McMullen, Conley K.

English

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16 NOTICIAS DE GALAPAGOS No. 48 
THE GALAPAGOS CARPENTER BEE, 
JUST HOW IMPORTANT IS IT? 
By: Conley K. McMullen 
The presence of the 
endemic Galapagos 
carpenter bee (later to be 
called Xylocopa darwini 
Cockerell) was first 
reported by Fredrick 
Smith in 1887 (Linsley et 
al. 1966). By the early 
1900s, this bee was known 
to be well represented 
among the Islands of the 
Archipelago, especially in 
what would now be 
considered the littoral and 
arid vegetation zones. 
Williams (1926) noted 
that it used the wood of 
primary pollinator was 
obtained during a trip to 
Galapagos in August of 
1988. I observed the 
carpenter bee visiting the 
flowers of several plants 
on Santa Cruz, but few 
other insect pollinators 
were seen. In fact, only 
Phoebis sennae 
(pieridae), the Galapagos 
sulfur butterfly, and 
Leptotes parrhasioides 
(Lycaenidae), the 
Galapagos blue butterfly, 
were observed, and these 
A GaJapagos carpenter bee visiting a hibiscus (Hibiscus tiliaceus) 
flower. Una abeja carpentera visitando elflor de peregrina 
(Hibiscus tiliaceus). 
only rarely. The list of 
plants visited by the Galapagos carpenter bee, along 
with the resident status of each, is in Table 1. The 
majority of these observations took place along the 
road from the Darwin Station to Bella Vista in the 
arid and transition vegetation zones. However, the 
Hibiscus tiliaceus was located in the littoral zone at 
the Darwin Station; and the members of Acacia 
insulae-iacobi (Mimosaceae), Cassia picta 
(Caesalpiniaceae), andLycopersicon cheesmaniivar. 
cheesmanii (Solanaceae) that were seen being visited 
by this bee were located along the road in the arid 
zone on the north side of Santa Cruz. The carpenter 
bee was seen pollinating flowers of Parkinsonia 
aculeata (Caesalpiniaceae) and Waltheria ovata 
(Sterculiaceae) in the arid zones on both the south 
and north sides of Santa Cruz. 
Hibiscus tiliaceus (Malvaceae), Croton scouleri 
(Euphorbiaceae), Bursera g raveolens (Burseraceae), 
and Erythrina velutina (Fabaceae) for nesting 
purposes. Because of this habit of nesting in wood, 
it was hypothesized that the carpenter bee may have 
initially reached the Archipelago in a drifting log 
(Cockerell 1935). 
Since these early reports, only a few studies have 
been conducted to determine the carpenter bee's 
distribution and role in the Galapagos. However, by 
1981 it had been recorded on the Islands of Baltra, 
Daphne, Espanola, Floreana, Gardner (near 
Espanola), Isabela, Pinz6n, San Cristobal, Santa Cruz, 
Santa Fe, and Santiago (Linsley 1966, Linsley et al. 
1966, Grant and Grant 1981). It was found to nest in 
Scalesia affinis (Asteraceae), May tenus octogona 
(recorded as M. obovata; Celastraceae), and Castela 
galapageia (Simaroubaceae) (Linsley et al. 1966) as 
well as those species already mentioned by Williams. 
Studies by Linsley (1966), Linsley et al. (1966), Rick 
(1966), and McMullen (1985, 1986, 1987) have also 
suggested that this bee is undoubtedly responsible 
for the vast majority of insect pollination that takes 
place in the Archipelago. 
Additional support for the role of X. darwini as 
Since most of these were casual observations, a 
comment on the usual level of visitation activity 
would be difficult to make. However, there were two 
species thatX. darwini appeared especially attracted 
to and visited daily. These were P arkinsonia aculeata 
and Hibiscus tiliaceus. Pollen from these plants was 
clearly visible on the abdomen of bees that visited 
them. When visiting H. tiliaceus, each bee would 
enter a flower and work its way around the staminal 
December 1989 NOTICIAS DE GALAPAGOS 17 
Table 1. Summary of flowers visited by the Galapagos 
carpenter bee (Xylocopa darwini) on Isla Santa Cruz, 
11-28 August 1988. 
Family Species Statusl 
Asteraceae Sonchus oleraceus IW 
