Original article A morphological comparison of the dwarf honey bees of southeastern Thailand and Palawan, Philippines TE Rinderer BP Oldroyd S Wongsiri HA Sylvester LI de Guzman JA Stelzer RM Riggio 1 USDA, Agricultural Research Service, Honey-Bee Breeding, Genetics and Physiology Research Laboratory, 1157, Ben Hur Rd, Baton Rouge, LA 70820 USA; 2 Bee Biology Research Unit, Department of Biology, Chulalongkorn University, Bangkok 10330, Thailand; 3 Dept of Entomology, Louisiana State University, Baton Rouge, LA 70893, USA (Received 20 February 1995; accepted 11 April 1995) Summary — Morphological descriptions using measurements common to honey bee taxonomy are pro- vided for Apis andreniformis Smith (1858) from southeastern Thailand and Palawan, Philippines and Apis florea Fabricius (1787) from southeastern Thailand. Overall, A andreniformis has a very different morphology from the sympatric A florea and from all other well-described species of honey bees. One difference, the color of the scutellum, although not species specific, is sufficient in many cases to facilitate field identifications. Very few morphological differences occurred between the Thai and the Philip- pine populations of A andreniformis. Asian bees / Apis andreniformis / Apis florea / morphometry / population genetics / Thailand / Philippines INTRODUCTION study supported the conclusions of Wu and Kuang (1986, 1987) who studied furcated The small dwarf honey bee, Apis andreni- basitarsus differences between drones of formis Smith (1858) has recently been re- A florea Fabricius (1787) and A andreni- evaluated and recognized as a valid bio- formis. A species-specific characteristic of A logical species based on morphological andreniformis identified by Smith (1858) of evidence of a unique endophallus, charac- worker bees having black hairs on the hind teristic worker bee wing venation, and a dis- tibia and dorsolateral surface of the hind tinctive furcation of the male basitarsus basitarsus as opposed to the white hairs of (Wongsiri et al, 1990). The Wongsiri et al A florea was confirmed by these studies. Further confirmation of the valid biological the 2 species are sympatric. Four colonies of A andreniformis were from species status of A andreniformis was pro- sampled Palawan, Philip- an island which is outside the distribution vided by Rinderer et al (1993a) who reported pines, of A florea. Ten workers from each colony were that the of drones from mating flights sym- dissected and 44 morphometric measurements patric A andreniformis and A florea were were made using computer-assisted techniques temporally separate. While these reports (Daly et al, 1982; Rinderer et al, 1993b). These clearly show A andreniformis to be a sepa- measurements and their alphabetical designa- rate species, they do not describe all the tions are given in table I and follow the system of described Ruttner morphological measurements commonly morphometric analysis by et al (1978), Ruttner (1987) and Rinderer et al used in modern bee honey taxonomy (Rut- (1989). Numerical designations for wing vena- This mor- tner, 1987). paper provides these tion angles (fig 1) are a combination of the angles phometric details for 2 populations of A studied by Ruttner et al (1978) and Daly and andreniformis occurring in southeastern Balling (1978) and follow the designations of Thailand and Palawan, Philippines (de Guz- Rinderer et al (1989). For the most part, num- bers represent lengths or widths of various struc- man et al, 1992). tures and are reported in millimeters. Interior Since A andreniformis is most similar to angles of vein intersections in wing venation pat- A florea and since little is known of the inter- terns are reported in degrees. Pigmentation char- species morphological variation of either acteristics of the second, third and fourth tergites, species, comparative data for the sympatric the scutellum, the metanotum and the mesonotum are scored according to the procedures of Ruttner of A florea in Thailand are also population et al (1978) and Ruttner (1987). Scores for ter- provided. gite color intensity range from 0 to 10 with 0 being completely black and 10 being completely yel- low. Scutellum scores range from 0 to 9 with 0 MATERIALS AND METHODS being completely black and 9 being completely yellow. Scores for the color intensity of the metan- otum (B) and the mesonotum (K) range from 0 Twenty-seven colonies of A florea and 18 colonies to 5 with completely black being 0 and completely A andreniformis were sampled in Thailand where yellow being 5. After measurements were made on individ- The 2 populations of A andreniformis dif- ual bees, colony averages for each characteristic fered for only a few characters. The Thai were calculated. These averages were used to