NEST STRUCTURE OF A Euglossa sp. N. IN A FRUIT OF Theobroma subincanum FROM ECUADOREAN

AMAZONAS.

Jens Mogens Olesen (*)

INTRODUCTION

Nests of euglossine bees are rarely found. The nest structure is only known for

about 15¾ of the species (Dressier, 1982).

Here I describe the nest structure of an Amazonian Euglossa sp. The species isun

described, but closely related to E. charapensis (Dressier, pers. comm.). A description

of the species has to await a collection of males. Bee voucher specimens (JMO 2 3 1 * 0 are

deposited at Dressier, R. L., Florida State Museum, and at The Natural History Museum,

Aarhus, DK.Plant specimens (*623^0, JMO ̂ 1 3 7 ) are depos i ted at The Herbarium Jutlandicum,

Aarhus, DK.

Study Area

The observations were made in the tropical lowland rainforest, 2 km S of anangu at

Rio Napo, YasunT National Park, Ecuador ( 0 0 ° 3 2 ' S , 76 ° 2 6'W) about 300 m a.s.l. during

April 1 9 8 6 . The nest site was located on a ridge in the non-flooded terra firme forest.

The daily temperature fluctuates between 21°C and 2 8 ° C , and the air is almost saturated

with humidity. The site was described in detail in Balslev et a]. ( 1 9 8 7 ) .

Generally the bee fauna in the area is very poorly known. Besides the undescribed

Euglossa sp. of this study I observed bees belonging to the Eulaema bombiformis complex

(Dressier, 1979; Janzen, 1983). During three days males were observed performing their

special display behaviour at two young trees ( 1 5 cm dbh) both in the terra firme and iη the várzea forest. At the tree in the várzea, up to three males were observed at a time. They flew towards the trunk, where they moved up and down. Suddenly they landed on the surface of the trunk, curved their body, lifted the wings above the thorax, grabbed hold of the bark with their mandibles and made a high buzz. This behaviour has been described in detail (Dressier, 1982; Janzen, 1983). They often flew towards me when I approached, hovering for a few seconds in the air 30-40 cm in front of my face. A fema 1e was observed twice at a small pond in the forest collecting mud. A colony of Bombus transversal is (Olivier) was located (Olesen, in press). Males of E. ignita were seen several times at inflorescences on the understory palm, Geonoma macrostachys Mart. Species of Xylocopa and Centris and several minor bee species, e.g. Trigona, were observed too.

(*) Botanical Institute, University of Aa r h u s , Nordlandsvej 6 8 , DK-8240. Risskov, Denmark.

ACTA AMAZÔNICA, 18(3-4): 3 2 7 - 3 3 0 . 1 9 8 8 . 3 2 7

RESULTS AHD DISCUSSION

A Guglossine nest was found inside an old fruitcaught in the understory vegetation about 30 cm above ground level. It is unknown whs t her the f ru i t had d ropped f rom the tree before or after the nest was established. The fruit belonged to Theobroma sublncanum Mart. (Sterculiaceae) (Figs. 1 , 2 ) , an understory tree about 8 m iη height and about 15cm

in dbh. The outer fruit wall was intact. When the fruit was opened two female euglossines were seen walking around on the

cells, a third one escaped, and a dead headless one was found in the nest also. Description of female: Total length 1 2 . 5 n;m; head width ^ . 8 mm; abdominal width

5,3 mm. Colour: Paraocular white markings lacking; without white marks on antennal scapes; front of clypeus green with dark carina; paraocular area b1ue-green; frons blue-green; episternum shiny blue; scutum blue; scutellum blue; abdomen bronze above, green and dark ventrally; hind tibia blue. Vestiture: Hairs of thorax dark; white and dark hairs on clypeus; hairs of vertex long and dark; white hairs on abdomen becoming longer posteriorly. Punctation: Coarse and shallow on clypeus; coarse, dense and deep on epis­ternum; on scutum, dense and of varying size; on scutellum, dense and becoming coarser posteriorly; on tergum 2 , very small puntaction. Tongue about 11 mm long; mandibles tr_i_ dentate; labrum wider than long with prominent median keel and shorter lateral keels; clypeus protuberant, with prominent median and lateral keels; scutellum about half as long as wide, posterior margin nearly straight medially.