Boraginaceae Cordia lutea N 
Caesalpiniaceae Cassia picta N 
Caesalpiniaceae Parkinsonia aculeata N 
Convolvulaceae Ipomoea linearifolia E 
Malvaceae Bastardia viscosa N 
Malvaceae Hibiscus tiliaceus N 
Mimosaceae Acacia insulae-iacobi N 
Nyctaginaceae Commicarpus tuberosus N 
Passifloraceae P assiflora foetida 
var. galapagensis E 
Solanaceae Lycopersicon cheesmanii 
var. cheesmanii E 
Solanaceae Solanum americanum N 
Sterculiaceae Waltheria ovata N 
Verbenaceae Clerodendrum moUe 
var. glabrescens E 
Verbenaceae Clerodendrum moUe 
var. moUe N 
Verbenaceae Lantana peduncularis 
var. peduncularis E 
1 Status is coded as follows: IW = Introduced Weed, 
N = Native, and E = Endemic. 
column, dusting itself thoroughly with pollen before 
moving on to the next flower (see photograph). 
Most of the species listed in Table 1 have previously 
been reported as visited by X. darwini (Linsley et al. 
1966, Rick 1966, McMullen 1985). However, four 
species represent new records for the Archipelago. 
These are Cassia picta, Ipomoea linearifolia 
(Convolvulaceae), Solanum americanum 
(Solanaceae), and Sonchus oleraceus (Asteraceae). 
All of the bees observed were female, except for 
one male seen visiting Acacia insulae-iacobi and 
another visiting Waltheria ovata. Both of these 
sightings occurred on the north side of Santa Cruz. 
The adult carpenter bee was thought not to have 
any natural enemies in Galapagos (Linsley 1966). 
While observing the male at W. ovata, an event took 
place that was quite unexpected. A mockingbird, 
perched on a nearby tree, flew down and without 
stopping snatched the bee from the inflorescence. It 
then landed, and began to shake the bee and beat it on 
the ground. The bee escaped twice but both times 
was recaptured before being killed, and I assume it 
was eaten although I did not actually see it being 
swallowed. It would be interesting to know if the 
carpenter bee is important to the mockingbird as a 
regular food source. Linsley et al. (1966) mentioned 
that attempts to establish honeybees in Galapagos 
failed, probably as a result of predation by 
mockingbirds. Perhaps this might also help explain 
the absence of the carpenter bee on some of the 
Islands in the Archipelago. 
As mentioned earlier, the Galapagos carpenter 
bee is thought to be the major pollinator in the 
Archipelago. However, it has been hypothesized 
that many of the endemic members of the Galapagos 
flora were present before the carpenter bee arrived; 
and because of this lack of insect pollen vectors, 
these plants are primarily automatic self-pollinators 
and have non showy flowers (Linsley et al. 1966, 
Rick 1966, McMullen 1987). 
I hope to test this hypothesized relationship 
between pollinator presence and plant reproductive 
biology by comparing the results of my earlier work 
on Santa Cruz angiosperm breeding systems 
(McMullen 1987) with future studies of the same 
plant species on another island where the carpenter 
bee is not present. These studies will indicate whether 
or not the carpenter bee has influenced the breeding 
systems and flower characteristics of endemic plants 
on the islands that it inhabits and will add to our 
understanding of its overall importance in the 
Galapagos. 
ACKNOWLEDGMENTS 
I wish to express my gratitude to Gladys Travez, 
Aracelly Fajardo, and Humberto Ochoa for their 
hospitality during my stay in Galapagos. I also thank 
Juan Black, Gayle Davis, Bryan Dutton, Carl Helrich, 
Stan Grove, William Weber, and Goshen College, 
Goshen, Indiana, for their support. 
LITERATURE CITED 
Cockerell, T.D.A. 1935. The Templeton Crocker 
Expedition of the California Academy of Sciences, 
1932. The carpenter bees of the Galapagos Islands. 
18 NOTICIAS DE GALAPAGOS No. 48 
Proceedings of the California Academy of 
Sciences, Fourth Series 21:379-382. 
Grant, B.R., and P.R. Grant. 1981. Exploitation of 
