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Diagnostic Methods
for
Poinsettia thrips
Echinothrips americanus
This Diagnostic Protocol can be constantly updated and is only correct at time of printing (Friday
5th of May 2017 at 08:28:37 PM).
The website http://www.padil.gov.au/pbt should be consulted to ensure you have the most
current version before relying on the information contained.
Introduction
The Poinsettia Thrips, Echinothrips americanus Morgan, is a member of a small genus of
Thripidae that is native to the warmer areas of eastern America. Described originally from
Florida and known to be native throughout much of eastern North America, it has been
introduced to Hawaii and has become widely distributed by the horticultural trade throughout
much of Europe, from Ireland in the West, to Sweden. Norway and Poland in the North, and
Bulgaria, Croatia and Italy in the East and South (Vierbergen et al. 2006). Moreover, it has been
seen from Thailand, is established in Japan, has been intercepted in quarantine in Taiwan, and
can be expected to be introduced to yet further countries, including Australia, in association with
the widespread trade and transport of particular species of decorative house plants.
As a member of the family Thripidae, adults of this thrips have two pairs of slender wings that
bear marginal fringes of long cilia. In contrast to most members of this family, the setae on the
longitudinal veins on the front pair of wings are unusually long and prominent. The body is dark
brown but, in contrast to the common Greenhouse Thrips that also has the head with reticulate
sculpture, the internal pigment of the body is bright red, and the forewings have transverse light
and dark coloured bands.
In its native range, this thrips is particularly associated with Impatiens plants, but in greenhouses
it breeds readily on plant species from a wide range of families. It is considered a pest on
Poinsettia (Euphorbia pulcherrima) as well as various Araceae such as Diffenbachia and
Syngonium that are grown for their ornamental foliage, although it often causes little obvious
damage. In the Netherlands it is reported as a pest of Capsicum crops grown in greenhouses, and
establishes considerable populations on common glasshouse weeds such as Cardamine hirsuta.
In Thailand, a considerable population was found breeding on the weed, Eichornia crassipes
(water hyacinth). Despite being usually bisexual, this thrips is reported to breed
parthenogenetically, with virgin females having been reported to produce both sexes (Oettingen
& Beshear, 1994). This method of breeding, and the unusually wide host range, combined with
the ability to develop considerable populations on certain plants without obvious damage to the
leaves, increases the probability that the species will become established in further areas.
Although this thrips is not known to vector any plant viruses, feeding activity by larvae and
adults results in small chlorotic areas on leaves with some shriveling of leaves. Moreover, soiling
of leaves occurs with small black faecal droplets, and these are similar to those associated with
the Greenhouse Thrips, Heliothrips haemorrhoidalis. Although not at all closely related, these
two species appear to share the habit of feeding primarily on older leaves, not on young, rapidly
growing tissues. In greenhouses in the Netherlands, a considerable array of predators of
Echinothrips americanus has been reported in association with various crops (Van Scheldt et al.,
2002). These include three species of Aeolothripidae (Aeolothrips tenuicornis, Franklinothrips
orizabensis, F. vespiformis), one species of Phytoseiidae (Amblyseius limonicus), two species of
Anthocoridae (Orius laevigatus, O. majusculus), one species of Lygaeidae (Geocoris punctipes),
two species of Miridae (Dicyphus hesperus, Macrolophus caliginosus), and one species of
Chrysopidae (Chrysoperla carnea). Of these, M. caliginosus was considered to be the most
effective at limiting population growth of E. americanus.
Biology
Stages of Development
Life History
Female E. americanus deposits eggs separately in slits in the leaf tissue, at random on the leaf
surface. Developmental time depended on temperature, at 15°C the egg stage averaged 15.5 days
and the immature stage required 18.4 days, totalling 33.9 days. Under warmer conditions
development was faster; at 30°C the egg stage took 5.8 days and the immature stage only 5.6
days for a total of 11.4 days from egg to adult. Developmental time varied with different host
species. All stages were present throughout the year in the greenhouse. Adults and immature
stages were not very active and would remain in the same area of a leaf for days if not disturbed.
Lifestages
Adult:
The adult female Echinothrips americanus is about 1.6 mm long and the male about 1.3 mm
long. The general body colour is dark brown with red between the abdominal segments.
Segments 1 and 2 of the antenna are dark brown, and segments 3 and 4 are lighter. Forewings are
pale grey at base, middle, and tip with light brown in between.
Egg:
The egg is laid in the plant tissue, and is elongate and clear to white in colour.
Larva:
Immediately after the larvae hatch they are clear, but they change to white and then become light
or pale yellow after feeding. The second-stage larvae become cream coloured before moulting to
the pre-pupae stage.
