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A female Porter's Cuckoo Leafcutter Bee - Coelioxys porterae - (c) 2017 Sharp-Eatman Photo


Genus Coelioxys

A male Say's Cuckoo Leafcutter Bee - Coelioxys sayi - (c) 2016 Sharp-Eatman Photo

Cuckoo leafcutters invade leafcutter bee nests and deposit eggs in them.  When the cuckoo's young hatch, they eat the hosts' eggs or slaughter its young, and then devour the stores of nectar and pollen left by the mother leafcutter for her offspring.  The cuckoo larvae then mature within the nest, and later emerge as adults.  When such attacks occur late in the season, cuckoo larvae may spin cocoon-like structures inside of their hosts' nests and overwinter in them.


Many cuckoo bees of other types -- for example, Triepeolus  cuckoos (which usually prey on long-horned bees) and nomad bees (which usually prey on Andrena mining bees) -- are not closely related to the bees they parasitize.  Such cuckoos are shown on the cuckoo bee page of our guide.  We have chosen to feature leafcutter cuckoos immediately after the leafcutter section of this guide, however, because both belong to the same bee tribe and somewhat resemble each other.  Within that tribe, leafcutter cuckoos comprise a genus called Coelioxys; leafcutters belong to the genus Megachile. 


The Greek Coelioxys means "sharp belly," a genus name that refers to the tapered, pointed abdomens of cuckoo leafcutters.  As shown at right, female Coelioxys have spade-shaped abdominal tips that allow the cuckoos to break through the brood-cell walls that leafcutters construct with leaves, petals and other materials.  Male cuckoo leafcutters have abodomens armed with multi-pronged tips.

According to entomologist Charles D. Michener, members of the genus Coelioxys share the distinctive trait of having hairs on their eyes.  In addition, the wings of the cuckoo leafcutter bee have only two submarginal cells, and the back rim of the bee's scutellum (the second segment of the thorax) has prominent toothlike protrusions called axilla  (These traits are shown here in the photo strip.)

Genus Coelioxys  - Cuckoo Leafcutters

1/4" - 1/2"  (small to medium-sized)

A male Eight-toothed Cuckoo Leafcutter Bee - Coelioxys octodentata - (c) 2016 Sharp-Eatman Photo
Abdomen tip of a female Say's cuckoo leafcutter bee - (c) 2016 Sharp-Eatman Photo

Above left :   A  male Say's cuckoo leafcutter bee resting upside-down
Above right:   The pointed abdominal tip of a female cuckoo leafcutter
Below right:  The multi-pronged abdominal tip of a male cuckoo leafcutter
Below:   A modest cuckoo leafcutter gripping a stem with its jaws 

A female Porter's cuckoo leafcutter

of the Subgenus Cyrtocoelioxys 

Modest Cuckoo Leafcutter

Coelioxys  modestus

1/4" - more than 1/2" (small to medium-sized)

A female immaculate cuckoo leafcutter

Coelioxys modestus

Synocoelioxys leafcutter.  The male cuckoo leafcutter shown here belongs to the subgenus Synocoelioxys.  Synocoelioxys cuckoos prey specifically on leafcutters of the subgenus Sayapis -- such as the frugal, pugnacious and hostile leafcutters featured near the top of this page. 


Cuckoos of this subgenus are common visitors of aster-family flowers, such as sunflowers, cornflowers, and black-eyed Susans.  The bee shown here is feeding on rudbeckia. 


​Identification information:  Coelioxys  (Synocoelioxys) have black heads and thoraxes, and black abdomens encircled by white bands.  Their legs are reddish-brown and their eyes dark olive-green. A distinguishing trait of this subgenus is that the white bands on the bees' abdomens are interrupted in the middle.

At least three species of the subgenus Synocoelioxys have been documented in New York State:  Coelioxys alternatus, C. hunteri and C. texanus.


Family:  Megachilidae

Subfamily:  Megachilinae

Tribe:  Megachilini

Genus:  Coelioxys

Subgenus:  Synocoelioxys

Right:  A male
cuckoo leafcutter
of the subgenus 

Coelioxys (Synocoelioxys)
Immaculate Cuckoo Leafcutter Bee - Coelioxys immaculatus - (c) 2017 Sharp-Eatman Photo

Northern Cuckoo Leafcutters
of the subgenus Boreocoelioxys


Porter's Cuckoo Leafcutter

Coelioxys porterae
1/3" - 1/2" (medium-sized)

Say's Cuckoo Leafcutter

Coelioxys sayi
1/3" - 1/2" (medium-sized)

Eight-Toothed Cuckoo Leafcutter
Coelioxys octodentatus

3/10" - 1/2" (small to medium-sized)

Coelioxys porterae

A female Say's leafcutter gripping a mountain mint leaf with its mandibles

Coelioxys sayi
Coelioxys octodentus

A male eight-toothed cuckoo leafcutter raising its abdomen tip in the air

Immaculate cuckoo leafcutters (Coelioxys immaculata)  belong to the redundantly-named subgenus Coelioxys.  These cuckoo leafcutters parasitize the nests of Megachile addenda leafcutters (shown higher up on this page).  


