Bee Bytes: Centris pallida

female Centris pallida
Female Centris pallida


Deserts. Common. Diggers.


Map made with Discoverlife


Name: ‘The Pallid Bee’ or ‘The Digger Bee’ (no official common name)

Family: Apidae (with: carpenter, honey, bumble bees)

States: Arizona, California, New Mexico, Nevada

male C. pallida digging; CC by SA 3.0 link through photo

Centris pallida are known for their vibrant, yellow-green eyes and pale fuzz as they buzz around desert palo verde – females are also known for the lovable ‘chaps’ on their rear legs which help them gather pollen.

C. pallida are some of the best bees at maintaining a stable body temperature; they are often found within 2 degrees Celsius of lethal overheating!

C. pallida females dig long tunnels to lay a single egg in a wax-lined cell, 8-10 cm under the dirt. These cells are provisioned with a soupy, orange-colored bread made of pollen and nectar. After sealing the cell, the mother fills in the whole tunnel with dirt and starts over for her next egg. Females often aggregate in the same area, collectively laying hundred of eggs in a relatively small area.

In early spring, the next generation of adults emerge and aggregate by the thousands to mate. Males emerge first, and begin searching the ground for females. Large males can smell females underground as they start to dig themselves out of their cells and will fight with one another to help dig her out and mate with her. Small males can’t afford to brawl so they employ a sneakier strategy! Hovering on the outside of the aggregation, they wait for escaped females to mate with instead.

Sources and Further Reading:

A friendly webpage written by C. pallida expert, John Alcock that summarizes his papers listed below.

Alcock J, Jones E, Buchmann S (1976). The Nesting Behavior of Three Species of Centris Bees (Hymenoptera: Anthrophoridae). Journal of the Kansas Entomological Society, 49: 469-474.

Alcock J, Jones E, Buchmann S (1976). Location before emergence of the female bee, Centris pallida, by its male (Hymenoptera: Anthrophoridae). Journal of Zoology, 179: 189-99.

Alcock J, Buchmann S (1985). The significance of post-insemination display by male Centris pallida (Hymenoptera: Anthophoridae). Z. Tierpsychol., 68: 231-43.

Alcock J (1976). The social organization of male populations of Centris pallida (Hymenoptera, Anthophoridae). Psyche, 83: 121-31.

Alcock J, Jones C, Buchmann S (1977). Male mating strategies in the bee Centris pallida Fox (Anthophoridae: Hymenoptera). The American Naturalist, 111: 145-55.

Chappell M (1984). Temperature regulation and energetics of the solitary bee Centris pallida during Foraging and intermale mate competition. Physiological Zoology, 57: 215-25.

Gilliam M, Buchmann S, Lorenz B (1984). Microbial flora of the larval provisions of the solitary bees, Centris pallida and Anthophora sp. Apidologie, 15: 1-10.

Roberts S, Harrison J, Hadley N (1998). Mechanisms of thermal balance in flying Centris pallida (Hymenoptera: Anthophoridae). Journal of Experimental Biology, 201: 2321-31.

Roberts S (2005). Effects of flight behavior on body temperature and kinematics during inter-mate male competition in the solitary desert bee Centris pallida. Physiological Entomology, 30: 151-7.

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Bee Bytes: Do All Bees Sting?

BeeByteLogoMany people are afraid of bees (and wasps) because of their stingers – but not all of our buzzing buddies actually sting. Which bees aren’t so sharp?

Gasteruptiid Wasp by zosterops (CC BY-NC 2.0; link through photo)
‘Gasteruptiid Wasp’ by zosterops (CC BY-NC 2.0; link through photo); the long, thin line at the end is the ovipositor.

1. Male bees (of any species) – A stinger is a modified version of the egg-laying part of a female bee’s body, called the ovipositor. Since males were never meant to lay eggs, they never evolved a stinger.

Despite not being able to sting, many male bees will buzz loudly and curl the end of their abdomen towards anything that grabs them. This mimics a female’s stinging position and the behavior is scary enough that even experienced bee handlers will often reflexively let go!

2. Stingless bees – The meloponines, or stingless honey bees, are a group of approximately 500 species that live in tropical and subtropical zones. Stingless is a bit inaccurate – female bees have stingers, but they are so tiny they cannot pierce human skin.