Opuntia cactus by birds on the Galapagos. 
Oecologia 49: 179-187. 
Linsley, E.G. 1966. Pollinating insects of the 
Galapagos Islands. pp. 225-232 In R.I. Bowman 
(ed.) The Galapagos. University of California 
Press, Berkeley. 
Linsley, E.G., C.M. Rick, and S.G. Stephens. 1966. 
Observations on the floral relationships of the 
Galapagos carpenter bee. Pan-Pacific 
Entomologist 42: 1-18. 
McMullen, c.K. 1985. Observations on insect 
visitors to flowering plants of Isla Santa Cruz. I. 
The endemic carpenter bee. Noticias de Galapagos 
42:24-25. 
McMullen, C.K. 1986. Observations on insect 
visitors to flowering plants of Isla Santa Cruz. II. 
Butterflies, moths, ants, hover flies, and stilt bugs. 
Noticias de Galapagos 43:21-23. 
McMullen, c.K. 1987. Breeding systems of selected 
Galapagos Islands angiosperms. American Journal 
of Botany 74:1694-1705. 
Rick, C.M. 1966. Some plant-animal relations on 
the Galapagos Islands. Pp. 215-224 In R.I. 
Bowman (ed.), The Galapagos. University of 
California Press, Berkeley. 
Williams, F.x. 1926. Expedition of the California 
Academy of Sciences to the Galapagos Islands, 
1905-1906. The bees and aculeate wasps of the 
Galapagos Islands. Proceedings of the California 
Academy of Sciences, Fourth Series 2:347-357. 
Conley K. McMullen, Department of Biology, 
Cumberland College, Williamsburg, Kentucky 
40769, USA. 
ISLA SAN CRISTOBAL 
Por: Jacinto Gordillo G. and Arnrit Work Kendrick 
Superficie.-Tiene de superficie 558 km2, 
aproximadamente la mitad del area de la Isla Santa 
Cruz. Solamente tres de las islas del Archipielago 
son mayores en superficie. 
Altura.-Su mayor altura es de 735 m.s.n.m. en 
lacumbre de Cerro San Joaquin, pero la area alrededor 
de este cerro consiste de un volcan grande de 660 
m.s.n.m. promedio por arriba. Para la mitad de la Isla 
al Este, las alturas no pasan 160 m.s.n.m. 
Caracteristicas de Geografia y Geologia.-La 
Isla San Crist6bal (previamente conocido como Isla 
Chatham), como las demas, es de origen volcanico y 
una de las mas viejas de Galapagos. Es la Isla mas al 
Este del Archipielago. Su constituci6n externa, 
revestida en partes de lavafluente decaracterextrusivo 
yen partes de material intrusivo, nos hace pensar en 
varias etapas de formaci6n. De Cerro Brujo hacia el 
Noreste es mas nueva que la del Suroeste, donde 
justamente tiene su asiento la poblaci6n humana. 
Ecologia.-Como otras islas, San Crist6bal tiene 
areas altas con vegetaci6n densa y climas hlimidas y 
areas bajas muy secas. Por influencia de los vientos 
y la forma de la Isla, el Noreste es la mas seca; ademas 
es aislado de las zonas colonizadas. 
Poblacion Humana.-La Isla San Cristobal, a 
pesarde contrarse en el extremo Estedel Archipielago, 
por tanto mas cercana al Ecuador continental, no fue 
la primera en ser colonizada por el hombre, pese a 
que es una Isla mas grande y de mayores recursos 
naturales. Fue ocupada con prioridad la Isla Floreana 
en 1832; pero al fallar los reiterados intentos de 
ocupaci6n agricola en la mencionada Isla, San 
Crist6bal empez6 a servirde refugio a ciertos hombres 
que abandonaban Floreana. 
Muy poco se sabe sobre fechas y nombres de los 
primeros immigrantes; solamente a partir de 1866, 
conocemos con certeza el ingreso del senor Manuel 
Julian Cobos que vin6 con Jose Monroy, con el 
prop6sito de explotar el orchilla (Rochella abintonii). 
Ver folleto "Manuel J. Cobos - Historia de un 
Pionero," por Jacinto Gordillo en Galapagos (1987). 
Ademas desarrollaron una industria de azlicar con su 
propia refineria. 
Al terrninarse el intento de colonizaci6n en la Isla 
Floreana y comenzar Ia ocupaci6n permanente de la 
Isla San Crist6bal, pasaron tambien a esta susderechos 


The Galapagos carpenter bee, just how important is it?

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The Galapagos carpenter bee, just how important is it?

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