Honeydew (secretion)

{{short description|Sugar-rich liquid}}

File:Ant Receives Honeydew from Aphid.jpg produces honeydew for an ant in an example of mutualistic symbiosis.]]

File:Honeydew on a leaf (cropped).jpg

File:Dolichovespula_maculata_sips_nectar_from_Disholcaspis_quercusmamma_gall.jpg sips honeydew from a Disholcaspis quercusmamma gall covered by sooty mold]]

File:Brood XIII-Magicicada cassini-male peeing honeydew.webm "cicada rain" slow motion]]

Honeydew is a sugar-rich sticky liquid, secreted by aphids, some scale insects, and many other true bugs and some other insects as they feed on plant sap. When their mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the anus of the insects, allowing them to rapidly process the large volume of sap required to extract essential nutrients present at low concentrations. Honeydew is particularly common as a secretion in hemipteran insects and is often the basis for trophobiosis.{{cite journal | vauthors = Delabie JH | date = 2001 | title = Trophobiosis Between Formicidae and Hemiptera (Sternorrhyncha and Auchenorrhyncha): an Overview. | journal = Neotropical Entomology | volume = 30 | issue = 4 | pages = 501–516 | doi = 10.1080/00222930150215378 | bibcode = 2001JNatH..35..279F | s2cid = 84918015 | url = http://www.scielo.br/pdf/ne/v30n4/a01v30n4.pdf }} Some caterpillars of Lycaenidae butterflies and some moths also produce honeydew.{{cite journal|title=Ants feeding on anal exudate from tortricid larvae: a new type of trophobiosis|vauthors=Maschwitz U, Dumpert K, Tuck KR |journal=Journal of Natural History|volume=20|issue=5|year=1986|doi=10.1080/00222938600770751|pages=1041–1050|bibcode=1986JNatH..20.1041M }} In addition to various sugars, honeydew contains small amounts of amino acids, other organic compounds, and inorganic salts with its precise makeup affected by factors such as insect species, host plant species, and whether a symbiotic organism is present.{{cite journal |last1=Shaaban |first1=Basel |last2=Seeburger |first2=Victoria |last3=Schroeder |first3=Annette |last4=Lohaus |first4=Gertrud |date=24 January 2020 |title=Sugar, amino acid and inorganic ion profiling of the honeydew from different hemipteran species feeding on Abies alba and Picea abies |journal=PLOS ONE |volume=15 |issue=1 |pages=e0228171 |doi=10.1371/journal.pone.0228171 |doi-access=free|pmid=31978201 |pmc=6980476 |bibcode=2020PLoSO..1528171S }}

Honeydew-producing insects, like cicadas, pierce phloem ducts to access the sugar rich sap; the excess fluid released by cicadas as honeydew is called "cicada rain".{{cite news |author=Elle Hunt |date=26 May 2021 |url=https://www.theguardian.com/environment/2021/may/26/sex-mad-and-spectacular-17-incredible-facts-about-cicadas |title=Sex-mad and spectacular: 17 incredible facts about cicadas |newspaper=Guardian US }}{{cite news |author1=John Dodge |author2=Noel Brennan |date=May 15, 2024 |url=https://www.cbsnews.com/chicago/news/cicada-urine-pee-science-discovery-emergence/ |title=Cicadas pee from trees. And they can urinate a lot, a new study finds |newspaper=CBS NEWS }} The sap continues to bleed after the insects have moved on, leaving a white sugar crust called manna.{{cite book | vauthors = Lee AK |title=Evolutionary Ecology of Marsupials |publisher=Cambridge University Press |page=33 |url=https://books.google.com/books?id=47-a-3_1aM4C&pg=PA33 |access-date=25 August 2019|isbn=9780521252928 |date=1985-03-21 }} Ants may collect, or "milk", honeydew directly from aphids and other honeydew producers, which benefit from their presence due to their driving away predators such as lady beetles or parasitic wasps—see Crematogaster peringueyi. Animals and plants in a mutually symbiotic arrangement with ants are called Myrmecophiles.