The 's' points to the incredibly tiny stinger of a meliponine bee. The lips on either side with the hairs are the ends of the abdomen. Michener [2000]
The ‘s’ points to the incredibly tiny stinger of a meliponine bee. The lips on either side with the hairs are the ends of the abdomen. Michener [2000]

Fairy bees (Perdita), and other mining bees (Andrenidae; ~3000 species), lack the part of the stinger that pumps venom, rendering them effectively stingless. Not to be outdone, the Dioxyini, a group of cuckoo bees that lay their eggs in the nests of other bees, have the most reduced stingers of all!

3. Most bees, most of the time – While male bees and bees with reduced stingers may be incapable of stinging you, bees only use their stinger if they are in danger. If you see bees (or wasps), leave the fear behind – move slow and watch your step, and you’ll leave sting-free.

Source for further reading: Michener CD. 2000. The bees of the world. Baltimore: John Hopkins University Press.

*This post modified and condensed from one written for Buzz, Hoot, Roar in 2017- check out their short, informational posts on all kinds of natural life here.


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Bee Bytes: Do Bees Actually Drink Sweat?

BeeByteLogo This past summer, you and I probably shared a similar bee experience: outside on a hot day, little metallic bees stuck to your bare arm, lapping up sweat from your skin.

These bees, called sweat bees, are from the Halictidae family and are very common. Between the US and Canada, there are approximately 520 known species of these shiny, and often colorful (like this Agapostemon texanus), insects. But why do they drink sweat?

Halictus ligatus, public domain photo by Insects Unlocked and Alexis Roberts
Halictus ligatus, public domain photo by Insects Unlocked and Alexis Roberts

Salt is necessary for egg production in insects (a female butterfly can lose more than 50% of the salt she’s born with in just one egg complement) and human sweat is absolutely loaded with it. Many insects have a hard time meeting their salt requirements, since nectar and pollen are not high in salts. This leads insects to drink our sweat, or even tears (a behavior exhibited by some bees from the Apidae family, though they may be after proteins too). Bees, moths, and butterflies will alight on the eyes of crocodiles and drink from mud puddles, feces, and urine to meet their salt needs.

In butterflies, this ‘puddling’ behavior (named for the plethora of butterflies found at mud puddles) is mostly seen in males, who transfer huge amounts of salt to females in their sperm. However female bees are commonly found drinking human sweat (which is why you may have experienced an unpleasant pinch when you try to brush one off your skin). This behavior is not believed to be harmful, so next time you see a sweat bee tell her: ‘Drink up!’

Augochloropsis metallica, public domain photo by Insects Unlocked and Lexi Roberts
female Augochloropsis metallica, public domain photo by Insects Unlocked and Lexi Roberts

Sources and Further Reading:

Adler P, Pearson D (1982). Why do male butterflies visit mud puddles? Canadian Journal of Zoology, 60: 322-5.

Banziger H, Boongird S, Sukumalanand P, Banziger S (2009). Bees (Hymenoptera: Apidae) That Drink Human TearsJournal of the Kansas Entomological Society, 82: 135-50.

Barrows, E (1974). Aggregation Behavior and Response to Sodium Chloride in Females of a Solitary Bee, Augochlora pura (Hymenoptera: Halictidae). The Florida Entomologist, 57: 189-93.

Dangles O, Casas J (2012). The bee and the turtle: a fable from Yasuni National ParkFrontiers in Ecology and the Environment, 10466-7.

Pivnick K, McNeil J (1987). Puddling in butterflies: sodium affects reproductive success in Thymelicus lineola. Physiological Entomology, 12: 461-72.

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Bee Bytes: Agapostemon texanus

Male Agapostemon texanus
Male Agapostemon texanus


Generalist. Widespread. Solitary.


Map made via Discoverlife
Map made via Discoverlife



Name: ‘The Green Sweat Bee’ (there are several)

Family: Halicitinae (with: other sweat bees, alkali bees)

States: Most likely all except Hawaii and Alaska


Agapostemon texanus belongs to one of North America’s most striking genera – all Agapostemon males and females have beautiful, metallic blue/green coloration. Males and females of Agapostemon species look very different (a phenomena called sexual dimorphism). Male abdomens are yellow-and-black/brown striped while female abdomens are consistently metallic and blue-green.

Abdomen of female Agapostemon texanus (public domain image, Lexi Roberts as part of ‘Insects Unlocked’)
Abdomen of female Agapostemon texanus (public domain image, Lexi Roberts as part of ‘Insects Unlocked’)

Of all the AgapostemonA. texanus is the most widespread, appearing from Costa Rica to Southern Canada. In the US, it is most common west of the Mississippi River. A. texanus has two generations a year, with mostly males active in the early fall and mostly females hibernating through the winter and active in spring and early summer (this split is due to a unique system called haplodiploidy).

