Seed feeding by a multispecies swarm of flea beetles (Coleoptera: Chrysomelidae: Galerucinae: Alticini)

3 Pages·2001·1.4 MB·

by  R W Flowers

:
PROC. ENTOMOL. SOC. WASH.
103(1), 2001, pp. 257-259
Note
Seed Feeding by a Multispecies Swarm of Flea Beetles
(Coleoptera: Chrysomelidae: Galerucinae: Alticini)
The large and colorful flea beetle Omo- tirely of O. aequinoctialis; about ten per-
phoita aequinoctialis (L.) is a familiar sight cent were Asphaera nobilitata (Fabr.) and a
in many Central American habitats, from single individual of Omophoita championi
forest edges and clearings to agricultural ar- Jacoby was also observed. The Asphaera
eas. However, despite its abundance, very were also seen seeking out and feeding on
little is known ofits life cycle and behavior. Aegiphila seeds. Both Asphaera and Omo-
In July 1999, a large swarm ofthese beetles phoita belong to the subtribe Oedionychina
was encountered in a forest fragment in within the Alticini, and are probably con-
southern Costa Rica at the Wilson Botanical generic, although no phylogenetic analysis
Garden, Las Cruces, Puntarenas Province. has yet been attempted. Fifteen specimens
The beetles were concentrated along a short of O. aequinoctialis were collected and are
length of trail, and many were seen briefly deposited as vouchers in the Instituto Na-
alighting on the leaves ofunderstory plants. cional de Biodiversidad (INBio) in Costa
No feeding was apparent on any of these Rica.
plants; their only use by the beetles was for Despite its abundance in CentralAmerica
brief rest periods. Many other individuals and northern South America, there are ap-
in the swarm were seen crawling on the sur- parently no explicit host plant citations for
face of the leaf litter on the trail, or flying O. aequinoctialis. In his description of O.
just above the ground. At the slightest dis- punctulata, Bechyne and Bechyne (1963.
turbance, most of those on the ground also Beitrage zur Kenntnis der Salvadorischen
—
took wing and flew back up to the under- Chrysomeloidea. Iheringia Zoologia 31
story plants. The beetles in the leaf litter 62) reported that species as "found on Ver-
were observed feeding in the interior of benaceae". Jolivet and Hawkeswood (1995.
broken seeds (Figs. 1, 2). These seeds, Host-plants of Chrysomelidae ofthe world.
which were abundant in the litter along a Backhuys Publishers, Leiden. 281 pp.) re-
m
20 stretch ofthe trail, came from a single ported the genus Omophoita as associated
canopy tree which was identified as Aegi- with Verbenaceae, but without giving any
phila anomala Pittier (Verbenaceae). Seen specific references. On the other hand, a
from the ground, there appeared to be nu- third species, O. simulans Jacoby, has been
merous seedpods on the branches of the observed feeding on Convolvulaceae, as
tree, but few intact seedpods were on the has A. nobilitata (Flowers and Janzen,
ground and all those were very old and de- 1997. Florida Entomologist 80: 334-366).
cayed. Seeds of this tree, however, have The three Omophoita species aequinoctial-
very hard coats and persist after the rest of is, punctulata, and simulans are all very
the fruit has disappeared. Most ofthe seeds similar in appearence, differing only in
had large holes or were broken in half. In punctation and the shape ofone ofthe pairs
contrast to the apparent nervousness of the of elytral spots.
beetles perched on plants or crawling on top Except for the subfamily Bruchinae
of the leaf litter, beetles actively feeding in- (whose larvae feed on seeds), feeding on
side the seeds were not readily disturbed seeds by any of the Chrysomelidae has not
and fed for several minutes at a time. been previously reported. However, the as-
The beetle swarm was not composed en- sociation of the Las Cruces swarm with
258 PROCEEDINGS OF THE ENTOMOLOGICAL SOCIETY OF WASHINGTON
Verbenaceae is consistent with what Httle 14: 5-274; Flowers et al. 1994. Coleopter-
has been reported in the literature concern- ists' Bulletin 48: 79-89; Flowers and Jan-
ing the host plants of Omophoita. The Ae- zen 1997) and Alticini (Flowers and Tiffer.
giphila tree that produced the seeds had rel- 1994. Brenesia. 37:135-136). Here the ac-
atively few leaves, and these were all full tivity is apparently a part of mating behav-
