The Bumble Bees are another recognizable group of flower lovers and pollen collectors. They are mostly social as are the honey bees with their division of labor into queens and drones and workers. The genus Bombus being the true bumble bees, there appear to be about 46 species in North America and about 20 in the eastern US. My working list for this genus in the east is here. Insect scientists have been fighting over the Bombus genus for years, arguing about genital spikes and horns, gaps and hairs. Ah me. But they are variable. And many can be separated by color and patterning of yellow and black. We'll just have to work on this.

For now, note 1) patterns of black on the thorax, 2) the yellow, orange and black banding arrangements on the abdominal segments and 3) color of the hair on the head segment. Don't know yet what species this is above.

Bumble from summertime. I think you can make out all the abdominal segment colors here and only the first appears yellow. This is the pattern for B. griseocollis but for now I am unsure.

I thought this was a Carpenter Bee in Xylocopa over on my Red Buckeye in spring. The Carpenters are still elusive despite drilling holes all over my deck.
The first time I went out with the camera and officially told myself I was going to shoot bumblebees. June 12th 2016. And I found only one species by appearance repeatedly. I captured one to look at under the microscope because I was unsure I could define one by visual appearances only. This one turned out to be in Group II, which seemed to make them all B. griseocollis. I was sort of stunned because the Bumblebees of North America book suggested that this species after 1996 went into rapid decline and is "very rare". Bugguide records belie this. And there are several records in AR after 2008. Louisiana records after 2015. I think the demise of this species was prematurely articulated.
The same shooting day, and the B. griseocollis were loving the White Prairie Clover. Ignoring most other flowrs at Camp Robinson WDA.  

And Norm's shot of likely the same species in his yard. Notable for the black head vestiture. And that cropped hair look with the dark hair on the abdomen beyond the first segments.  

 

Norm's shot of Bombus fervidus. Extensive yellow compared to the other species in our area. Also in group III. Extremes of form with extensive black on the anterior abdomen and all yellow thorax.  

This was B. auricomus by Norm's determination. A group III species. And one that may be more northern in the state. Note the yellow/black thoracic markings and no brown or orange anywhere. This would be a female and a queen. I will look at each of these more closely. But after Norm's shot below he had doubts. And I think we both believe this is a Bombus pensylvanicus now. It is still not clear fervidus will be common even in Norm's area. And the status of auricomus vs. pensylvanicus may be up in the air.  Bombus are tough from photos. But really in AR we only have eight to choose from.
Then Norm became less confident in shooting this pair. Also in the yard. One of which must be a Queen. That would be the one on the bottom here. And this is in late summer in Jonesboro area. I think this is a B. pensylvanicus pair. And one of Norm's side shots shows a slight orange tip on the male. I don't think fervidus ever has any orange on the tip of the yellow abdomen in the male. At least from the extensive color diagrams in BBs of NA.
Also from Norm's yard. A side shot of a male pattern again. And I think you can also see some orange on the very tip here. I have tried to convince Norm to take one bumblebee and put it under that nice scope of his.  
This is Bombus vagans. Also from Norm's area. And may not occur much out of northern AR. Note long yellow fuzziness extensively. Most forms with black final segments on the abdomen. This is a group I species with the lon cheek. 
Norm's calling this Bombus bimaculatus. It is another long haired species and tends to have those abdominal notches from above in several forms. And the central thoracic bald spot.  
This beauty was frisking the flowers in summer in Alaska. And Alaska has its own selection of fine bumbles including several with orange in the abdominal coloration. My best guess is a male B. flavifrons on this species.  
The west and north can be richer in Bombus species. Tom Lewis in Idaho probably has 15 or more species compared to our AR eight. Several are orange or red tinged. This beauty from July 2016 appears to be B. melanopygus. Sometimes nests in bird boxes apparently.