Pupa and Pre-pupa:
Both are found on leaf tissue and move only when disturbed. Pre-pupa is white with short wing
pads and antennae extend forward. The pupa is white with long wing pads with the antennae bent
back over the body.
Host Range
Echinthrips americanus have been found and reproduce on most ornamental plants tested and
many of the common weed species of Georgia. In an experiment in Georgia, out of 51 species of
cultivated plants and 75 native plants studied, feeding and reproduction was observed on 40
cultivated and 59 native species. Of all the greenhouse host plants; poinsettias, Irish shamrock,
and impatiens are the most common hosts in Georgia. They also have been common on
chrysanthemum foliage and flowers. They also have been a pest on woody ornamentals. They
have also been seen on Ficus, Neanthe Bella palms and Devil's Ivy.
Genera of plants frmo which Echinothrips americanus has been recorded.
Agavaceae
Apiaceae
Cordyline
Arracacia
Araceae
Anthurium
Cryptocoryne
Dieffenbachia
Homalomena
Philodendron
Spathiphyllum
Syngonium
Dendranthema
Polymnia
Asteraceae
Liliaceae
Impatiens
Betula
Cardamine
Euphorbia
Acalypha
Cassia
Desmodium
Mimosa
Phaseolus
Asparagus
Magnoliaceae
Malvaceae
Moraceae
Myricaceae
Myrtaceae
Onagraceae
Veratrum
Magnolia
Hibiscus
Ficus
Myrica
Psidium
Ludwigia
Balsaminaceae
Betulaceae
Brassicaceae
Euphorbiaceae
Fabaceae
Orchidaceae
Oxalidaceae
Passifloraceae
Poaceae
Pontederiaceae
Primulaceae
Rosaceae
Rubiaceae
Solanaceae
Urticaceae
Vitaceae
Bletilla
Oxalis
Passiflora
Bambusa
Hordeum
Eichornia
Lysimachia
Prunus
Rubus
Coffea
Capsicum
Pilea
Cissus
Distribution
Distribution
Echinothrips americanus has a range over most of the eastern United States. It has been reported
as a pest of nursery and landscape plants in the southern part of its range and as a greenhouse
pest on several plants. It has been reported in the Netherlands (Vierbergen 2001), Austria
(Kahrer and Lethmayer 2000) and Italy (Marullo and Pollini 1999).
Potential distribution in Australia
Likely to become readily distributed through glasshouses.
Transmission
Flight, walking or human assisted on affected fresh plant material.
Risk Analysis
Entry potential
Entry potential: Rating = MEDIUM
Thrips in general are often intercepted at the border.
Establishment potential
Establishment potential: Rating = HIGH
A range of plants commonly found in Australia can act as hosts for Echinothrips americanus.
The similar climates to Eastern USA and Europe that are available in parts of Australia, and the
glasshouse growth of many host species would suggest that this species would readily establish.
Thrips can have a high reproductive potential even in the absence of males e.g. under glasshouse
conditions Frankliniella occidentalis can have 15 generations per year with females producing
20-40 eggs each.
Existing control programs may be effective for some hosts (e.g. broad spectrum pesticide
applications) but not all hosts.
Spread potential following establishment
Spread potential following establishment: Rating = HIGH
Natural physical barriers (e.g. deserts/arid areas) may prevent these pests spreading unaided but
adults are capable of flight and adults and immature forms may spread undetected via the
movement of fruit or infested vegetative host material.
The relevance of natural enemies in Australia is not known.
Economic impact
Economic impact: Rating = MEDIUM
Wide host range so would affect a range of species. Different populations of this thrips have
expressed different susceptibility to insecticides, so resistant varieties would likely adversely
impact IPM programs. Greenhouse populations in Georgia have been susceptible to most
insecticides. There have been reports of populations on woody nursery plants that were difficult
to control.
May transmit viruses but no data is available.
Environmental impact
Environmental impact: Rating = NEGLIGIBLE
No known environmental impacts are known for this species, though it is possible that it might
impact of native species within its how range.
CONCLUSIONS
Overall risk: Rating = MEDIUM
Economic impact "D" and environmental impact "B", total likelihood rated MEDIUM, so total
combined risk = MEDIUM.
Taxonomy
Classification
Kingdom Animalia
Phylum Arthropoda
Class Insecta
Order Thysanoptera
Family Thripidae, Subfamily Thripinae
Only seven species are described in the genus Echinothrips, all from the Americas, and of these,
only E. americanus has become widespread.
One species is known only from eastern North America where it lives on the needles of trees of
the gymnosperm genus Tsuga. The other five species are from Central America or South
America. Two of these remain known only from single specimens collected in southern Brazil,
and a third is specific to a species of the lycophyte genus, Selaginella, and is known only from
Costa Rica (Mound & Marullo, 1996).