During late spring of 2017, a large Megachile addenda aggregation appeared in the Rockwood Hall section of the park.  Immaculate cuckoo leafcutters appeared in large numbers on the fringes of the aggregation.  The cuckoos would park themselves two or three feet from a given hole and engage in the following behavior.  


The cuckoos would wait, deathly still, blending into the dirt-and-crushed-pebble background of the nest area, watching the behavior of the female leafcutters. The female leafcutters would arrive at the nests periodically, bearing leaves to construct egg chambers one-by-one and depositing eggs in each successively. Each time a targeted female leafcutter finished a chamber and emerged to fly off and gather more leaves and pollen, the immaculate cuckoo leafcutter watching the nest hole would sneak into  it like a burglar, presumably to pierce the outer wall of the newly-constructed egg chamber and to lay her own egg there. The cuckoo would then scamper from the hole a minute later and park again a few feet from the nest, awaiting the return of the female leafcutter bee.  This process would repeat itself throughout the day, assuring that the cuckoo bee deposited eggs in each of the individual nest chambers after the leafcutter had painstakingly provisioned them for her own offspring.

Immaculate cuckoo leafcutters forage on such plants as blackberries, raspberries, milkweed and false indigo.  The bees shown here were found feeding on cow vetch and clover.

​Identification information:  Immaculate cuckoo leafcutters have black heads and thoraxes; black abdomens banded with white hairs; and red legs with dark uppe segments.  Females' faces are covered with short white hairs and bordered on the bottom edge of the clypeus (lower face) with a row of pale orange hairs.  Females' eyes are green. A distinguishing trait of females of this species is the singular tip of the bee's abdomen -- shown in the photo here..



Family:  Megachilidae

Subfamily:  Megachilinae

Tribe:  Megachilini

Genus:  Coelioxys

Subgenus: Xerocoelioxys

Species:  Coelioxys immaculata

A female immaculate cuckoo leafcutter

Coelioxys immaculatus

An immaculate cuckoo leafcutter backing out of the hole of a Megachile addenda leafcutter

A female Immaculate Cuckoo Leafcutter Bee - Coelioxys immaculata - (c) 2017 Sharp-Eatman Photo


of the Subgenus Synocoelioxys


Modest cuckoo leafcutters (Coelioxys modestus)  belong to the subgenus Cyrtocoelioxys.  They are cleptoparasites of the belted leafcutter (Megachile centuncularis) and of the resin bee species Megachile campanulae wilmingtoni (a variation of the bellflower resin bee, found in coastal areas of the southeastern United States). Although neither of these host  bees has been documented in the preserve, it is likely that some belted leafcutters reside there, as this species is relatively common in the general New York area.


The two bees shown here illustrate the considerable size range of these bees.  The smaller one barely measured 1/3", while the larger one was nearly 3/5".


The small modest cuckoo leafcutter at right was found foraging on goldenrod during early September 2017.  The second, larger cuckoo (shown in the photo strip at right )was found outside the preserve -- in a public garden located in Riverdale, New York, 25 miles to the south of the preserve.  This bee was feeding on sneezewort in early August, 2017.

​Modest cuckoo leafcutters have been documented feeding on such plants as sunflowers, asters, ceanothus, sweet clover, sumac, verbena, bellflowers and mountain mint. 

​Identification information:  Modest cuckoo leafcutters have dark red legs or red-and-black legs; black heads and thoraxes; and black abdomens banded by pale hairs. The last segment of the female bee's abdomen is distinctive, as shown in the photo strip at right.  Female and male bees have dark brownish-green eyes.


​As noted, modest cuckoo leafcutters range greatly in size -- from just over 1/4 " to more than 1/2" inch long. Few leafcutters in our area run so small, and thus the bees' modest size aids in their identification.  The reverse is also true -- few cuckoo leafcutters in our area reach the 3/5" length of the second female bee shown here in the photo strip.

Three minute traits help identify females of this species:  (1) when viewed from the side, the upper half of the sixth segment (T-6) of the female bee's abdomen is upturned; (2) the lower half of the last segment (S-6) of the female bee's abdomen sports a fringe of hair; and (3) the first segment of the female bee's abdomen is edged with pale hairs along its front ridge. Male modest cuckoo leafcutters have multi-pronged abdominal tips.


