Paracantha gentilis: Difference between revisions

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'''''Paracantha gentilis''''' is a species of tephritid or fruit fly in the genus ''[[Paracantha]]'' of the family [[Tephritidae]]. It has a widespread distribution throughout the [[Western United States]],<ref name=":8">{{Cite book|last1=Foote|first1=Richard H. |url= https://essig.berkeley.edu/documents/cis/cis07.pdf|title=The Fruit Flies or Tephritidae of California|last2=Blanc|first2=F. L. |publisher= [[University of California Press]] |year=1963|series=Bulletin of the California Insect Survey|volume=7|location=Berkeley and Los Angeles}}</ref> and has also been found as far south as Mexico and Costa Rica.<ref name="SysDatabase1999" /> It most closely resembles ''[[Paracantha culta]]'', which is widespread in the [[Southeastern United States]], but ''P. gentilis'' can be distinguished by having smaller spots on the head.<ref name=":7">{{Cite book|last1=Foote|first1=R. H. |url=http://worldcat.org/oclc/1193309456 |title=Handbook of the Fruit Flies (Diptera: Tephritidae) of America North of Mexico|last2=Blanc|first2=F. L.|last3=Norrbom|first3=A. L.|publisher=[[Cornell University Press]]|year=1993|isbn=978-1-5017-3461-8|oclc=1193309456}}</ref>

''Paracantha gentilis'' was first described by [[Erich Martin Hering]] in 1940 from a pair of male and female specimens collected in [[Wyoming]].<ref name="Hering1940" /> In the same publication, he described ''Paracantha sobrina'' from a single female specimen collected in Costa Rica.<ref name="Hering1940" /> The following year, [[John Russell Malloch]] revised the genus ''Paracantha'', and described three new speciestaxa: ''P. mimetica'', ''P. mimetica elongata,'', and ''P. mexicana''.<ref name="Malloch1941" /> These descriptions all largely relied on wing pattern characters rather than terminalia.

In 1953, Martin Ladislau Aczél again revised the genus ''Paracantha'' of the [[Americas]], and found that these Malloch's speciesnew taxa of ''Paracantha'' could all be synonymized with ''Paracantha gentilis''. Once more specimens were collected and examined, and the variation in wing pattern that were used to delimit species represented a gradient of variability rather than discrete groups, and as such Aczél moved ''mimetica'', ''mimetica elongata,'', and ''mexicana'' to synonymy with ''gentilis''.<ref name="Aczel1953" /> These synonymies were confirmed by researchers constructing a systematic database of Tephritidae, but in addition the species ''Paracantha sobrina'' was synonymized with ''gentilis''; no reasoning is given.<ref name="SysDatabase1999" />

Once first instar ''P. gentilis'' larvae hatch from eggs, each tunnels to a separate floral tube within the immature capitula[[Capitulum (flower)|capitulum]]<ref name=":15">{{Cite journal|last1=Headrick|first1=David|last2=Goeden|first2=Richard D.|date=1990-07-01|title=Life History of Paracantha gentilis (Diptera: Tephritidae)|url=http://dx.doi.org/10.1093/aesa/83.4.776|journal=Annals of the Entomological Society of America|volume=83|issue=4|pages=776–785|doi=10.1093/aesa/83.4.776|issn=1938-2901}}</ref> and only feeds there for that life stage.<ref name=":13" /> Unlike many other Tephritidae, even species in Europe that use ''Cirsium'' capitula like ''[[Urophora solstitialis]],'' ''P. gentilis'' does not cause host plants to form galls or host-tissue growth.<ref name=":13" /> At this stage, the median oral lobe is not well defined.<ref name=":12" /> First instar larvae always have four spiracular bundles with unbranched hair, which is a character shared with ''[[Rachiptera limbata]]'', a member of a genus closely related to ''Paracantha''.<ref name=":16">{{Cite journal|last=Frías|first=Daniel|date=October 2008|title=Morphology of immature stages in the neotropical nonfrugivorous Tephritinae Fruit Fly Species Rachiptera limbata Bigot (Diptera: Tephritidae) on Baccharis linearis (R. et Pav.) (Asteraceae)|journal=Neotropical Entomology|volume=37|issue=5|pages=536–545|doi=10.1590/s1519-566x2008000500006|pmid=19061038 |issn=1519-566X|doi-access=free}}</ref>''.''

Second-instar larvae are similar to the first-instar larvae, but have more [[Sclerite|sclerotized]] mouth hooks<ref name=":12" /> than before. This is possibly to assist in their changed food source, as they leave the floral tube and tunnel through more hardyhardened plant material totowards the outer margin of the capitulacapitulum.<ref name=":13" />

This larval stage avoids intraspecific competition for plant resources based on the density of third-instar ''P. gentilis'' larvae within a given capitulacapitulum. The first few third-instar larvae will feed at the central ovules of the plant, directly eating plant tissue. When about three to four third-instar larvae are present, they will start moving to the upper receptacle of the capitulacapitulum and create depressions in the surface. In this area, they use the median oral lobe for liquid food uptake, extracting sap from the depressions in the upper receptacle.<ref name=":13" />

Reproductively mature ''Paracantha gentilis'' adults spend most of their time on ''Cirsium'' plants. Both sexes feed on sap at oviposition wounds in thistles, and defend these sap sites from [[ant]]s by lunging at the intruders while audibly buzzing their wings. When not defending, ''P. gentilis'' engages in "agnostic" wing behavior, consisting of slow and asynchronous movements that seemingly don't act as communication.<ref name=":15" /> Adults also engage in "bubbling", where liquid is ejected as a bubble from the mouth and then sucked back in; this may act as a method of temperature regulation.<ref>{{Cite journal|last1=Gomes|first1=Guilherme|last2=Köberle|first2=Roland|last3=Von Zuben|first3=Claudio J.|last4=Andrade|first4=Denis V.|date=2018-04-19|title=Droplet bubbling evaporatively cools a blowfly|journal=Scientific Reports|volume=8|issue=1|page=5464 |doi=10.1038/s41598-018-23670-2|pmid=29674725 |bibcode=2018NatSR...8.5464G |issn=2045-2322|doi-access=free|pmc=5908842}}</ref>

In California, it has been shown that ''Cirsium'' flowerheads are attacked by multiple waves of herbivores. ''Paracantha gentilis'' was is often the first insect to reach the capitula and oviposit, followed by ''Terellia occidentalis'', then ''[[Phycitodes mucidella]]. P. gentilis'' appears to avoid interspecific competition through attacking earlier than these other two species, and only using the center of the capitula. ''P. gentilis'' also gradually surrounds itself with a mixture of dried feces and plant debris, which protects the third instar larval form and puparium.<ref name=":13" />