of small holes consistent with Alticini feed- ior, although feeding by individuals not ac-
ing damage. Due to the height of the tree, tively copulating can result in substantial
it was not possible to see if there were any plant damage. Taxa where this form ofmat-
insects feeding on the leaves at the moment. ing behavior has been observed include the
Gregarious behavior in leafbeetles is not Clytrini genera Anomoea (Flowers et al.
uncommon and usually involves groups of 1994), Babia (Flowers and Janzen 1997),
adults and/or larvae exploiting a single or a Megalostomis, and Temnodachrys (Monros
group ofhost plants. Resulting aggregations 1953), and an unidentified species in the
are generally modest in size and involve a monoplatine flea beetle genus Hypolampsis
complex interplay of beetle responses to (Alticini; Flowers and Tiffer 1994).
conspecifics, to their host plants, and ten- The swarming in Omophoita and As-
dencies to random movements (Morris et al. phaera observed at Las Cruces does not fit
1996. In P. H. A. Jolivet, and M. L. Cox, into any of the types of gregariousness
eds., Chrysomelidae Biology Volume 2: known to date in the Chrysomelidae. No
Ecological Studies. SPB Academic Publish- mating activity was observed, and the seed
ing, Amsterdam, The Netherlands, pp. 303- feeding was well outside the normal leaf
322.). However, two species ofthe fleabee- feeding behavior ofAlticini. A furthercom-
tle genus Macrohaltica (Galerucinae, Alti- plicating aspect is that while beetles were
cini) form stable aggregations of as many seen feeding on opened seeds, none were
as 5,000 individuals which move together seen chewing through the seed hulls. Thus,
from one food plant to the next, as well as the opened seeds could have been a bonan-
staying in non-feeding swarms (Eberhard et za for the beetles inadvertently provided by
al. 1993. Psyche 100: 93-119). In some some vertebrate, possibly a rodent (Luis Di-
Cassidini and Chrysomelinae, larvae form ego Gomez, personal communication), and
defensive aggregations, a phenomenon the beetles may have been opportunistically
called cycloalexy (Vasconcellos-Neto and feeding on a part of their normal host plant
Jolivet. 1988. Bulletin de la Societe ento- that is not normally accessible. Such op-
mologique de France 92(9-10): 291-299), portunistic feeding in Chrysomelidae has
while in a number of species the females also been observed in another flea beetle
stay with and protect their larval broods which feeds on Euphorbia elata (Euphor-
(Jolivet. 1999. In M. L. Cox, ed.. Advances biaceae). If a stalk of this plant is broken,
in Chrysomelidae Biology 1. Backhuys the sap flowing from the cut stem rapidly
Publishers, Leiden, pp. 391-409; Windsor attracts large numbers of Centralaphthona
and Choe. 1994. In R H. Jolivet, M. L. Cox, nr. lessmanni Bechyne & Bechyne (Chry-
and E. Petitpierre, eds.. Novel Aspects of somelidae: Galerucinae: Alticini; Flowers
the Biology of the Chrysomelidae. Kluwer and Janzen 1997). It appears that in at least
Academic Publishers, The Netherlands, pp. these few chrysomelid species, secondary
111-117). Other Cassidini also form aggre- plant compounds in parts other than leaves
gations during dormancy in tropical dry can stimulate strong feeding responses, en-
forests (Flowers. 1991. Biotropica 23: 308- abling the leaf beetles to occasionally ex-
310). ploit non-leaf parts of their host plants.
Swarming behavior with a different ob- I sincerely thank Dr. Luis Diego Gomez
jective has been documented in the Clytrini and the staff of the Las Cruces field station
(Monros. 1953. Acta Zoologica Lilloana for their assistance and hospitality, and Dr.
VOLUME NUMBER
103, 1 259
Figs. 1-2. Omophoita aequifwctialis. 1, On seeds oiAegiphila anomiila. 2, Feeding inside seed ofA. an-
omala.
Barry Hammel (Missouri Botanical Gar- CSREES, USDA, to Florida A&M Univer-
den) for his help in identifying the plant. I sity.
also thank the staff of INBio for transpor-
tation and other assistance during this pe- R. Wills Flowers, Agricultural Research
riod. This research was supported in part by Programs, Florida A&M University, Tal-
grants from INBio and the Biodiversity Re- lahassee, FL 32307, U.S.A. (e-mail:
sources Development Project, GEFAVorld [email protected])
Bank, and by a grant (FLAX 91005) from