Field Guide to the Common Bees of California

Including Bees of the Western United States

By Gretchen LeBuhn, Noel B. Pugh

UNIVERSITY OF CALIFORNIA PRESS

Copyright © 2013 The Regents of the University of California
All rights reserved.
ISBN: 978-0-520-27284-2

Contents

Preface, x,
AN INTRODUCTION TO BEES, 1,
What Are Bees?, 2,
Importance of Bees, 5,
Bee Diversity, 7,
Bee Morphology, 8,
Bee Life Cycles, 17,
Evolution of Social Behavior: Social versus Solitary Bees, 20,
Parasites and Robbers, 22,
Other Parasites and Predators, 23,
Nesting, 25,
Pollination Basics, 28,
Ecosystem Services and Bees, 36,
Conservation of Bees and Other Pollinators, 41,
Studying Bees, 44,
Identifying Bees, 50,
BEE FAMILY AND GENUS ACCOUNTS, 57,
Plasterer or Polyester Bees (Family Colletidae), 60,
Yellow-faced Bees or Masked Bees (Genus Hylaeus), 61,
Polyester Bees or Digger Bees (Genus Colletes), 63,
Sweat Bees (Family Halictidae), 66,
Sweat Bees (Genus Halictus), 66,
Green Sweat Bees (Genus Agapostemon), 70,
Sweat Bees (Genus Lasioglossum), 74,
Sweat Bees (Genus Dufourea), 76,
Cuckoo Bees (Genus Sphecodes), 78,
Mining Bees (Family Andrenidae), 82,
Digger Bees or Miner Bees (Genus Andrena), 82,
Panurgine Bees (Genus Panurginus), 85,
Miner Bees (Genus Perdita), 87,
Leaf-cutter Bees or Mason Bees (Family Megachilidae), 90,
Resin Bees or Mason Bees (Genus Dianthidium), 91,
Carder Bees (Genus Anthidium), 93,
Large Leaf-cutter Bees (Genus Megachile), 96,
Small Leaf-cutter Bees or Mason Bees (Genus Osmia), 100,
Leaf-cutter Bees (Genus Ashmeadiella), 105,
Mason Bees (Genus Hoplitis), 107,
Mason Bees (Genus Heriades), 109,
Cuckoo, Carpenter, Digger, Bumble, and Honey Bees (Family Apidae), 112,
Honey Bees (Genus Apis), 112,
Squash Bees (Genus Peponapis), 115,
Habropoda Bees (Genus Habropoda), 117,
Cuckoo Bees (Genus Nomada), 119,
Mining Bees (Genus Anthophora), 122,
Bumble Bees (Genus Bombus), 124,
Long-horned Bees or Sunflower Bees (Genus Diadasia), 133,
Long-horned Bees (Genus Melissodes), 135,
Large Carpenter Bees (Genus Xylocopa), 138,
Small Carpenter Bees (Genus Ceratina), 142,
Long-horned Bees (Genus Eucera), 145,
Long-horned Bees (Genus Tetraloniella), 147,
Cuckoo Bees (Genus Triepeolus), 149,
Appendix 1: Bee Families and Genera Found in California, 153,
Appendix 2: Key to Females of Genera Included in This Book, 155,
Glossary, 161,
Resources, 165,
Index, 167,

CHAPTER 1

AN INTRODUCTION TO BEES

What Are Bees?

Anyone who has spent a lovely warm morning in a garden in spring has shared company with a bee. From a farm in the Central Valley to a community garden in the center of Los Angeles, bees are busy buzzing around, visiting flowers, gathering resources for their offspring, and in the process, transferring pollen from flower to flower.

Bees are flying insects that first emerged about 100 million years ago, during the Cretaceous period, as part of the radiation of insects. The earliest record of bees is from fossilized amber in Myanmar (formerly Burma).

Bees are part of a larger group of insects, the order Hymenoptera that includes wasps, sawflies (a primitive and less well-known group), and ants. Bees belong to a large group within the Hymenoptera that are distinguished, in part, by having females with stingers. This group is called the Aculeata and contains the bees, ants, and stinging wasps. Recent work on the relationship between bees and wasps shows that bees are really just a very specialized group of wasps. Formally, we say that bees are in the superfamily Apoidea along with the sphecid wasps and make up the group Apiformes. No wonder bees and wasps can be so hard to tell apart!

While beetles were probably the first pollinators, bees were the first group of insects to really show a diversity of adaptations for pollination, such as specialized hairs and leg modifications, both for carrying pollen. This close relationship between bees and flowers is thought to have aided in the rapid evolution of different types of flowering plants and has strongly influenced both the body plans and lifestyles of bees and flowers.

When you look at most bees, you see a fairly hearty and hairy flying insect. Although there are bees that are slender and sleek, the most well-known, like the bumble bees and honey bees, are robust and hairy. Their hairs are an essential part of the service that bees are renowned for, transferring pollen from plant to plant. The hairs hold pollen onto the bee body. However, while it may seem bees are providing this service to plants free of charge—almost as if the flowers were taking advantage of them—the bees are actually getting great benefits from the interaction. What the bees are really doing is searching out food for their offspring and themselves. Bees rely on plant pollen for protein and nectar for energy. In fact, the sole source of protein for most bees is pollen. These bees could not exist without flowers to feed them.

When you see a bee visiting a flower, it is probably either collecting pollen or drinking nectar. If the bee is collecting pollen at flowers, she is a female gathering food to take back to her nest for her larvae. She might stop to fill up on some nectar, but her primary aim is to gather pollen for her offspring. This behavior highlights one big difference between bees and the closest wasp relatives of bees, the sphecoid wasps: the larvae of sphecoids are carnivorous, eating spiders and insects, whereas bee larvae are vegetarians, relying on pollen for protein. Of course, as with everything in nature, there is an exception to this rule: a group of tropical bees that feed their offspring carrion. If you see a bee simply drinking nectar, it is more likely to be a male bee. Male bees do visit flowers to tank up on nectar, but they do not collect pollen, as they do not provision nests.

At first glance, it can be difficult to tell bees, flies, and wasps apart because they have similar sizes and colors. Flies and wasps are confusing because they often look like bees. Some striped flies may actually be bee mimics, trying to fool predators! To tell bees and wasps from flies, there are three main distinguishing features: the number of wings that there are on each side, the shape of the antennae, and where the eyes are placed on the face. Let's start by distinguishing flies from bees. First, the number of wings on a side makes it easy to distinguish flies from bees and wasps. Flies have a single wing on each side. Bees and wasps have two per side.

It can be hard to tell that bees have a pair of wings on each side, because the wings on bees and wasps can be hooked together with special hooks called hamuli. When looking for bees on flowers, you can often tell that an insect is a fly because its wings are not neatly folded over its back; instead they point out at an angle. Second, you can look at the insect's antennae. Flies generally have short, thick antennae, whereas bees have longer, thinner antennae. Finally, bees have large eyes that are on the side of the head. Flies have large eyes on the front of the head. Other general rules of thumb are that bees tend to be hairy, and they carry loads of pollen, whereas flies have fewer hairs and do not generally carry pollen. This does not work when distinguishing male bees from flies, as male...