Forelegs Are Used to Spread Scent

yellow and brown bee on black background

Biological Strategy

Bees

Holly Kerstiens

Image: Sam Droege / Flickr / Public Domain - No restrictions

Attach Temporarily

Living systems must sometimes, temporarily, stay in one place, climb or otherwise move around, or hold things together. This entails attaching temporarily with the ability to release, which minimizes energy and material use. Some living systems repeatedly attach, detach, and reattach for an extended time, such as over their lifetimes. Despite being temporary, these attachments must withstand physical and other forces until they have achieved their purpose. Therefore, living systems have adapted attachment mechanisms optimized for the amount of time or number of times they must be used. An example is the gecko, which climbs walls by attaching its toes for less than a second. Other examples include insects that attach their eggs to a leaf until they hatch, and insects whose wings temporarily attach during flight but separate after landing.

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Cooperate Within the Same Species

A species is a group of organisms capable of breeding to produce fertile offspring. When individuals within a species undertake activities that benefit one another, that cooperation benefits not just the individuals, but also local and wider populations of that species. Collaborating in activities such as finding food, controlling parasites, and protecting from predators enhances overall survival. To cooperate, there must be enough benefit to an individual, and especially to a population, to justify any risk taken by individuals. Through cooperation, risk is distributed among individuals and the benefits to the community are greater than the sum of the benefits to individuals. An example is birds that gather in flocks, a cooperative activity more beneficial than acting alone. While some birds forage, others watch for predators. When one finds food, others also feed on it. Despite potential short-term competition for an individual that finds food, over the long-term, that same individual benefits when others find different food sources.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Male bees use their forelegs to send mating signals and spread their scent.

Differences in the forelegs of bees are often a secondary sexual characteristic that affects male bees and plays a role in their chances of finding a mate.

Forelegs can be used to cover the females eyes as they mate. The different shapes and sizes of the forelegs between species cause different shadows and patterns of light to shine through as he covers her eyes. These patterns signal to the female bee that she is mating with her own species.

Forelegs are also used to collect scent, whether the scent is excreted as a pheromone (such as can happen in Leaf-cutter bees) or collected from a series of flowers (such as in Orchid bees). This scent is then used as a signal to attract a mate and to assure her that they are the same species. When secreting pheromones, the scent can also be used to distinguish the relationship between the female and her mate, to assure that they are not closely related. The forelegs can also come equipped with dense, soft hair to massage the sent into her antennae.

The forelegs can also be modified to collect oil from flowers in addition to pollen, though this is not a male-specific trait. The oils are collected using a dense brush of hairs on the front of the leg.

This information is also available from the University of Calgary Invertebrate collection, where it was curated as part of a study on design inspired by bees.

Image: Rob Alexander / CC BY NC - Creative Commons Attribution + Noncommercial

Megachile rotundata, with small forelegs

Image: Sam Droege / Flickr / Public Domain - No restrictions

Another genus of bees whose range is restricted to Australia; five species are known, but three of them are only known from male specimens, the females remain unknown. Overall, a good example of a set of bees that have lived on the planet for hundreds of thousands of years, but yet we hardly even know what they look like, let alone how they fit into the pollination system of Australian plants. Even such first-world countries as Australia have a very long way to go to finish the fundamental tasks of documenting the bee species and their distributions. We are a hundred years behind the ornithologists and their study of birds.

Last Updated April 3, 2019

References

“The forelegs of male leaf-cutter bees reveal mysterious structures: one of the tarsi is extremely enlarged and has a scoop-like protuberance. While evaluating the video recordings Professor Wittmann and his team discovered that shortly before copulation the female’s feelers are placed in the curved blade of the scoop. In the examination by electron microscope they also discovered that the scoop blade is pockmarked with tiny holes, the outlets of scent glands. The curved scoop-like shape serves the male as a ‘hand spray’, with which he sprays the feelers of his partner (her nose) with his sexual scent. At the same time the male bee places his forelegs, which in part are translucent, over his partner’s eyes, thereby creating a species-specific pattern of light and shadow.” Wittmann, 2002

Web page

The Bees' Kamasutra - University of Bonn Press Release

University of Bonn. | Wittmann D.

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Reference

Journal article

Chemical niche differentiation among sympatric species of orchid bees

Ecological Society of America. | 31/03/2019 | Zimmermann, Y. , Ramírez, S. R. & Eltz, T.

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Reference

Book

The Bees of the World: Second Edition

Hopkins Fulfillment Service. | Michener CD.

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