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FALL NUMBER 25 
THE BUMBLE BEES OF FLORIDA’ 
Ps We EFATTIC 
Altho there are 58 species of Bombidae in the U. S.,—47 of 
the genus Bombus—the true bumble bees, and 11 of Psithyrus— 
the parasitic bees; only five species, four Bombus and one Psi- 
thyrus, occur in Florida. Thus it is seen that these bees are but 
poorly represented in Florida. They are most abundant in the 
Rocky Mountains. The following key will enable the reader to 
separate our species. 
A. Outer surface of hind tibiae convex and hairy; face of males black 
Psithyrus. 
Abdomen of female entirely dark; that of male very variable... 
P. variabilis. 
AA. Outer surface of hind tibiae of female concave and smooth; face of 
mnvebe? stillet lvoe WEbUy ClO Wes = Scccs =e tei ae so tne es | oer ae Bombus. 
a. Thorax with a distinct black band. 
b. First and second segment of abdomen yellow....B. fraternus. 
fob. First, second and third segments of the abdomen yellow........ 
B. pennsylvanicus. 
aa. Thorax without a distinct black band. 
b. Dorsum of the abdomen with the first segment yellow and the 
nemainines seoments: flack. ....2 8 =e ee B. impatiens. 
bo. Dorsum of the abdomen with the first segment yellow, the 
second segment more or less brown-ferruginous on the basal 
portion, especially in the middle—the remaining segments 
Nee lee ean Sie ee Ty eed Sie’ DEN Oe Re Sree B. separatus. 
B. fraternus nests in the ground or in holes in stumps or trees 
at the level of the ground. It is one of the most pacific of the 
bumble bees. Its coloration is very constant. 
B. impatiens also nests in the ground. 
B. pennsylvanicus nests on top of the ground, usually in old 
mouse nests and similar situations. Occasionally the nests are 
subterranean. 
B. separatus nests in the grass on the surface of the ground. 
It is one of the most pugnacious of bumble bees when its nest is 
attacked. 
Bees of the genus Psithyrus are parasitic on the true bumble 
bees which they mimic in color and actions. Usually they mimic 
most closely the species of Bombus on which they are parasitic. 
The Psithyrus queen enters the Bombus nest and kills the queen. 
The young Bombus bees then adopt the Psithyrus queen, feed her 
and tend and raise her brood. 
1Abstract of a paper read before the Fla. Entomological Society March, 1920. 