Female A. texanus are strictly solitary, though females of closely-related species (like A. radiatus) have been found to make all their nests together in one area (called an aggregation) or potentially even use singular nests communally (A. nastus).

Agapostemon texanus (public domain image, Alejandro Santillana as part of ‘Insects Unlocked’)
male Agapostemon texanus (public domain image, Alejandro Santillana as part of ‘Insects Unlocked’)

A. texanus nest in the soil, creating long tunnels by digging. Females search for dark spots under pebbles or leaves to construct the entrance to the nests, making nests hard to spot by parasites. Females leave their nest open during the day as they forage on a variety of flowers (A. texanus are generalists) before closing the nest entrance in the late afternoon/early evening by pushing soil up from inside the main tunnel to close the door for the night. High security area!

Nests tunnels have been found up to 150 cms deep (nearly five feet!).

Sources and Further Reading (first is freely available and has a great drawing of an A. texanus nest!):

Roberts, R (1973). Bees of Northwestern America: Agapostemon (Hymenoptera: Halictidae). Technical Bulletin of the Agricultural Experiment Station at Oregon State University, 125: 1-23.

Eickwort, G (1981). Aspects of the Nesting Biology of Five Nearctic Species of Agapostemon (Hymenoptera: Halictidae). Journal of the Kansas Entomological Society, 54: 337-51.

Porter, C (1983). Ecological Notes on Lower Rio Grande Valley Augochloropsis and Agapostemon (Hymenoptera: Halictidae). The Florida Entomologist, 66: 344-53.

Waddington, K (1979). Flight patterns of Three Species of Sweat Bees (Halictidae) Foraging at Convolvulus arvensis. Journal of the Kansas Entomological Society, 52: 751-8.

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Bee Bytes: Are All Bees Social?

BeeByteLogoThink quick: Bee!

For most of us, a highly social hive of buzzing honey bees come to mind. But this is actually only a tiny sliver of the social structural pie. Here are some (but not all) other types of organization:

Solitary: Most bees are solitary, where a single female makes her nest alone. Solitary bees lay their eggs in small cells on top of a bed of food – the egg later hatches and feeds itself. Adults typically emerge from their cells around the same time, forage, lay their eggs, and then die while larvae/pupae wait underground for the next appropriate ’emergence’ season. This means adult generations do not overlap.

Gregarious nesters: These bees often appear social, as many solitary females will nest individually, but nearby one another, in ‘aggregations’.

Communal nesters: This is when multiple solitary females all share one nest, but lay their own eggs in individual cells within that nest.

Facultatively social: These species can be solitary or social, depending on environmental cues. In one species, Ceratina australensis, two sisters will sometimes form a colony together instead of nesting alone, with one foraging and reproducing and the other acting solely as a guard.

Primitively eusocial: Here, there are reproducing ‘queens’ and nonreproducing (but not sterile) ‘workers’. Queens and workers generally look similar, and workers can sometimes replace queens.

Photo credit: Meghan Barrett Apis mellifera, the Honey Bee
Photo credit: Meghan Barrett
Apis mellifera, the Honey Bee

Advanced eusocial: The honey bee colony: reproducing queens, nonreproducing, functionally sterile workers. Workers and queens do not look similar. The workers care for the queen’s young, and there are overlapping generations of adults.

Additional sources:

Wikipedia has a great chart (bottom of page) showing the differences between terms used to describe sociality, including: Eusocial, Semisocial, Subsocial,and Quasisocial.

This paper discusses some theory on the evolution of eusociality.

This paper addresses how advanced eusociality may have arisen through other types of sociality.

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Bee Bytes: Can you #WildID a Bee?

BeeByteLogoOn Twitter, nature-lovers will send scientists photos of an animal asking for a #WildID – or species identification. But can you #WildID a bee?

The answer: sometimes yes (but usually no).


Often bees of the same genera will look very similar (for example these two different species of male Agapostemon):

Agapostemon splendens (public domain image, Lexi Roberts as part of 'Insects Unlocked')
Agapostemon splendens (public domain image, Lexi Roberts as part of ‘Insects Unlocked’)
Agapostemon angelicus (public domain image, Lexi Roberts as part of 'Insects Unlocked')
Agapostemon angelicus (public domain image, Lexi Roberts as part of Insects Unlocked’)








And sometimes, two bees of the same species will look very different (like the abdominal coloration of these two female Augochloropsis metallica):

Augochloropsis metallica (public domain image, Lexi Roberts as part of 'Insects Unlocked')
Augochloropsis metallica (public domain image, Lexi Roberts as part of ‘Insects Unlocked’)
Augochloropsis metallica (public domain image, Lexi Roberts as part of 'Insects Unlocked')
Augochloropsis metallica (public domain image, Lexi Roberts as part of ‘Insects Unlocked’)








This makes telling a bee’s species from a photo very difficult; sometimes the features an entomologist must look at to ID a species are hidden under hairs, or even involve dissecting the bee.

