Hymenoptera, Apoidea)

>lhetian JMfuseum ox4tates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK 24, N.Y. NUMBER 2 2 24 AUGUST I7, I 965 The Biology and Immature Stages of Melitturga clavicornis (Latreille) and of Sphecodes albilabris (Kirby) and the Recognition of the Oxaeidae at the Family Level (Hymenoptera, Apoidea) BYJEROME G. ROZEN, JR.' Michener (1944) divided the andrenid subfamily Panurginae into two tribes, the Panurgini and Melitturgini, with the latter containing the single Old World genus Melitturga. This genus was relegated to tribal status apparently on the grounds that the adults, unlike those of other panurgines, bear certain striking resemblances to the essentially Neo- tropical Oxaeinae of the same family. In 1951 Rozen showed that the male genitalia of Melitturga are unlike those of the Oxaeinae and are not only typical of those of the Panurginae in general but quite like those of the Camptopoeum-Panurgus-Panurginus-Epimethea complex within the subfamily. On the basis of this information, Michener (1954a) abandoned the idea that the genus Melitturga represents a distinct tribe of the Panur- ginae. Recently evidence in the form of the larva of Protoxaea gloriosa Fox (Rozen, 1965) suggested that the Oxaeinae were so unlike other Andreni- dae that they should be removed from the family unless some form inter- 1 Chairman and Associate Curator, Department of Entomology, the American Museum of Natural History. 2 AMERICAN MUSEUM NOVITATES NO. 2224 mediate between the two subfamilies is found. In spite of the structure of the male genitalia, Melitturga is the only known possible intermediary. Consequently it was of considerable interest to investigate the biology and larva of Melitturga clavicornis (Latreille) to see if data could be un- covered that would elucidate the interrelationships of Melitturga, the other Panurginae, and the Oxaeinae. The results ofthis study are divided below into three parts. The first records the observations on the ethology and nesting activities of Melitturga clavicornis. The second provides taxonomic descriptions of the immature stages ofM. clavicornis and its halictid cleptoparasite, Sphecodes albilabris (Kirby) [= fuscipennis (Germar)].1 In the light of the first two parts, the third discusses the relationship of Melitturga with the other Panurginae and the Oxaeinae and re-evaluates the taxonomic status of the Oxaeinae. This investigation was made possible because ofthe generous assistance and warm hospitality of Prof. J. de Beaumont, Lausanne, Switzerland, who not only led me to the nesting site of this species but joined me for several days in the field, when the observations for this paper were car- ried out. BIOLOGY OF MELITTURGA CLA VICORNIS (LATREILLE) The biology of this species has been treated by a number of workers in the past: Mocsary (1884), Friese (1891, 1922-1923), Malyshev (1925, 1935), and Bischoff (1952). Only the studies of Friese (1922-1923) and Malyshev (1925) attempt to be complete, and the latter alone stands as a reasonably well-rounded, accurate account. Ferton's (1920) informa- tive paper presumably reports on M. clavicornis in Africa, but the species identification is questionable, as clavicornis may not occur there. The following description is given, both because new information is included which will be important for a comparison ofMelitturga with other panurgines at a later date and because certain discrepancies between Maly- shev's and Friese's works can be clarified. DESCRIPTION OF HABITAT: The nesting site (fig. 1) of this species has been known to de Beaumont since 1930. It is on the nearly horizontal field of a public campground in the Rhone River valley just east of the small town of Sierre in the canton of Valais in Switzerland. The site is exposed to the sun for almost all of the day, and the small trees border- 1 The adults ofthis large-sized species were identified by comparison with named specimens kindly lent by Prof. J. van der Vecht, Rijksmuseum van Natuurlijke Historie, Leiden, the Netherlands. 1965 ROZEN: MELITTURGA 3 FIGS. 1-3. Melitturga clavicornis (Latreille). 1. Nesting area near Sierre, Switzer- land. Burrows were found over most of the field. 2. Several burrows before excava- tion. 3. Partly excavated burrow penetrating the column of a filled scarab tunnel. ing the field do not shadow the area. The field, which is well drained and approximately 200 feet square, is so sparsely covered with low grasses and clover several inches high that barren ground separates the clumps of plants. Although the soil is hard and compact on the surface, it is easily excavated, fine, and contains few stones. Numerous other Hymenoptera were encountered nesting in the field, the most common one being the bee wolf, Philanthus triangulum (Fabricius) (Sphecidae). The following observations were made onJuly 3 and 5, 1964. 