Modest masked bees (Hylaeus modestus modestus)

are barely 1/5" long -- and yet, this is the largest of the three species shown here. Modest masked bees appear in the park and Stone Barns in May, disappear in mid-summer and reappear in late August and September.  These bees are generalist pollinators, but in the park and Stone Barns, they are found most frequently feeding on goldenrod, Queen Anne's lace and carrot flowers.

​

Modest masked bees have yellow markings on all six legs (on the base of each tibia), and yellow markings on the sides of their thoraxes (on the tubercles).  They usually have a collar of yellow lining the front of the thorax (the pronotum); this trait aids in distinguishing them from some other yellow-faced bee species, such as Cresson's masked bee,

Modest masked bee females have two irregular yellow triangles on their faces, as shown in the photo strip here. On males, the yellow markings cover a larger area. Hylaeus modestus modestus is an eastern subspecies of Hylaeus modestus.  The bee's western counterpart, the subspecies H. modestus citrinifrons, has black front tibia, and females of that subspecies have more limited facial markings than the female Hylaeus modestus modestus.

​

Cresson's masked bees (Hylaeus mesillae cressonii)

are an eastern subspecies of the Mesilla masked bee (Hylaeus mesillae).  To the naked eye, Hylaeus mesillae resembles the modest masked bee discussed above --  but is much smaller, and lacks a yellow collar on the pronotum.  The female bee shown here was barely 1/6" long. Males tend to be smaller, and may be as tiny as 1/8".

The bee shown here was found foraging on goldenrod in mid-September, in a sandy area bordering a railroad access nine miles north of Rockefeller State Park Preserve.  (This species has not yet been documented in the preserve or Stone Barns). Mesilla masked bees feed on an extensive range of plants, although in our area, they commonly feed on goldenrod and Queen Anne's lace.

​

Slender-faced masked bees (Hylaeus leptocephalus)  have  been documented only once at Stone Barns, during late summer in a field containing legumes such as clover and bird's-foot trefoil.  This species is originally from Europe and not native to our area.  According to a 1970 article by entomologist Roy R. Snelling, the slender-faced masked bee appeared in North Dakota as early as 1912 and has since established itself in states throughout the country.

This tiny bee is a pollinator of elderberries and a range of other native flowering plants such as dogbane, heath aster, goldenrod and Queen Anne's lace.  The slender-faced masked bee, however, is unusual among yellow-face bees, because it shows a tendency toward specialization.  Slender-faced masked bees manifest a strong preference for plants of the legume family, especially Melitotus (sweet clover).  

​

The slender-faced masked bee has a narrow face shaped like an elongated trapezoid.  This bee has ivory rather than yellow markings, which appear on the bee's face, legs and thorax.  The male bee shown at right is minuscule -- barely 1/6" in length. Females are somewhat larger, at times topping 1/5".

Masked bees vs. wasps:  As noted, because they are slender and hairless, lack pollen-carrying structures and have black-and-yellow markings, yellow-faced bees are easily confused with wasps.  In particular, they superficially resemble two small wasps in our area --  the bee wolf (Philanthus) and the beetle wasp (Cerceris), which  often frequent the same plants as yellow-faced bees at Rockefeller Park and Stone Barns.  These wasps are shown in the photo strip at right.  They can be distinguished readily from yellow-faced bees, because the wasps have yellow stripes circling their abdomens.