Worker-caste Differences in Army Ant Brains: Soldier Specialization

In my most recent publication with Drs. Sean O’Donnell, Susan J Bulova, and Christoph von Beeren entitled ‘Brain investment under colony-level selection: soldier specialization in Eciton army ants (Formicidae: Dorylinae)’, we discuss the differences in the brains of task-specialized workers in multiple species of army ants. 

Worker army ants come in a variety of shapes and sizes that generally correspond to the task that worker performs (form meets function). In the case of the Eciton burchellii cupiens to the left (a), the grey arrow points to a small ‘foraging’ worker ant who cares for brood, assembles the nest, forages for food, and cares for queen and soldier ants. The white arrow points to a larger ‘soldier’ worker ant in charge of colony defense (the mouth parts are so large that this ant can’t even feed itself!). Neither of these belongs to the reproductive caste, like queens, yet they look very, very different and complete very different tasks too!

Different tasks impose cognitive loads on the different regions of the brain that help the organism complete them (for example, flight requires an organism to bring in a lot of visual information quickly so it imposes a large load on the visual processing region of the brain called the optic lobes). Since brain tissue is expensive to produce and maintain, evolutionarily-successful organisms will invest more in the parts of the brain that help them deal with the cognitive load of their behaviors (and will not invest in more brain tissue than strictly necessary, to conserve those resources for other tissues like reproductive organs or muscle).

At the colony level, there may be selection across different worker types so that workers, like soldiers, with reduced sets of behavior have smaller brains than other workers, like foragers. In b, above, we see a foraging worker (A) has a much larger brain relative to body size than the soldier (B) – and a similar size brain, even regardless of the differences in body size!

Looking across eight species of army ants, we assessed the volumes of the total brain, mushroom bodies (centers of learning, memory, and sensory integration), optic lobes (visual information processing) and antennal lobes (olfactory information processing) in forager and soldier workers. We found:

  1. As body size (measured by head capsule volume) increases, the ratio of brain:body increases sharply in support of Haller’s Rule (the idea that there is a minimum size the brain can be and still allow the organism to function as that type of organism). In Fig 2a to the right, we see that as body size gets very, very small, brains take up significantly more space in the head because we are approaching the minimum brain size it takes to function as an ant of any kind!
  2. Soldiers, despite being significantly larger (open symbols in 2b) do not have significantly larger brains than workers of the same species that have a smaller body size (closed symbols) and their ratio of brain size relative to their body size was significantly smaller. Soldiers – larger bodies but relatively smaller brains (Figure 1b illustrates this well).
  3. Not all regions of the brain are equally affected (Figure 3; not shown but can be found here) by this forager-soldier difference. The relative volumes of the mushroom bodies and antennal lobes compared to the rest of the brain volume was smaller in soldiers of all eight species (meaning they de-prioritize sending their already limited resources to these regions).

In total, these results suggest that there can be consistent, colony-level selection on the brains of workers in army ants and that specialized soldiers have reduced investment in their brains (particularly in the mushroom bodies and antennal lobes) to correspond with their reduced set of behaviors.

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The Third Quarter: Checking In

Me, in the field having a successful bee-catching day.

If I thought the second quarter of this year went fast, quarter three has gone even faster. I’m writing this a tad early – I’m currently (as of this post) in Cuba, so I had to write this post in advance since my internet access is spotty depending on my day’s activities.

The big thing I want to emphasize about this last quarter: I passed my candidacy! Indeed, I am now a PhD candidate – and coming off the back of a pretty successful field season, this feels especially good. I am excited to get the chance to settle down and work on my own thesis specimen this fall.

I met 3 of 4 goals (as expected!) for last quarter – Candidacy Boss Battle, Part 2; The Pallid Bee; and at least started Carpenter Contemplation (an ongoing meditation on America’s hardest-working bees). What’s on the docket for July-September?