A andreniformis had and calculate variances and for each longer forewings means, ranges but fewer hamuli. measurement within each species (table I). The longer hindwings, Wing differences with similar widths colony averages were also used to calculate t- length wing test evaluations of differences between A florea probably led to the 3 observed significant and A andreniformis from Thailand and between differences in wing angles. Thai A andreni- A andreniformis from Thailand and the Philip- formis also had significantly narrower A multivariate discriminant was pines. analysis metatarsi and a scutellum which was, on also conducted to estimate Mahalanobis dis- than that of both A florea tances between population centroids. average, lighter and A andreniformis from the Philippines. A multivariate discriminant analysis of RESULTS data summarizes the population differences. A Mahalanobis difference of 110 252 sepa- rates Thai A andreniformis from Thai A flo- In general, A florea from Thailand are larger rea while a Mahalanobis difference of 2 891 than sympatric A andreniformis. Of the 17 separates Thai A andreniformis from Philip- measurements of length or width involving pine A andreniformis (fig 2). wings, legs, mouthparts and sternites, in only 2 cases was A andreniformis equal to or than A florea. both greater Interestingly, DISCUSSION these cases involved wing length: forewing lengths were about equal and hindwing lengths of A andreniformis were larger. Overall, A andreniformis has a very different The 2 species differed in all the angles of morphology from the sympatric A florea. wing vein intersection save number 40. The color of the scutellum appears to be a Cubital segment A was larger in A andreni- useful field character to identifying A formis and cubital segment B was larger in andreniformis. Additionally, the remainder A florea. Consequently, the cubital index of of the measurements provide a picture of A andreniformis (6.37) was much larger than A andreniformis as a remarkably different that of A florea (2.86). honey bee, unique in its morphological orga- nization. In general, A florea had less black pig- ment on the various structures measured The differences between the Thai and in congruence with the general visual the Philippine populations of A andreniformis impression that A florea are mostly yellow are rather small considering their geo- bees and A andreniformis are mostly black graphical separation. Similar distances with bees. A notable exception to this rule is the geographical isolation result in strong sub- pigmentation of the scutellum. Scutellum specific variation in A mellifera (Ruttner, color for A andreniformis tends toward yel- 1987). However, the differences between low while the scutellum color for A florea the Thai and Philippine populations of tends toward black. The range of A andreni- A andreniformis are less than differences formis scutellum coloration does extend into typically used to support subspecific desig- the black range. However, the range of nations. But the 2 groups show no overlap in scutellum coloration for A florea of our sam- the multivariate discriminant analysis pro- ple does not include yellow. Thus, this highly cedures with each group forming a tight visible character may be useful for field iden- grouping about its centroid. If more sam- tifications of A andreniformis. ples confirmed these observations, the lack of overlap might be interpreted as indicating development of honey bee characteristics subspecific differences (Ruttner, 1987). (Rinderer et al, 1992, 1993a). Much remains to be learned about A andreniformis. Its historical confusion with ACKNOWLEDGMENT A florea has probably resulted in many pub- lished studies on what was actually A andreniformis being reported as informa- This study was made in cooperation with tion on A florea. Clear information on the Louisiana Agricultural Experiment Station. ranges of these 2 species will provide a guide as to which literature resulted from studies of bees in areas of sympatry and Résumé — Comparaison morphologique needs to be considered suspect. The dwarf des abeilles naines du sud-est de la Thaï- honey bees represent great potential for lande et de l’ile de Palaouan (Philippines). comparative studies in honey bee biology La petite abeille naine, Apis andreniformis and, indeed, have already provided some Smith (1858), a été récemment confirmée interesting insight into the evolutionary comme étant une véritable espèce biolo- gique (Wongsiri et al, 1990). Bien que cette a moins de pigment noir, ce qui est publication, ainsi que d’autres (Wu et Kuang, conforme à l’impression générale qu’A florea 1986, 1987; Rinderer et al, 1993a), le est principalement une abeille jaune alors démontrent clairement, ces travaux