Alvaro Wille

Nesting biology of tropical solitary and social sweat bees,Lasioglossum (Dialictus) figueresi Wcislo andL. (D.) aeneiventre (Friese) (Hymenoptera: Halictidae)

SummaryThe nesting biology of a mainly solitary bee,Lasioglossum (Dialictus) figueresi, is compared with that of a possible relative and mainly eusocial bee,L. (D.) aeneiventre. These bees nest in the ground in highly disturbed areas in the Meseta Central of Costa Rica. Information is provided on social organization, male production, diel and seasonal activity patterns, pollen utilization, natural enemies and nest architecture. L. (D.) figueresi nests within aggregations in vertical earthen banks, and 80–90 % of females are solitary during the nest-provisioning phase. Social nests contain two (or rarely three) females which may be either equal or unequal in reproductive status (i.e. mated with developed ovaries or not). Solitary nests and two-female nests do not experience different rates of parasitism. Mid-way through the dry season, females cease provisioning at a time when otherL. (Dialictus) remain active. Females typically remain within their nests, although they occasionally forage for nectar. This behavior is similar of that of “spring gynes” of temperate eusocial species. The egg-to-adult developmental rate ofL. (D.) figueresi is unusually slow for halictine bees, however, so that all the adult females die before their brood eclose in April and May, precluding overlap of generations. The eclosed offspring remain in open cells within their natal nests until mid-June, when both males and females emerge to mate. These newly mated females either establish new nests or re-use old ones. L. (D.) aeneiventre nests within aggregations in horizontal ground or in vertical banks. A foundress female digs a nest at the beginning of the dry season, although some re-activate old nests. Foundress nests develop into colonies with various kinds of social organization. In contrast toL. (D.) figueresi, L. (D.) aeneiventre is active nearly all year round, except during periods of heavy rain, and produces up to three broods per year.Sweat bees (Hymenoptera: Halictinae) are a socially heterogeneous group of mainly ground-nesting bees which are abundant world-wide. Intra-specific variation in social behavior is prevalent both within and among populations, presumably indicating social and environmental control of behavioral modifications (see e.g. Sakagami and Munakata, 1972; Eickwort, 1986; Packer, 1990; Yanega, 1988; reviewed in Michener, 1990). The initial stages of hymenopteran social evolution are represented by solitary individuals and those in undifferentiated societies, yet their biology is not well known, as is true for the numerous tropical halictine species or populations (see Michener, 1990).The subgenusDialictus ofLasioglossum is a primarily New World group of several hundred species (Moure and Kurd, 1987). These bees are monotonously similar in structure and appearance, yet diverse in social behavior. FemaleLasioglossum (Dialictus) figueresi are usually solitary, and structurally are very similar to their social relativeL. (D.) aeneiventre (Wcislo, 1990 a). The systematic placement of these species with respect to otherL. (Dialictus) is uncertain, but they have no obvious affinities to other recognized species groups (G. C. Eickwort, pers. comm.). Unusual morphological features, such as large size, yellowish wings and pubescence, and features of the genital organs, may indicate thatL. (D.) figueresi is the more derived of the pair, and may therefore be secondarily solitary, as is known for other sweat bees (Packer, 1991).

A technique for collecting stingless bees under jungle conditions

SummaryMany stinglees bess seem to be restricted to the jungle, where they are difficult to collect by the usual methods. For this reason a very simple collecting technique was devised: Commercial (Apis) honey and water were mixed in proportions of 1∶1 and sprayed on leaves by means of a household hand sprayer. The technique was very successful, although the first time that the bait is used in an area, the bees may not arrive for an hour or more.ResumenCiertas abejas Melipónidas de las selvas tropicales son muy dificiles de colectar por los métodos corrientes. Este hecho indujo al autor a usar la siguiente técnica: una mezcla de miel de abeja comercial y agua, en la proporción de 1∶1, se rocía por medio de un atomizador sobre el follaje. Esto sirve como un atrayente, dando magníficos resultados, aunque la primera vez que se usa en una area, las abejas pueden tardar una hora o mas en llegar.ZusammenfassungViele stachellose Bienen scheinen nur im Dschungel vorzukommen, wo sie mit gewöhnlichen Methoden nur sehr schwer gesammelt werden können. Um dieser Schwierigkeit zu entgegnen wurde eine sehr einfache Anlocktechnik entwickelt. Im Handel erhältlicher(Apis-) Honig und Wasser wurden 1∶1 gemischt und mit einem gewöhnlichen Haushalt-Sprühgerät auf Blätter verteilt. Diese Methode erwies sich als sehr wirksam, obwohl sich die Bienen bei einer lokal erstmaligen Anwendung der Sprühtechnik nicht notwendigerweise vor Ablauf einer Stunde an der besprühten Stelle einfinden.