The dimensions of the fruit were about 9 cm χ 5 cm χ cm. The fruit was without any of its original content. Its wall was about 1 mm thick. An entrance hole withad_i_ ameter of 5 . 5 mm was found 8 - 9 mm from the apex of the fruit (Figs, la, 2 ) . The entrance pointed downwards and was on its inner side lined with a 3 urn high wall of resin. The fruit was not lined with resin. A twig and a few pieces of leaves were build into the cells. The cell cluster was made of dark resins and had the dimensions 5.0 cm χ ^ , 5 cm x J.5 cm (Figs, la, 2 ) ,

Twenty-four old cells ans 13 sealed ones were arranged i n e g u l arly i η three stories in the colony (Figs, la, 2 ) , but the long axes of most eel 1 s were more or less vertical. Three of the closed brood cells were empty, seven contained a 1arva and three a pupa. The dimensions of the cells were 15 mm χ 1 5 inn χ 1 1 mm. The walls were shared more or less Jointly by neighbouring cells.

On the day after the nest had been removed one bee was observed at 10. 15 h, and later two bees were obserbed at }0.^+Sh flying around exactly at the position in the air where the fruit had hung. One of them was caught. So totally the nest contained 3-Ί living females and a dead one, probably the foundress,

The species was observed collecting pollen from shrubs of Bixa orclIana L. (Fig. 1c) along the banks of Rio Napo together with many other bee species.

The Euglossini are the most primitive group of apine bees, and like virtually all pther bees they are solitary or parasocial. Al though n^any eug 1 oss i nes a re sol i ta ry, para_ sociality is well-known in some species (Sakagami et al., 1967) - The species studied here

328 Olesen

w i t h r- .ore t h a n o n e f e m a l e i n t h s s ^ m e n e s t m a y t h u s b e r e g a r d e d a í p a r o s o c i a l ,

ACKNOWLEDGEMENTS

I v j i s h t o i i x p r e s s my t h a n k s t o D r . R o b e r L L . D r d i s l c r f r o : n t h e U n i v e r s i t y o f F l o ­

r i d a f o r h i s i π f o r . .:, L i o n a b o u t t h e b e e s a n d t o D r . H p r i r i k G a l s l e v f r o f i t h e U n i v e r s i t y

o f A a r h u s f o r i d e n t i f i c a t i o n o f t h e ρ 1 a n t s p e c i e s a n d f o r m a k i Jig my s t u d i e s a t A n a n g u p o s s i

b l e . T h i s p a p e r E c u a d o r P r o j e c t C o n t r i b u t i o n n o . 9 6 , A a r h u s U n i v e r s i t y , D K ,

SUMMARY

Λ rateai a\ LTM uncfij-àcTÁbta' ipucxej Euçfloòia κν,-Ί found òiiide, a {liUS c<: Theobiwma.

iubincamun \$£eAiu£LC(íie'At.] i'n thi fauzoníait fàÁMfò/ieÁ.t, í-cuüdüi. It contaiin'd 1-4 íivr,\q

\íma.t<u, and me. dead ami 37 r »·<".·:'j ó i a?» . Total Zcf.qth o j f>«c /!. Sniir á-lojU büuc- ο·Ίυ%·Ί;

Viiu-'iiU £u '«c; uòdfw.Ji biattzÇ ttbavtj giecn and datii υαι/Λαίίιΐ; atuí kiwi tíbia bZiw. TotigyA

çhoiU 1J .'riii to Μ_<j.

Κ i j » . I . A . N e M ' • 1 E u g l o s s a S p . n . i n i i d t ' .r f r u i t u í T l iüobroíjki a i ib incinum . Thr.> i r r o w i f l r t i

r j j r ' e a ι h. , ? n t r . m c e i i o l t . ( T l i e w h i t e t h r e a d s m i the c . c l 1 a a r c r e u n i i n s f r o m c o t t o n

u o o l u s o d f o r t r a n s p o r t a t i o n ) . Κ . T w o Let ( i m p l y f r u i t s o f TticDbrociLii ftubincatiiini

í o l í u C t o d f r o m rj r n . - L ' , C . Λ f t m s l e ü F chr> E u g l o s s a s p . η , e i t h e r ! t ig p o l ] ι·τι £ ro r , i

B i x i i orc l I .Tna r l a s u t'.> R i o ? i a p ü .

N t'SL S t 'ΓΜί.'ίιι re m"

fruit

2cm ent rance hole F I R . 2 , B r o o d c e l l s o f t h e Euglossa s p . n . i n s i d e t h e f r u i t of Theobroraa subiccanum.

References

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( A c e i t o p a r a p u b l i c a ç ã o e m 1 9 . 1 0 . 1 9 8 8 )

330 01 e s e n