  1. Carpenter Contemplation, part 2 – Returning to New York to see how my nest boxes are doing and potentially gather some genetic and cognitive data!
  2. Colliding Conferences – Conferences here, conferences there, oh my! I’m currently organizing two conferences – the Evolution in Philadelphia Conference and also, hopefully, the NE regions Social Insect conference.
  3. Termite Trials – To increase the sample size of one of our soon-to-be-papers, we need to run a few more termites through our histology mill. Sit tight…
  4. Pest Mess (please!) – This is the one I just can’t seem knock off my to-do list – third time’s the charm? Hopefully, the Tetramorium will be plentiful outside upon my return from Cuba and ripe for experimental tests!

I’ll admit that my to-do list has really gotten to be extensive – I am hoping after my field season is over I might have the chance to calm down a bit. Here’s to a happy, and productive, summer!

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The First Field Season

Me and a male Centris cockerelli friend; Tucson, AZ.

I arrived back from my first field season in Arizona on May 5th, and have been running around like mad ever since – trying to process specimen, taking my qualifying exam, and prepare for my next two field seasons this year (to New York, starting tonight, and Cuba, in June). But I felt I should take some time to reflect on the five biggest lessons I learned from this first foray into fieldwork.

  1. Me, in the Papaj lab, using Steve Buchmann’s net to collect bees from trees.

    Never underestimate the generosity of your peers – the number of people it took to make this season ‘go’ is astounding. From my ‘funders’ (fiance, Alex, and grant giver, B Cavello), to those that gave me lab space or let me borrow/taught me how to use equipment (literally a dozen people and counting), to those that let me stay with them (the amazing Kathryn Busby) which really made the trip affordable and fun, there are so many people who believed in me and supported me throughout this field season. The first big lesson I learned was to not be afraid to ask for help or support; the scientific community has a ton of wonderful people in it who want to help make science happen, and this field season I have countless people to thank for their generosity.

  2. Nothing will go according to plan – part of the reason it took so many people to make the season happen is because nothing went according to plan! The bees showed up 3 hours away from where I was staying, so suddenly new lab space and housing had to be found closer to where they were. Equipment suddenly became inaccessible, requiring me to find new people to borrow it from. At every turn, it felt like my carefully constructed plan (that I had made in January, because I am a planner at heart!) was breaking apart. And yet, somehow, thanks to all the people who came together to help me out, everything came back together again at the end of the season and I got to test out my equipment and collect a lot of specimen. I think being flexible is the key to field work – have plans for if you don’t get your equipment running the way you would like, or if your organism appears elsewhere than expected (or later than expected…).  Having a flexible mindset in how and where you gather data, and what data you gather, will help your season be more productive.

    On my cactus tour, avoiding the spines while practicing plant ID.
  3. Attitude is half the battle – Reader, when I did not find my bees for the first three weeks of the season I was DESPONDENT. But honestly, that’s just fieldwork for you and each day you need to get up and at ’em again. In the meantime, keep your eyes and ears peeled for other interesting phenomenon and do whatever you can to keep your spirits high; getting down on yourself will only make things even harder. Sometimes this may mean taking a break when things aren’t going well – a good taco, mountain view, cactus tour, fun reading day, etc, can do wonders to restore your spirit.
  4. Bring more vials – I ran out of vials about eight times in five weeks, it was incredible. I had no idea one could possibly use so many vials. How??? This isn’t just for vials, its for all supplies – bring more than you need. Things will break, get lost, evaporate if you don’t seal your EtOH container tightly enough (*sigh*) etc – having lots more than you thought you needed will help you survive these curve balls.
  5. No, these are not mini-pineapples. This is a cactus, with fruit.

    Fieldwork is fun! – There is nothing more enjoyable than being out in nature, intentionally observing things, day in and day out and getting to call it ‘work’. Particularly, being in an area that is so different from where I grew up and that has such great diversity was an amazing experience. Each day was a revelation, watching cacti grow flowers and bees emerge from the ground, seeing spiders and lizards catch prey, following flower-petal trails to seed-harvesting ant nests… it was all tremendously enjoyable, and I can’t wait to do it again.