Family:  Megachilidae

Subfamily:  Megachilinae

Tribe:  Megachilini

Genus:  Coelioxys

Subgenus:  Cyrtocoelioxys

Species:  Coelioxys modestus

of the Subgenus Coelioxys

Immaculate Leafcutter

Coelioxys  immaculatus
1/3" - 1/2" (medium-sized)

Coelioxys of the subgenus Boreocoelioxys are known as northern cuckoo leafcutter bees.  The vast number of cuckoo leafcutters found in Rockefeller State Park Preserve belong to this subgenus.  The park's northern cuckoo leafcutters are represented by at least three species:  Porter's cuckoo leafcutter; Say's cuckoo leafcutter; and the eight-toothed cuckoo leafcutter.

Porter's cuckoo leafcutters.  According to entomologist J.R. Baker's voluminous 1975 treatise, Taxonomy of Five Nearctic Subgenera of Coelioxys, Porter's cuckoo leafcutters invade the nests of relative leafcutters Megachile relativa) and frigid leafcutters (Megachile frigida).  Both of these leafcutter species are shown above. 


Porter's cuckoo leafcutters feed on such plants as geraniums, false indigo, hydrangea, cranberries, blueberries, goldenrod and asters.   The Porter's cuckoo leafcutters featured here were found drinking nectar from coreopsis and butterfly weed in the park's Visitor Center garden in late June and early July of 2017. These bees are relatively uncommon in the park.


Say's cuckoo leafcutters are the most common Coelioxys cuckoo bees found in the park.  These cuckoos target the nests of flat-tailed leafcutter bees (Megachile mendica) (shown above).  Sometimes, after the cuckoo's eggs have been deposited in flat-tailed leafcutter brood cells, the newly hatched cuckoos coexist with their prey, sharing the provisions left by the mother flat-tailed leafcutter.  Field studies have documented Say's cuckoo leafcutters and flat-tailed leafcutters emerging from the same nest.  


Say's cuckoo leafcutters drink nectar from a very wide array of flowering plants, among them, blackberries, melons, squash and sunflowers.  The Say's cuckoo leafcutters shown here were found feeding in the park in July and August on orange butterfly weed, mountain mint and goldenrod. 

Eight-toothed cuckoo leafcutters, like Says' cuckoo leafcuttters, infiltrate the nests of flat-tailed leafcutter bees.  Eight-toothed cuckoo leafcutters also have been documented parasitizing the nests of at least four other leafcutter species:  the common little leafcutter  (Megachile brevis), the Texas leafcutter (Megachile texana), the alfalfa leafcutter (Megachile rotundata)  and the belted leafcutter (Megachile centucularis).  (The first three of these are shown above.)


Eight-toothed leafcutters forage on a broad range of wildflowers and native plants, among them elderberry, sumac, wild asters, onions and Virginia creeper.  The male bee shown here was feeding on goldenrod on a sunny park trail in early September.

​Identification information:   All three of these northern cuckoo leafcutter species have dark abdomens banded by short pale hairs; thoraxes with prominent axillae; red, black or red-and-black legs; and green eyes.  Females of these species have pointed, conical abdomens with spearlike tips.  Males have impressive abdominal tips terminating in multiple prongs.  Male Boreocoelioxys found in our area lack foveae (depressions) on the sides of their third abdominal segments.

Porter's cuckoo leafcutters are striking, long-bodied bees. They have all-black legs, a trait that makes them readily distinguishable from Say's and eight-toothed leafcutters. Other traits of Porter's leafcutters, visible only on minute inspection, include the following:  (1) females have distinctive abdominal tips with tooth-like notches near the ends; (2) and they sport relatively long hairs on their eyes.  (3) The abdomen of the male C. porterae also has  prominent depressions on the first segment (T-1); and an unpitted line dividing the fourth and fifth segments (T-4 and T-5)  (These traits are shown here in the first photo strip.)

Say's and eight-toothed cuckoo leafcutters have predominantly red legs and dark wings.  The bees' tegulae (located where the wing joins the bee's body) are red. Both Say's and eight-toothed cuckoo leafcutter males have deep grooves that traverse the second and third segments of their abdomens (T-2 and T-3). On Say's leafcutters, these grooves may be interrupted in the middle.

These two species differ subtly (as shown hdfd in the second photo strip):  (1) The female Say's cuckoo leafcutter has a distinctive clypeus (the face part above the jaws)  with a shallow U-shaped lower rim.  On female eight-toothed leafcutters, the lower rim of the clypeus runs straight across.  (2) Male and female Say's leafcutters have legs that are black near the base and reddish on the lower segments.  Eight-toothed leafcutters, by contrast, usually have entirely red (or mostly red) legs.



Family:  Megachilidae

Subfamily:  Megachilinae

Tribe:  Megachilini

Genus:  Coelioxys

Subgenus:  Boreocoelioxys

Species:  Coelioxys sayi, Coelioxys octodentata
   and  Coelioxys octodentatus

This website's photos and text are protected by registered copyright. All photos are © 2014-2017 Paula Sharp & Ross Eatman, all rights reserved.  To inquire about possible use of photos, see Permissions. 


REFERENCES:  For a comprehensive list of references used in compiling this guide, click here:

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