Hylaeus leptocephalus specialization

[Molly Jacobson]

Hi all,

It seems to be accepted knowledge that Hylaeus leptocephalus specializes on Melilotus spp (sweet clovers). But has there been extensive study on this?

I've been surveying the bees on our campus (SUNY ESF, Syracuse) for three years now and can safely say H. leptocephalus is the single most abundant bee we have on our grounds - more than honeybees or Bombus impatiens. And with the amount of specimens we've collected (172), it really makes me wonder how closely tied they really are with Melilotus. 

We have recorded females on 15 different plant species, and that is likely vastly undercounting as we see them on almost everything we look at but don't necessarily sweep - at some point we tired of pinning them all! In particular, flat-topped goldenrod seems, on our campus, to be a major congregation or lekking spot for males and females both, followed by large numbers on creeping thistle, goutweed, boneset, hemp dogbane, mountain mint, and milkweeds. Obviously not all of these could be providing pollen (e.g., milkweeds). But while we have sweet-clover on campus, it is not abundant, and not located very close to our gardens where we have collected the bulk of these bees.

Additionally, while sweet-clover has a pretty long bloom period (iNat suggests into November in some cases), it does not seem to bloom before July. We have recorded H. leptocephalus consistently every year emerging in mid-April, and active all season until late October. 

So with this, it seems interesting to me that they'd be considered so strictly dependent on Melilotus. If anyone else has noticed any patterns, or has insight, I'm really curious! 

Thanks,

Molly

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Molly Jacobson

M.S. Conservation Biology

Native Pollinator Ecologist

SUNY-ESF Restoration Science Center

Illick 255 | mmja...@esf.edu

[Molly Jacobson]

Sorry, quick addendum, since my pivot table lied to me. Our earliest recorded date for them is May 31, and latest is September 11. That is still a fair bit earlier than our Melilotus, which I checked for blooms last week and weren't even close yet.

-Molly

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Molly Jacobson

M.S. Conservation Biology

Native Pollinator Ecologist

SUNY-ESF Restoration Science Center

Illick 255 | mmja...@esf.edu

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From: 'Molly Jacobson' via beemonitoring <beemon...@googlegroups.com>
Sent: Saturday, June 20, 2026 8:08 PM
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Subject: [Beemonitoring] Hylaeus leptocephalus specialization

 

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[Molly Jacobson]

Sorry, to clarify - that's females. Males we've had emerge as early as May 6th, and don't seem to stick around past August.

-Molly

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Molly Jacobson

M.S. Conservation Biology

Native Pollinator Ecologist

SUNY-ESF Restoration Science Center

Illick 255 | mmja...@esf.edu

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From: 'Molly Jacobson' via beemonitoring <beemon...@googlegroups.com>

Sent: Saturday, June 20, 2026 8:13 PM

To: 'Parys, Katherine - REE-ARS' via beemonitoring <beemon...@googlegroups.com>

Subject: [Beemonitoring] Re: Hylaeus leptocephalus specialization

 

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[Nash Turley]

In Pennsylvania we have 3 recent Hylaeus leptocephalus records with host plant info, a female on Apocynum cannabinum and two males from Eupatorium serotinum

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