Handling sticky Resin by Stingless Bees: Adhesive Properties of Surface Structures

Abstract

Many Stingless Bees (Hymenoptera: Meliponini) like Tetragonisca angustula collect resin to defend their nests against intruders like ants or Robber Bees. Small portions of resin are attached to intruders bodies and extremities causing their immobilization. It has been observed that resin is removed easily from the bee's mandible but adheres strongly to the intruder's cuticle. We tested the hypothesis that resin sticks lesser to the mandibles of Stingless Bees than to the surface of intruders due to special surface structures or adhesive properties of these structures. The surface structures of the mandible of T. angustula and the trochanter of Camponotus sericeiventris were studied by scanning electron microscopy. To measure adhesion properties, selected surfaces were fixed on a fine glass pin and withdrawn from a glass tip covered with resin. The deformation of the glass pin indicates adhesion forces operating between the resin and the selective surface. The absolute value of the forces is computed from the glass pin´s stiffness. It has been shown that resin sticks more to the smooth mandible of the bee than to the structured trochanter of the ant. A new hypothesis to be tested says that the bees might lubricate their mandibles with nectar or honey to reduce the resin's adhesion temporarily.

Resin Use by Stingless Bees: A Review

“…Stingless bee body parts do not appear to possess inherently anti-adhesive properties. Gastauer et al [94] used electron microscopy and adhesive force experiments to compare the mandibles of stingless bee Tetragonisca angustula and the trochanter of invader ant Camponotus sericeiventris. They determined that resin actually adheres more to the smooth bee mandible than it does to the scaled ant trochanter.…”

Interaction between honeybee mandibles and propolis

“…Similar to honeybees, stingless bees harvest resin to build their nests and defend it against intruders [17]. Resin can easily be removed from the mandible surface without leaving residue behind [18,19]. It was therefore suggested that stingless bees might temporarily lubricate their mandibles to reduce resin adhesion [19].…”

“…Resin can easily be removed from the mandible surface without leaving residue behind [18,19]. It was therefore suggested that stingless bees might temporarily lubricate their mandibles to reduce resin adhesion [19]. In [20], it was observed that stingless bees were not able to handle propolis until they reached a certain age.…”

“…The anatomy of bee mandibles has previously been described [6][7][8]19], though not with a detailed focus on the medial surface of the mandible tip (see below in Figure 3B). However, this part is especially interesting in terms of propolis processing, since this surface is in intensive contact with the sticky material during biting and shaping it.…”

“…We found that there were several ridges and ledges on the medial surface of the mandible forming a channel between them. A hairless and sharp edge on one side could be used to cut materials as it has been suggested for the mandible of stingless bees [19]. Long flexible hairs grow on one edge and reach over half of the mandible.…”