Ant nest surrounded by palo verde flower petals.

I’d like to thank everyone on below for their help – accessing lab space or supplies, providing me with a couch or guest room to sleep on/in, teaching me how to use new equipment, checking different field sites for me, providing endless encouragement, and even financial support. I could not have done this without all of you believing in me, and with that belief supporting me in so many ways.

Thanks to my Drexel support: Dr. Sean O’Donnell, Katie Fiocca, Dr. Jacob Russell, Dr. Jennifer Stanford, and Dr. Michael O’Connor; to my lodging/funding support: Sarah Cook, Ellen and Adam Lowry, Kathryn Busby and Logan Schoolcraft, Alexander Glica, and B Cavello (Women’s Mini-Grant); to my University of Arizona support: Dr. Stephen Buchmann, Dr. Dan Papaj, Dr. Wulfila Gronenbergm Dr. Goggy Davidowitz, Dr. Judie Bronstein, Noah Giebink, and Bruce D Taubert; to my Arizona State University support: Dr. Jon Harrison, Dr. Kaitlyn Baudier, Dr. Jennifer Fewell, Dr. Rebecca Clark, and Megan Duwel.

And, always, a thank you to Anne Zimmer and Richard Barrett – for believing in me.

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Bee Bytes: Centris pallida

female Centris pallida
Female Centris pallida

 

Deserts. Common. Diggers.

 

Cpal
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_centris_pallida_digging
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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The Second Quarter: Checking In

Me with my trusty wasp brain! Brain section within this photo credit to the O'Donnell lab and Drexel University.
Me with my trusty wasp brain! Brain section within this photo credit to the O’Donnell lab and Drexel University.

Wow have the past few months flown by – year two of your PhD is no joke! First, I’d like to recognize all the big things I achieved in this last quarter (in no particular order):

  1. Went to ESA EB and presented on wasp brains
  2. Organized a field season to Arizona
  3. Presented a poster and helped my undergraduates make two posters for a conference
  4. Applied for four grants
  5. Finished the termite retina project
  6. Had my first committee meeting #CandidacyBossBattlePart1
  7. Embedded and sliced all the bee/spider brains #BrainDraincomplete
  8. Earned my graduate minor in Undergraduate STEM Education
  9. Was on a podcast! My very first #SuperwomeninScience
  10. Hosted Biotweeps – and had a ton of fun
  11. Brought two new undergraduates into the lab, trained them on the first project, and developed materials for a new mentorship training program that I am implementing

There is a lot to be proud of on this list.

What things didn’t I get to? Well, the blog took a huge backseat (my last Bee Byte is two months ago!) and I did not finish the Pest Mess (one of my big goals in my last goal-setting post) – mostly because all my ants died, before giving them the pesticide… oops.

So what are my goals for quarter two – April through June?

  1. Candidacy Boss Battle, Part 2: Sometime between April and June it’s time for my full-on committee meeting and any revisions to my proposal that may come from this. Bring on the #nerves.
  2. The Pallid Bee: A successful first field season out in Arizona would be a big boon to my thesis. Luckily, I have a great crowd supporting me at University of Arizona – and back home.
  3. Pest Mess (attempt 2?): Shall we try again? Hopefully, in May I’ll have some time to grab fresh Tetramorium and give these last few experiments one more whirl.
  4. Carpenter Contemplation: If Pest Mess doesn’t happen you can bet it will be because of the Carpenter bee project I have sitting in my back pocket, which will require some trips up to NY in May.

Hopefully, I’ll have some time to update this space with exciting news about grants, my field season, and other upcoming trips – as well as more Bee Bytes – ASAP. I’ll be celebrating my plane ride to Arizona with a Bee Byte on my thesis species, Centris pallida, so stay tuned for that – coming April 4!

