Figures
Fig. 1: Antenna
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Forewing, base of fore wing with alula
Fig. 6: Sternites V - VII
Fig. 7: Tergites V - VII
Fig. 8: Tergites VII - IX
ITS-RFLP gel patterns (1&8 ladder, 2 PCR-product, 3 RSAI, 4 HaeIII, 5 MspI, 6 HinfI, 7 AluI)
Fig. 9: Primer pair 18SMP/28SMP
Taxonomic Information
Species:
Scirtothrips perseae Nakahara, 1997
Common name:
Avocado thrips
Present taxonomic position:
Family: Thripidae Stephens, 1829
Subfamily: Thripinae (Stephens) Karny, 1921
Genus: Scirtothrips Shull, 1909
Species Recognition
General information about the genus Scirtothrips:This genus contains about 60 species all having rows of microtrichia on the lateral sides of the tergites and a complete comb on tergite VIII. These are small, pale yellow thrips with eight segmented antennae and segments III and IV have forked sense cones. The pronotum on these thrips is closely and transversely striate and most have spotted areas interrupting the striae. The forewings are narrow with only a few distal setae on the first vein and a few apical setae on the hind vein.
Typical character states of Scirtothrips perseae:
Body color
Mainly pale or yellow, with some darker markings
Antennae
Number of antennal segments: 8
Segment IV - forked sensorium: scarcely extending beyond base of segment V
Segments II and III shape: more or less symmetric
Segments III & IV sensoria: emergent and forked
Base of sensorium on antennal segment VI: no more than 2 times as wide as base of nearest seta
Terminal antennal segments: rarely elongate
Head:
Distance between bases of ocellar setae III: less than width of first ocellus
Head shape between compound eyes: not prolonged
Ocellar setae III on head: arising on anterior margin of, or in front of, ocellar triangle or arising within ocellar triangle anterior to tangent of anterior margin of hind ocelli
Postocular setae I: present
Surface of head, pronotum and fore legs: without strong reticulate sculpture
Ocellar setae I in front of anterior ocellus: present
Prothorax
Number of pairs of elongate pronotal setae: 0-3
Number of pairs of elongate posteroangular pronotal setae: 1-2
Pronotum shape: rectangular
Mesothorax
Mesothoracic endofurca: with median spinula
Metathorax
Metanotal median area sculptured lines: transverse at anterior, but forming irregular longitudinal reticulations on posterior half
Metanotal median setae position: arising behind anterior margin
Metanotum: with campaniform sensilla
Metanotum major sclerite: with two major sclerites, metascutum and metascutellum
Metanotum median area: with no equiangular reticulation
Metanotum sculpture: without dominant sculptured triangle medially
Metathoracic endofurca: transverse, sometimes with simple median spinula
Wings
Wings: present and more than half as long as abdomen
First vein of forewing: distinct from costal vein
Forewing anterior margin: with setae and cilia but cilia longer than setae
Forewing color: uniformly light brown or uniformly pale or weakly shaded
Forewing costal fringe of cilia: arising at anterior margin of wing
Forewing costal setae at middle of wing: shorter than median width of wing
Forewing first vein setal row: incomplete, with setae not closely and uniformly spaced
Forewing posterior margin cilia: undulated near apex
Forewing second vein setal row: incomplete, with setae not closely and uniformly spaced
Forewing surface: not reticulate
Forewings: with veins, setae and microtrichia
Legs
Fore tibial apex: not extending around fore tarsus
Mid and hind tarsi: with two segments
Abdomen:
Abdominal segment X: never tubular, longitudinally incomplete ventrally in both sexes
Abdominal sternite III of female: without glandular areas
Abdominal sternite VII: with marginal setae but no discal setae
Abdominal sternite VII median marginal setae: arising at margin
Abdominal sternites IV , V and VI: with marginal setae but no discal setae
Abdominal sternites V & VI microtrichia: restricted to lateral thirds of discal area
Abdominal tergites: without curved wing-retaining setae
Abdominal tergites IV & V median setal pair: longer than distance between their bases
Abdominal tergites V-VII: without paired ctenidia, sometimes with irregular microtrichia
Markings on tergites IV to VI: with shaded areas laterally and antecostal ridges dark
Setae on abdominal tergite X: slender
Surface of lateral thirds of abdominal tergites: with many regular rows of fine microtrichia
Ctenidia on tergite VIII: not present, but groups of microtrichia
Tergite VIII posteromarginal comb of microtrichia: present, complete medially
Tergite VIII posteromarginal microtrichia: long, slender and regular
Biology
Life history:
The developmental time from egg to adult has been studied in Scirtothrips perseae by Mark Hoddle (2002) who examined the developmental time under several temperatures ranging from 15°C to 30°C (Hoddle, 2002). In summary the range for development time was 18 to 49 days.
Host plants:
Avocado (Persea
americana)
Vector capacity:
None identified
Current known distribution:
Central and South America, North America
Additional notes:
All of the members of this group feed on the leaves of their plant hosts and are quite cryptic in habit. Scirtothrips perseae feeds on the newly developing avocado fruit reducing the fruit from high quality fresh market avocados to processing for guacamole at a significant reduction in crop value in California (Nakahara, 1997).
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Links:
Mound, LA (2005): Thysanoptera (Thrips) of the World
- A Checklist. http://www.ento.csiro.au/thysanoptera/worldthrips.html