape but becoming narrower after ter-
forous spiracles present on mesopleura. gite three; subrectangular, with acute pro-
Legs: Five-segmented, coxae long and jections on postero-lateral comers, and be-
cylindrical; trochanters small, subtriangular coming smaller toward abdominal apex.
in lateral view; femora long and cylindrical; Stemite one covered by legs and wingpads,
tibiotarsi as long as femora, tapering to- segment two partially visible, remaining
wards distal end; pretarsi strong, simple, sternites fully visible. Segment eight small,
with a pair of stout setae at base. Femora partially visible in dorsal view, tergite with
and tibiotarsi with a double row of strong a short acute projection on each posterolat-
setae on inner margin. eral comer.
Abdomen: Ten-segmented, segments one Spiracles: Seven pairs offunctional spir-
to eight similar in shape, becoming narrow- acles; first in pleuron of mesothorax, re-
er towards end; each tergite subrectangular, maining six on abdominal segments two to
divided by a sagittal line, with a lateral pro- seven.
jection on each side pointing backwards
(Fig. 1); ninth segment much smaller, sub-
Biology
quadrate, lacking sagittal line and without
lateral projections; segment ten as a narrow The following description of the life cy-
ring surrounding anal region, carrying hold- cle of Pyractomena borealis was obtained
fast organ. Pleural areas well developed, from specimens collected in the field and
segments one to seven subdivided, upper reared in the laboratory. In many cases,
plate large, suboval, carrying spiracles, specimens reared in the laboratory may
lower plate small, narrowly subtriangular; have different developmental times than
pleura eight with only one suboval plate those living in natural habitats due to
carrying a spiracle; pleural areas of seg- changes in the lightidark cycle (Buschman
ments nine and ten reduced. Abdominal 1977, personal observations). In any case,
sterna large, subquadrate. narrowing to- P. borealis seems to be an annual species
wards end of abdomen. Color pattern sim- and. in Ohio, adults are collected in the
ilar to that of thorax, variegated. Biforous spring. Green (1957) collected pupal exu-
spiracles present on pleu—rites one to eight. viae in May (Minnesota), and April (Mary-
Description of pupa. Slightly curved, land); these agree with our dates for Ohio.
ventrally concave; young pupa light brown In the same paper Green lists the collection
in color, mature pupa darker. Length: 19.0 dates for adult specimens in several states,
to 23.0 mm. all ranging from March (southern states) to
Head: Completely covered by pronotum July and August (northern states and Ca-
in dorsal view (Figs. 9, 10), light brown. nadian provinces).
Eyes large, on sides of head; antennae in- Several mature larvae were collected, on
serted in front of eyes, closer to center of the bark of trees at heights of 2 to 5 feet
frons; anteima and mouthparts dark brown. above the ground. They did not feed, sug-
Thorax: Pronotum large, subtriangular, gesting that they eitheroverwintered as ma-
covering head; light brown with two dark ture fifth instar larvae or prepupae. The lar-
VOLUME 100. NUMBER 3 427
Figs. 9-10. Pyraclotnena horealis. pupa. 9, Ventral view. 10. Dorsal viev%. Scale bar = 5.0 mm.
vae were very active, and they pupated five proached by males soon after emergence,
to six days after being brought into the lab- and her cuticle was not completely sclero-
oratory. Prepupae attached themselves to tized during copulation. Eggs were laid
the bark using the holdfast organ, pupating three to four days after mating, in cracks of
exposed instead ofdigging a pupal chamber the bark or under pieces of bark. The only
as do many other lampyrids, as has also clutch of eggs obtained consisted of ap-
been reported by other authors (Balduf proximately 100 eggs.
1935, Buschman 1977. 1984, LaBella and First instar larvae emerged one month af-
Lloyd 1991). The prepupae, and latter the ter the eggs were laid. Larvae of all instars
pupae, hung vertically, with the head point- fed on snails. Aquatic snails of the genera
ing downward and the venter facing the Physa Drapamaud and Gyraiilus Agassiz
bark. The larval skin remained attached to were used in the laboratory. Early instars to
the substrate, surrounding the terminal ab- the third, showed gregarious feeding habits.
dominal segments of the pupa. Adults Small groups of three to six larvae were
emerged in 4 to 5 days. Males were first to seen feeding together on the same prey.
emerge. The only female reared was ap- Since larvae have a protractable head and a
428 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
280
1
50-
45-
E = eggs
40- LI = larva 1
L2 = larva 2
35- L3 = larva 3
—n= 108 L4 - larva 4
C/3 30- i L5 = larva 5
m
3
P - pupa
c 25-
4«-rf
D
Fig. 1L Mean dunitiiin (in days) ofthe preimaginal stages ofPyiuctomena boicaln (n numberoflarvae).