The other two species are widespread in the Caribbean area. Both appear to be polyphagous, and
one of them apparently extends southwards to Brazil as a sporadic pest of soybeans.
Name and Synonyms
Correct name: Echinothrips americanus Morgan, 1913
One available synonym: Dictyothrips floridensis Watson, 1919
Detection
Detection Method
This species is likely to be detected only by direct observation of the black adults, because
damage to the leaves of plants is sometimes minimal. Feeding damage can result in small
chlorotic areas, but these can be very similar to the damage caused by an attack of leaf-feeding
mites.
This thrips may be found feeding on both the upper and lower surfaces of leaves, indeed on any
green tissues, and on some soft leaved plants feeding may result in leaf distortion. The species is
not usually associated with flowers, nor with very young leaves. The larvae produce droplets of
dark faecal material, thus soiling the leaves, but this damage is similar to that produced by the
larvae of the common Greenhouse Thrips, Heliothrips haemorrhoidalis (Oetting & Beshear,
1994).
Detection is therefore dependent on careful visual inspection, preferably supplemented by use of
a hand lens or head-mounted magnifier. The immatures are sluggish in their movements, and the
two larval stages are followed by two pupal stages. All of these are pale yellow to orange in
colour, with faint brown areas, but they are not readily seen until an operator has experience in
developing a personal 'search image' for them.
As with other thrips species, the quickest method of discovering these insects on a plant is to beat
the leaves with a small heavy trowel over a clean plastic surface. In Australia, a standard
'barbeque tray' designed to hold food at out-of-door parties has been found to be particularly
convenient. Visual inspection of leaves can be successful in discovering the presence of thrips,
but is more dependent on operator efficiency, and is less likely to be effective at relatively low
population levels than a simple and careful beating method.
The range of plant species on which this thrips may potentially be found is very great and not
possible to predict. It appears to be particularly associated with species of Araceae that are
cultivated in the domestic environment for their attractive leaves (Collins, 1998). However, it
also develops populations on many other plants, including Capsicum crops and various weeds
(Vierbergen, 1998), and has now been recorded from members of almost 30 different plant
families
When identifying this pest the following data should be recorded:
a. The name of the thrips
b. Reference number of the sample identified
c. Scientific name of the associated host plant
d. Country of origin of the material, including all relevant subsequent transportation details, such
as movement of material from ship or aircraft to site where the thrips were found
e. Report of any associated damage symptoms
f. Photomicrograph of specimen for comparison with those provided here
g. Depository of voucher specimens
h. Identity of identifier
Symptom Description
This thrips feeds on leaf tissue and the damage is very similar to typical mite damage with light
spots on the leaf. It will feed on both the upper and lower leaf surfaces but is usually more
common on the lower surface. Their numerous but shallow punctures result in injured tissue with
a shrunken appearance, and the light colour is a result of the cell constituents, including
chlorophyll, being removed. Infested leaves will have numerous black specs on them that are
fecal droppings of the thrips. They also will feed on parts of the flower.
Sites of Infection/Infestation
Mainly a pest of the foliage, but when population levels increase it may invade flowers.
Identification
Handling/Preservation
Techniques for preparing micro-slides of thrips
A - SLIDE PREPARATION FOR ROUTINE IDENTIFICATIONS
The following method, using a water-soluble mountant, such as Hoyers or CMC10 (from
Masters Co. Inc. 890 Lively Blvd. Wood Dale, IL 60191, (630) 238-9292,
[email protected]). This method is rapid and thus relatively inexpensive.
1. Remove the specimens from the collecting fluid into clean 70% alcohol and attempt to open
the wings and straighten the antennae using micro-pins (see below).
2. Place a drop of Hoyers Mountant or CMC10 Mountant onto a cover slip (13mm circle, No. 1).
Place a thrips into this drop, ventral side uppermost, and gently lower a slide onto the drop.
Invert the slide as soon as the mountant has spread sufficiently.
3. Place immediately into an oven, or onto a hot-plate, at about 40-50°C. Leave for a few hours
before attempting to study. Alternatively warm over a spirit lamp.
4. When the mountant is dry, ring with nail varnish and label appropriately (see below).
B - SLIDE PREPARATION FOR ARCHIVING AND TAXONOMIC STUDY
To reveal fine details of body sculpture and minute setae, specimens need to be macerated
gently. A few specimens may be prepared without maceration to preserve the natural
colouration.