In Madagascar, some gecko species in the genera Phelsuma and Lygodactylus are known to approach flatid plant-hoppers on tree-trunks from below and induce them to excrete honeydew by head nodding behaviour. The plant-hopper then raises its abdomen and excretes a drop of honeydew almost right onto the snout of the gecko.{{cite journal | vauthors = Fölling M, Knogge C, Böhme W | title = Geckos are milking honeydew-producing planthoppers in Madagascar | journal = Journal of Natural History | date = February 2001 | volume = 35 | issue = 2 | pages = 279–84 | doi = 10.1080/00222930150215378 | bibcode = 2001JNatH..35..279F | s2cid = 84918015 }}

Honeydew can cause sooty mold on many ornamental plants. It also contaminates vehicles parked beneath trees, and can then be difficult to remove from glass and bodywork. Honeydew is also secreted by certain fungi, particularly ergot.[https://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/Ergot.aspx Ergot of Rye] {{Webarchive|url=https://web.archive.org/web/20180809062656/https://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/Ergot.aspx |date=2018-08-09 }}, APSnet.org, The American Phytopathological Society Honeydew is collected by certain species of birds, mosquitoes,{{cite journal | vauthors = Peach DA, Gries R, Young N, Lakes R, Galloway E, Alamsetti SK, Ko E, Ly A, Gries G | display-authors = 6 | title = Aedes aegypti (L.) to Aphid Honeydew | journal = Insects | volume = 10 | issue = 2 | pages = 43 | date = February 2019 | pmid = 30717169 | pmc = 6409638 | doi = 10.3390/insects10020043 | doi-access = free }}{{cite journal| vauthors = Peach DA, Gries G |title=Mosquito phytophagy – sources exploited, ecological function, and evolutionary transition to haematophagy|journal=Entomologia Experimentalis et Applicata|language=en|doi=10.1111/eea.12852|issn=1570-7458|year=2019|volume=168|issue=2|pages=120–136|doi-access=free}} wasps, stingless bees{{cite journal | vauthors = Koch H, Corcoran C, Jonker M | title = Honeydew Collecting in Malagasy Stingless Bees (Hymenoptera: Apidae: Meliponini) and Observations on Competition with Invasive Ants | doi = 10.4001/003.019.0111 | journal = African Entomology | volume = 19 | issue = 1 | pages = 36–41 | year = 2011 | s2cid = 83522254 | url = http://www.tb1.ethz.ch/PublicationsEO/PDFpapers/Koch_AFRICAN_ENTOMOLOGY_2011_19_36-41.pdf | archive-url = https://web.archive.org/web/20120319183744/http://www.tb1.ethz.ch/PublicationsEO/PDFpapers/Koch_AFRICAN_ENTOMOLOGY_2011_19_36-41.pdf | url-status = dead | archive-date = 2012-03-19 }} {{closed access}} and honey bees, which process it into a dark, strong honey (honeydew honey). This is highly prized in parts of Europe and Asia for its reputed medicinal value. Parachartergus fraternus, a eusocial wasp species, collects honeydew to feed to their growing larvae.{{cite journal | first1 = Mateus | last1 = Sidnei | first2 = Fernando Barbosa | last2 = Noll | first3 = Ronaldo | last3 = Zucchi | name-list-style = vanc | title = Caste Flexibility and Variation According to the Colony Cycle in the Swarm-founding Wasp, Parachartergus Fraternus (Gribodo) (Hymenoptera: Vespidae: Epiponini) | journal = Journal of the Kansas Entomological Society | volume = 77 | issue = 4 | date = 2004 | pages = 470–83 | doi = 10.2317/E-40.1 | s2cid = 84967255 }} Recent research has also documented the use of honeydew by over 40 species of wild, native, mostly solitary bees in California.{{cite journal | vauthors = Meiners JM, Griswold TL, Harris DJ, Ernest SK | title = Bees without Flowers: Before Peak Bloom, Diverse Native Bees Find Insect-Produced Honeydew Sugars | journal = The American Naturalist | volume = 190 | issue = 2 | pages = 281–291 | date = August 2017 | pmid = 28731796 | doi = 10.1086/692437 | bibcode = 2017ANat..190..281M | s2cid = 206004844 }}