If we talk about bees, the first thing that comes to mind might be the picture of a well-structured colony of insects flying around a honeycomb made of perfectly constructed wax cells full of honey.

But the truth is that not all bees known nowadays live in hierarchical communities and make honey. Actually, most species of bees develop into a solitary life-form unlike the classical and well-known honey bees (which are so appreciated in beekeeping).

Through this article, I’ll try to sum up the different life-forms of bees in order to shed light on this issue.

INTRODUCTION

Bees are a large diverse group of insects in Hymenoptera order, which also includes wasps and ants. To date, there are up to 20,000 species of bees known worldwide, although there could be more unidentified species. They can be found in most habitats with flowering plants located in every continent of the world (except for the Antarctica).

Bees pick up pollen and nectar from flowers to feed themselves and their larvae. Thanks to this, they contribute on boosting the pollination of plants. Thus, these insects have an enormous ecological interest because they contribute to maintain and even to enhance flowering plant biodiversity on their habitats.

Specimen of Apis mellifera or honey bee (Picture by Leo Oses on Flickr)

However, even though the way they feed and the sources of food they share could be similar, there exist different life-forms among bees which are interesting to focus on.

BEE LIFE-FORMS

SOLITARY BEES (ALSO KNOWN AS “WILD BEES”)

Most species of bees worldwide, contrary to the common knowledge, develop into a solitary life-form: they born and grow alone, they mate once when groups of male and female bees meet each other and, finally, they die alone too. Some solitary bees live in groups, but they never cooperate with each other.

Female of solitary life-form bees build a nest without the help of other bees. Normally, this kind of nest is composed by one or more cells, which are usually separated by partition walls made of different materials (clay, chewed vegetal material, cut leaves…). Then, they provide these cells with pollen and nectar (the perfect food for larvae) and, finally, they lay their eggs inside each cell (normally one per cell). Contrary to hives, these nests are often difficult to find and to identify with naked eyes because of its discreetness.

Solitary bee nest. In this picture we can see the partition walls, pollen and eggs inside each cell (Picture from USDA).

The place where solitary bees build their nest is highly variable: underground, inside twisted leaves, inside empty snail shells or even inside pre-established cavities made by human or left behind by other animals.

These bees don’t make hives nor honey, so these are probably the main reasons because of what they are less popular than honey bees (Apis mellifera). Although solitary bees are the major contributors on pollination due to their abundance and diversity (some of them are even exclusive pollinators of a unique plant species, which reveals a close relation between both organisms), most of the studies related with bees are focused on honey bees, because of what studies and protection of these solitary life-forms still remain in the background.

There exists a large diversity of solitary bees with different morphology:

1) Specimen of Andrena sp. (Picture by kliton hysa on Flickr). 
2) Specimen of Xylocopa violacea or violet carpenter bee (Picture by Nora Caracci fotomie2009 on Flickr).
3) Specimen of Anthidium sp. (Picture by Rosa Gambóias on Flickr).

There are also parasite life-forms among solitary bees, that is, organisms that benefit at the expense of another organism, the host; as a result, the host is damaged in some way. Parasitic bees take advantage of other insects’ resources and even resources from other bees causing them some kind of damage. This is the case of Nomada sp. genus, whose species lay their eggs inside other bee nests (that is, their hosts), so when they hatch, parasite larvae will eat the host’s resources (usually pollen and nectar) leaving them without food. Scientists named this kind of parasitism as cleptoparasitism (literally, parasitism by theft) because parasitic larvae steal food resources from the host larvae.

Specimen of Nomada sp. (Picture by Domingo Roldan on Flickr)

PSEUDOSOCIAL BEES

From now on, we are going to stop talking about solitary bees and begin to introduce the pseudosocial life-forms, that is, bees that live in relatively organized and hierarchical groups which are less complex than truly social life-forms, also known as eusocial life-forms (which is the case of Apis mellifera).

Probably, the most famous example is the bumblebee (Bombus sp.). These bees live in colonies in which the queen or queens (also known as fertilized females) are the ones who survive through the winter. Thus, the rest of the colony dies due to cold. So is thanks to the queen (or queens) that the colony can arise again the next spring.

Specimen of Bombus terrestris or buff-tailed bumblebee(Picture by Le pot-ager "Je suis Charlie" on Flickr).

EUSOCIAL BEES

Finally, the most evolved bees known nowadays in terms of social structure complexity are eusocial bees or truly social bees. Scientist have identified only one case of eusocial bee: the honey bee or Apis mellifera.

Since the objective of this article was to refute the “all bees live in colonies, build hives and make honey” myth, I will not explain further than the fact these organisms form complex and hierarchical societies (this constitutes a strange phenomenon which has also been observed in thermites and ants) normally led by a single queen, build large hives formed of honeycombs made of wax, and make honey, a very energetic substance highly appreciated by humans.

Specimens of Apis mellifera on a honeycomb full of honey (Picture by Nicolas Vereecken on Flickr).

As we have been seeing, solitary bees play an important role in terms of pollination, because of what they must be more protected than they currently are. However, honeybees, and not solitary bees, still remain being on the spotlight of most scientists and a great part of society because of the direct resources they provide to humans.

REFERENCES

Notes taken during my college practices at CREAF (Centre de Recerca Ecològica i d’Aplicacions Forestals – Ecological Research and Forest Applications Centre). Environmental Biology degree, UAB (Universitat Autònoma de Barcelona).
O’toole, C. & Raw A. (1999) Bees of the world. Ed Blandford
Pfiffner L., Müller A. (2014) Wild bees and pollination. Research Institute of Organic Agriculture FiBL (Switzerland).
Solitary Bees (Hymenoptera). Royal Entomological Society: http://www.royensoc.co.uk/insect_info/what/solitary_bees.htm
Stevens, A. (2010) Predation, Herbivory, and Parasitism. Nature Education Knowledge 3(10):36

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