Deserts. Common. Diggers.

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

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.

Many 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?

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.

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.

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?

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!’

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 Tears. Journal 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 Park. Frontiers in Ecology and the Environment, 10: 466-7.

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

Generalist. Widespread. Solitary.

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.

Of all the Agapostemon, A. 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).

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.

Think 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.

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.