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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STEM Pipeline is Gushing Women

Many of you have probably heard of the STEM pipeline dripping – that is, the idea that we’re losing lots and lots of students at each step of the educational process. Perhaps the step that is most relevant to me as someone who wants to go on to be a professor: only about half of those students who enter college in a STEM major will graduate with a STEM degree. This is already a sad pronouncement – we are losing so many of our students to things like poor class and assessment design, a lack of awareness of mental health issues, and a dearth of research opportunity to keep people engaged. These are all problems that, as a student of the PROFESS program at Drexel, I aim to learn about fixing.

Me, a young woman scientist, STEMMING it my senior year in undergrad.

But to actually have an impact, I will need to become a professor – and the STEM pipeline prognosis for women, and for minorities, is sadly far worse than that for overall scientists. According to a UC Berkeley study on chemists, women make up roughly 50% of college graduates in the field – but only 37% of PhDs, 22% of associate professors, and a measly 12% of tenured professors. There are many things that explain this ‘drip’ of women from the field (feels more like a gush than a drip, honestly) – they include everyday sexism from the ‘good old boys club’ of science that goes all the way to the top, wanting to earn higher salaries outside of academia, or needing time to start a family – which might not be compatible with the format of tenure-track jobs.

What I think this study, and others like it, show is that we’ve done a good job with outreach to girls to get them interested in science – despite the fact that female scientists are historically forgotten about in favor of their male counterparts (*cough* Rosalind Franklin *cough*) in our culture and the classroom, and despite the fact that science is more actively marketed to boys, we still see about 50% of our undergrads are women in several (though not all) STEM fields. Certainly, more outreach to young girls would not hurt, particularly in fields like IT, Engineering, and Physics where women are still under-represented even in bachelors programs. But this quote really resonated with me, about what the actual problem is here:

“You can tell a girl she’s smart her whole life, encourage her in school, buy her a chemistry set, send her to math camp, help her apply for college scholarships in STEM fields, and she’s still eventually going to walk into a classroom, a lab, or a job interview and have some man dismiss her existence, deny her funding, pass her over for a promotion, or take credit for her work. How about you work on getting those [people] out of power and quit telling me not to call girls pretty” – kelsium

And this idea, that men in science are actively not supporting women in science, has some pretty significant data behind it. An article in PNAS showed that elite labs run by men (and regular labs run by men) were significantly less likely to hire/train women PhD and postdocs than those run by women. In contrast, elite labs run by women were more likely to hire women than men – but by a less significant margin; and non-elite labs run by women showed no bias, unlike non-elite labs run by men. This problem is multiplied by the fact that there are more Academy/elite male scientists than females (in Chemistry, females make up only 6% of the National Academy of the Sciences chemists) – which means that in 94% of elite labs there’s an anti-woman bias.

The study in PNAS does indicate that they don’t know how many women applied to work in these labs – though they cite high rates of sexual harassment and negative attitudes towards maternity as reasons why many women may steer clear of male-dominated labs. The bottom line is that women in STEM are not being treated fairly or given access to equal opportunities – not really surprising, given how recently women were even allowed to start having careers at all.

Undeniably, women have made incredible strides in the last sixty to eighty years – at least at the undergraduate level. But the anti-woman bias held by the ‘good old boys club’ that has been the norm for the past 600 years of science needs to change and effort needs to go into enacting policies that work from the top down. Policies that support women in cases of sexual harassment, hiring bias, and family planning. Until these policies are enacted, no matter how many chemistry sets we give our young girls, we will not see a change in the gushing STEM pipeline for women.

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Breaking News: YOU Are the Scientist

Honeybee in Rochester
One of my favorite personal ‘sightings’ in Rochester!

This week I have discovered something so cool I can hardly contain myself, and so I must share it with all the other scientists I know and that includes YOU. You, yes. Every one of you reading this can go out into your backyard and take part in an awesome experiment as part of i See Change.

i See Change is a really cool project (partially in collaboration with NASA) that allows you to participate in investigating the impact of climate change in your area. There’s the online website and also an app version, for those of you more phone-friendly people. Their mission statement reads:

“iSeeChange is empowering communities to observe how weather and climate affect their environment. We strive to connect the public with national media & scientists to understand how climate change is impacting their daily lives.”

You can track climate and weather data using their journaling feature; you can add pictures of ‘extreme weather events’ in your area like tornadoes, hurricanes, and more (my suggestion – get inside!). They’ve just introduced a really cool “Investigations” feature where you can be a part of a more directed project, instead of simply uploading climate data endlessly into the ether.

Investigations seem to be about establishing baseline data across the country that will help the i See Change partners (researchers) to gather more data and faster and then understand larger trends. These ‘sightings’ (the information you upload) can help local communities become more involved in environmental decisions for their area – and more aware of their specific, local needs! Here are some examples of investigations:

  • Agriculture – How’s your crop doing? Share your growing season, and what’s changing.
  • Landlife: Birds, Bugs, and Other Critters – Make sightings of the animals you see each season. What’s different?
  • Smog and Air Pollution – Is it hazy? Hard to breathe? Tell us about air quality (and when you close your windows).
  • Coastal Erosion and Sea Level Rise – Shorelines are changing. Show us what’s different. Is the high water mark higher?
  • Landscapes, Fields, Backyards – Return to a stream, lake, river, forest, field, or backyard to take pictures throughout the year.

Not only does this seem to be an excellent way to help researchers collect data and get people involved in the science of climate change in their local area (as opposed to trying to conceptualize the whole globe!) but it strikes me as a really great educational tool. What better way to further scientific interest in kids than to show them they’re making valuable contributions to an ‘investigation’ by photographing and discussing with you all the changes in your backyard stream? You can help them make hypotheses, even test them, etc. all with an easy-to-use and free app. I’m always a fan of tools that make science and the scientific process accessible to a larger community – i See Change seems to do just that!

What do you think of the i See Change idea? Would you consider using the app – what investigation would you be most interested in following? Let me know in the comments!

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