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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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The First Quarter: New Years Goals

'Happy New Year! Bonne Annee Mes Amis!' by DaPuglet (CC BY-SA 2.0; link through photo).
‘Happy New Year! Bonne Annee Mes Amis!’ by DaPuglet (CC BY-SA 2.0; link through photo).

Happy New Year! May all of our 2018s be better than our 2017s.

I recently talked about goal-setting on Twitter, and how hard its been to follow through on many of my goals in my PhD program due to the ever-changing nature of the degree. The challenges and stresses are highly variable throughout the year, and I’ve come to the realization that annual goals – at least this coming year – probably won’t make much sense for me. Instead, I’ve decided to try out quarterly goals, with one big and two medium size professional goals to work on and evaluate every three months. For my first quarter (Jan 1 – March 31):

 

  1. Candidacy Boss Battle, Part 1: Plan my first field season and have my first committee meeting
  2. Brain Drain: Get through a round of bee and spider brain embedding
  3. Pest Mess: Run the last few ant trials to get started on that paper (this may extend into May/June)

Now, ‘Candidacy Boss Battle’ probably doesn’t seem like that big of a goal, but I want to give the process, and the emotional toll it’s likely to take on me, the respect it deserves. Here’s what I think that will likely entail:

  1. Reading about 1 paper a day
  2. Scheduling, organizing, attending the committee meeting
  3. Reminding myself to breathe for the 2 weeks prior to the committee meeting
  4. Making significant revisions to the proposal itself
  5. Organizing a field season in an area where I don’t know the facilities or tools
  6. Coming up with a back up idea for if I don’t find the aggregations
  7. Creating a presentation

So, given all the above, I feel like it’s a pretty big goal. Brain Drain is a pretty small goal in comparison, but would give me a cool graphic for my presentations and would keep pushing the spider brain project along as my undergraduates keep chipping away at the backlog. Pest Mess is more ambitious – mostly because it takes a long time to do the work (multiple weeks, uninterrupted), less that it is a lot of work to do. In any case, each of these would keep the lab humming along at a nice pace and my career progressing similarly.

I’ve also been thinking about personal goals for 2018 – 2017 was somewhat unhappy for me and I want to make 2018 better. I think some of this will be hard for me, and realistically won’t happen this year, because changing how you think and what you value is hard. But here are some of the things I’m going to at least try to be more aware of in 2018:

  1. Saying ‘no’ more often.  – I’ve spent a lot of time prioritizing making others happy, helping others, over helping myself. This is, in moderation, a character trait of which I am proud. It has led me to meet amazing people and have incredible, unique experiences. But I also become so busy and stressed that it strains my relationships with those I love, and my relationship with myself. It has given me incapacitating anxiety and led to depression. I need to learn to say ‘yes’ to me, and ‘no’ to others, more often.
  2. Valuing my mental and physical health. – We live in a world where pushing your body and mind beyond what is healthy is romanticized as an incredible devotion to your work. However this devotion hurts, when you take away the Instagram filters. This year, it is time to put my mental and physical health on the priority list – to stop joking about or in any way devaluing the importance of taking care of me.
  3. Bitter or Better. – “When something happens that you cannot control, you can choose to become bitter – or become better. Choose better.” – to paraphrase Sister Karlien from high school. This is something I used to be good at that I’m afraid the past two years have caused me to fall back from. I’ve got a lot of bitterness to let go of, to remember the positive feelings that make me happy. There’s a lot to be grateful for in my life, and even as times are complicated and tough, I need to remember ‘better’ is the way to go.
  4. Accepting my humanity. – Struggling with perfectionism, impostor syndrome, intense fears of failure, and self-imposed unrealistic expectations has only made the graduate school environment even more difficult. This year, I hope to accept my humanity – the process of failure as human, the importance of mistakes, letting go my harsh self-criticisms, seeing others that I admire in a more realistic light.

I hope that your 2018 is off to a good start – and that you use the beginning of the year to reflect on who you wish to become. I am hoping to find some time in future posts to discuss how, after you make a goal, to follow through using different types of step-organizing strategies that work for PhDs and life!

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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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