Duration ofthe fifth instar is approximate.
long neck, up to twice the length of the The duration ofeach stage was very con-
head, they can extend it forward and eat the stant between larvae and is summarized in
contents of retracted snails. They also in- Fig. 11. First and second instars moulted
jected extraoral digesting fluids through after 9 to 1 1 days. The duration of subse-
their mandibles. After feeding they used the quent instars increased with age: third instar
anal holdfast organ to groom their heads, larvae 12 to 13 days, fourth instars 16 to
mouthparts, and neck. Before moulting to 18 days, and, fifth instar larvae were fixed
the next instar, larvae stopped feeding and after about 40 or 50 days. The approximate
hung themselves from the bark or walls of duration ofthe fifth instar, based on the date
the container using the holdfast organ, sim- when the larvae at Cedar Bog were col-
ilar to what they did between the prepupal lected, would be around 280 days. This spe-
and pupal stages. The holdfast organ was cies has five instars (under laboratory con-
also used to aid locomotion while wander- ditions), and the last instar seems to be the
ing around on the bark. one that overwinters. We have no infor-
VOLUME 100, NUMBER 3 429
r^-
HP
10th
segment
lOth
13
segment
MF
14
10th
16
segment
10th
segment
Figs 12-16. Schematic representation of the evenion process of the holdfast organ; see text for a detailed
description. 12, Holdfast organ retracted. 13, First step of the process due to hacniolyniph pressure (HP). 14,
First branching ofthe holdfast organ, the internal muscle fibers (MF) are attached to the end of the finger-like
appendages. 15. 16, Schematic representation oftheevertion processofthe holdfastorgan; seetext foradetailed
description. 15, Holdfast organ completely everted due to haemolymph pressure (HP), the cuticular hooks (H)
cover the distal two-thirds ofeach finger-like appendage. 16, Detail ofone finger-like appendage with internal
muscle fiber (MF) responsible for retraction ofappendage.
mation on where the larvae overwinter, but lampyrid larvae (within the elateroid lin-
it may be among plant debris at the base of eage), being absent in related families. Sim-
the trees. ilar structures are present in some carabids
and staphylinoids (Silphidae). but these
Functional Morphology of the seem to be convergencies. As mentioned
Holdfast Organ
above, the holdfast organ has different
The holdfast organ (also called caudal functions: aiding the larvae in locomotion;
appendage, caudal grasping organ, and tail cleaning their heads and mouthparts after
organ) has been mentioned or described by consuming prey; and attaching themselves
several authors (Targioni Tozzetti 1866, to the substrate between moults and during
Bugnion 1922. 1929, 1933, Blair 1927, the pupal stage.
Okada 1928, Balduf 1935, Peterson 1951, This organ is composed of a series of
Costa et al. 1988. LaBella and Lloyd 1991, eversible, digitiform structures that project
Tyler 1994), and it seems to be unique to from the membranous area of the last ab-
430 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
dominal segment (10th), surrounding the ogique de la France et de la Belgique 67: 461-
473.
anal region. There are five such structures
Buschman. L. L. 1977. Biology and bioluminescence
on each side of the tenth segment. Figures ofselected fireflies in three genera: Pyractomena.
12-16 show a schematic representation of Photinus and Pboluris (Coleoptera: Lampyridae).
the eversion process of one such structure. Ph.D. Thesis, LIniversity of Florida, Gainesville.
The finger-like appendages first appear as a 182 pp.
single tube when they begin to evert (Figs. Buscthommaenn.aL.hicLi.fe1r9a84(.CoBlieoolpotegrya:ofLtahmepyfinrdefaley)P.yrTahce-
12, 13), via haemolymph pressure (HP). As Florida Entomologist 67(4): 529-542.
evertion proceeds, these tubes fork once Costa, C, S. A. Vanin and S. A. Casari-Chen. 1988.
(Fig. 14), and then a second time (Fig. 15); Larvas de Coleoptera do Brasil. Museo de Zool-
ogia, Universidadede SaoPaulo, 282pp.. 165 pis.
this produces four terminal processes, each Green, J. W. 1957. Revision ofthe Nearctic speciesof
one covered on its terminal two thirds with Pyractomena (Coleoptera: Lampyridae). The
microscopic hooks (H). These hooks point Wasmann Journal of Biology 15(2): 237-284.
outwards and forwards, and attach easily to Haddon, K. 1915. On the methods of feeding and the
mouth-parts ofthe larva ofthe glow-worm (Lxim-
any substrate on which the larvae walk.
pyris nacticula). Proceedings of the Zoological
They are also useful for removing mucus Society of London 1915: 77-82.
and other residues left on their head, Hess, W. N. 1920. Notes on the biology ofsomecom-
mouthparts, and neck after feeding on mon Lampyridae. Biological Bulletin 38: 39-76.
snails. This last function is extremely im- LaBella, D. M. and J. E. Lloyd. 1991. Lampyridae,
pp.427-428. In Stehr. F. W.,ed.. ImmatureInsects.
portant since the head is usually retracted Volume 2, Kendall Hunt Publishing Company.
within the prothorax, and any dirt or sticky Dubuque, Iowa, 974 pp.
residue would affect this retraction. McLean, M.. J. Buck, and F E. Hanson. 1972. Culture
On the inside of each of these caudal fil- and larval behavior of photurid fireflies. The
American Midland Naturalist 87(1): 133-145.
aments is one muscle fiber (MF) (Figs. Okada, Y. K. 1928.TwoJapaneseaquaticGlowworms.
14,16), which is responsible for the retrac- Tran.sactions of the Royal Entomological Society
tion of each finger-like appendage. During ofLondon 76(1): 101-108. 1 pi.
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backwards, thus avoiding being caught on to Nearctic species. Part II. Coleoptera. Diptera.
Neuroptera. Siphonaptera, Mecoptera, Trichop-
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