4 AMERICAN MUSEUM NOVITATES NO. 2224 MATING BEHAVIOR: Although no actual copulations were noticed, the behavior reported here is obviously associated with mating. On the first day, which was warm and clear, males were first seen around 9 A.M., were common by 10:30, and then had decreased in abundance by 4:00 P.M., with one or two visible on the field by 4:45. During the heat of the day numerous males could be seen hovering slowly at nearly ground level to 15 feet or more in the air. Their slow flight was suggestive ofthat of a syrphid fly. Suddenly a male darted extremely rapidly up, down, or horizontally, apparently toward a female. Occasionally a group ofmales (up to seven or eight individuals) converged and rapidly pursued a female. Often one or more males followed a female loaded with pollen as she approached her nest. In an apparent attempt to avoid an encoun- ter, she dashed off and then in a short time returned to the area after she had presumably outdistanced her entourage. Premating behavior high in the air has not been observed in other panurgine bees. Because no individuals in copulo were seen, we can probably assume that copulation is brief. NESTING ACTIVITY: Burrow openings were found scattered over a wide area of the field and were situated either in the barren stretches between the clumps of low vegetation (fig. 2), at the edges of the clumps, or actu- ally in such clumps. Ordinarily there is but a single female to a nest, though one nest with two main tunnels that met near the surface had a female in each branch.1 Always open, the entrances of active burrows are usually without tumuli (fig. 2) though occasionally a tumulus was found either on one side of an opening or surrounding it. Malyshev (1925) always found the entrances without tumuli. The main burrow descends in a somewhat meandering fashion, in contrast to the drawings and description by Friese (1922-1923). Circular in cross section and with a diameter of from 7 to 8 mm. (in close agree- ment with the figures given by Malyshev, 1925), the main tunnel is without a built-in hard wall, and I saw no indication that saliva had been applied to it, as reported by Friese. Often, though apparently not always, the soil surrounding the tunnel is soft though otherwise of the same appearance and texture as the surrounding substrate. It is suffi- ciently consolidated that the surrounding earth can be chipped away, leaving it intact as a cylindrical column (fig. 3), perhaps 12 to 18 mm. in diameter. The column is penetrated either in the center or on the side by 1 Dr. William P. Stephen (in litt.), who studied the same nest site shortly after my visit, con- cluded that "most of these nests [nine examined] had a distinctly branched main burrow with the females each occupying one half." 1965 ROZEN: MELITTURGA the descending burrow and is apparently the filled exit burrow of a scarab, for several cast larval skins of the beetle were taken at the bot- toms of the columns. Whether the Melitturga fills in the old tunnel or merely avails itself of the softer soil of the already filled tunnel was not determined. Malyshev (1925) apparently found somewhat the same phenomenon, though he interpreted it differently. He stated that the walls of the main burrow (but not of the side tunnels) were always covered with a thin layer of sand. "This seems to indicate that the bee does not throw out the rubbish, but even takes the necessary material from the surface near the opening. The soil here [Gotnya, Russia] is coarse-grained, black TABLE 1 DIMENSIONS OF POLLEN MASSES AND CELLS OF Melitturga clavicornis (LATREILLE) Number of Average Range Samples Cell length 8 17.0 mm.a 15.0-18.0 mm.a Cell diameter 9 10.0 mm.a 9.0-10.0 mm.a Cell depth 10 10.5 cm.b 7.0-16.0 cm.b Shortest diameter of pollen mass 3 5.5 mm.a 5.0- 6.0 mm.a Longest diameter of pollen mass 3 7.5 mm.a 6.5- 8.5 mm.a a To the nearest half millimeter. b To the nearest half centimeter. earth covered with a thin layer of sand." This passage suggests that the "thin layer of sand" may be the same as the soft fill of the scarab burrow. It further suggests that the fill comes from the surface and not from the excavations of the side tunnel. A full understanding of this situation should develop as soon as observations are made when nest construction first begins. The bee burrow is usually open, though one was found late in the afternoon with a septum of soil below which was the female. On the morning of the second day, which was cloudy and cool, burrows were occasionally encountered that were filled with very soft soil below the open entrances.

Load more