However, sometimes a photo with location data can tell us everything we need to know to #WildID – some species have very distinctive features (especially when we know where the photo was taken, and thus what species are in that range). For example the triangle of black on the thorax of Bombus franklini (featured here), combined with information about the bee’s range, can be used to ID B. franklini with relative certainty. Sometimes even the time or flower a bee was spotted on can help #IDthatBee – if it is an early dawn forager, or a pollen-specialist that only visits a specific species.

Don’t be afraid to #WildID your next bee photo – even if the experts can’t get the species, often the next best thing (genera) can be ascertained with a glance. Check out Bees in Your Backyard to try your hand at IDing to genera, yourself!

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Bee Bytes: Bombus franklini



Endangered. Social. Narrow Range.


Map made via DiscoverLife; modified to most closely resemble Williams, Thorp, Richardson, and Colla (2014)
Map made via DiscoverLife; modified to most closely resemble Williams, Thorp, Richardson, and Colla (2014)Status: Critically Endangered, last recorded by Robbin Thorp in 2006

Status: Critically Endangered, last recorded in 2006 by Dr. Robbin Thorp

Name: Franklin Bumble bee

Family: Apidae (with: honey bees, carpenter bees)

States: Oregon and California

B. franklini has experienced a sharp decline since 1998, and has not been spotted in the wild for over a decade, earning itself a spot on the critically endangered species list and a spot as the Bee Bytes mascot. It also has one of the most narrow distributions for a bumble bee in the world.

The yellow half of the thorax (closer to the head) with an inverse U shape in black can be used to differentiate it from the similar looking B. occidentalis. 

Photo credited to Dr. Robbin Thorp
Photo credited to Dr. Robbin Thorp

Like other bumble bees, B. franklini are social; they live in colonies with a queen, who reproduces, and her daughters, who gather nectar and pollen. The colony does not overwinter.

B. franklini are generalists, meaning they can use a variety of flowers for food; like all bumble bees, they are buzz pollinators, vibrating at a high frequency to dislodge pollen from the flowers’ anthers.

A potential cause of B. franklini decline is the fungal pathogen Nosema bombi, which has been found with increasing prevalence on museum specimen from declining populations. It is possible exotic strains were introduced from Europe, due to the American agricultural industry’s use of bumble bees reared in Europe to pollinate crops.

These bees are ground-nesters, thought to live in abandoned rodent burrows in grassy meadows. A paucity of research on B. franklini means little is known about the species, making conservation efforts more difficult.

More resources on the species and its decline:

NPR: The Bumblebee Hunter

ICUN Redlist Entry

Test of the invasive pathogen hypothesis of bumble bee decline in North America

Evidence for decline in eastern North American bumblebees (Hymenoptera: Apidae), with special focus on Bombus affinis Cresson

Bumblebees of North America: An Identification Guide by Paul Williams, Robbin Thorp, Leif Richardson, Sheila Colla (2014; Princeton University Press).


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Introducing “Bee Bytes”!

Welcome to Bee Bytes, a #scicomm project to introduce bees to the public!

What is Bee Bytes?

Bee Bytes will be a weekly to biweekly series on my blog, where I write “bite-sized” posts about an invasive or native bee species in the United States, describing its distribution, taxonomic relationship, and a few fun facts in brief! Each post will be 256 words or less – the number of unique characters you can represent with just one ‘byte’ (and exactly as long as this post). The end will have extra resources, in case you want to look for more about your favorite bees.

I don’t get it, why bytes?

A byte is used to encode a single text-character in a computer; my ‘bee bytes’ will be used to encode a single bee in your memory!

Where can I find these bytes?

For now, get your Bee Bytes fix here on my blog; in the future, I’m hoping to make a ‘trading card style’ website where you can search the deck for your favorite bees. That can be an after-quals project.

How long will you be doing Bee Bytes?

With 4000+ species in the United States, I can write for the next 77 years or so before I cover every species we’ve got! By that time, we’ll have so much new information I might even have to start over!

4000 species? Aren’t you byte-ing off more than you can chew?

Listen, bugger – you can buzz right off with that negativity.



Check out this link for the impetus behind ‘Bee Bytes’.

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