TOOLS
Specimens can be manipulated with fine micro-pins, mounted in sealing wax on match sticks. A
simple lifting tool can be made from a small loop of fine wire. The best dishes are 'excavated
glass blocks', 15mm high, 40mm square with an excavation of about 5ml volume.
MACERATION
Maceration removes body contents by soaking specimens in a weak NaOH solution. Treatment
overnight in about 2% solution seems optimum, but black specimens require longer (even several
days). Maceration of thrips should always be carried out at room temperature, in contrast to
techniques used for preparation of aphid and coccid specimens.
1. Place thrips into clean water in an excavated block; it is best if the specimens float with their
wings on the surface. Leave for 1 hour.
2. Add to the water an equal volume of 5% NaOH solution and leave overnight.
3. Transfer the specimens from NaOH solution to water for a few hours, using a needle or wire
loop. Then transfer the specimens into 60% ethanol for storage or further treatment.
4. Replace the 60% alcohol with 70% alcohol and leave for about 1 hour.
5. Replace with 80% alcohol and leave for 20 minutes.
6. Replace with 95% alcohol and leave for 10 minutes.
7. Replace with absolute alcohol and leave for 5 minutes.
8. Replace with fresh absolute alcohol and leave for another 5 minutes.
9. Transfer to clove oil and leave until fully clear.
MOUNTING
Prepare a small mounting block by fixing to the centre of a microscope slide a 2 mm deep layer
of 25 mm square card, and cover this with plastic tape to provide a clean, surface.
1. Place a clean 13 mm diameter cover slip onto the mounting block; put a drop of Canada
Balsam onto the centre of the cover slip and into this place one thrips specimen ventral side
uppermost.
2. Spread the legs and wings, and straighten the antennae by pressing on the basal segments with
a fine needle.
3. Invert a clean microscope slide and lower it firmly but gently onto the specimen in balsam on
the cover slip. As soon as the surfaces touch, re-invert the slide with the coverslip adhering.
Sometimes it helps to place a small drop of balsam in
the centre of the slide before touching the balsam on the cover slip.
4. Place the slide onto a hot-plate at once, at about 50°C, to drive off the xylene as quickly as
possible. Dry the slides in an oven at about 50°C.
LABELLING:
With the head of the thrips directed toward you, the right hand label should indicate the host
plant, followed by the country (in capital letters) and then the locality and date, with collector's
name (and code number). The left hand label should indicate the sex, morph and genus and
species names of the thrips.
Morphological Methods
Adults of Echinothrips are particularly easy to recognize and distinguish from other thrips by
their appearance and structure. With experience and a hand lens, they can be recognized from
their general appearance, including the dark brown body with red internal pigment, the slender
antennae with at least two segments largely yellow, the unusually slender forewings that have
transverse light and dark bands and bear conspicuously long setae, and the bicoloured legs with
brown femora and extensively yellow tibiae (Fig. 1).
Figure 1. Echinothrips americanus, habitus.
These characters contrast with those of the Greenhouse Thrips, Heliothrips haemorrhoidalis, the
only species in Australia with which Echinothrips might be confused. That species also has the
head and pronotum reticulate, but has no red internal pigment, yellow legs, and paler forewings
(Fig. 2).
Figure 2. Heliothrips haemorrhoidalis, habitus.
However, as with all Thysanoptera, for precise identification at species level it is essential to
prepare specimens onto microscope slides (see Specimen Handling and Preservation), and to
examine these with a compound (preferably phase-contrast) microscope. Slide-mounted voucher
specimens should be kept for future reference.
Adults
Membership of the genus Echinothrips can be established unequivocally by the possession of the
first three of the following character states; the fourth occurs in six of the species but not in the
one that lives on Selaginella in Costa Rica: the fifth character state also occurs in a few unrelated
species of Thripidae.
1. Head and pronotum conspicuously reticulate (Fig. 3)
Figure 3. Echinothrips americanus, head and prothorax.
2. Mesothoracic internal furca with a prominent median spinula (Fig. 4)
Figure 4. Echinothrips americanus, mesa- and meta-thoracic furcae.
3. Forewing costal and first longitudinal veins both with continuous series of setae that are longer
than the wing width and have capitate apices, but second longitudinal vein with no setae (Figs 5,
6).
Figure 5. Echinothrips americanus, wing.
Figure 6. Echinothrips americanus, wing setae.
4. Pronotum posterior margin with two pairs of setae longer than second antennal segment (Fig.
3)
5. Males have an array of more than 50 small circular glandular areas on the abdominal sternites
(Fig. 7).
Figure 7. Echinothrips americanus, male sternites V-VIII.
Figure 8. Echinothrips americanus, male sternites IV-VI
An identification key to the seven known species of Echinothrips is available in Mound &
Marrulo (1996). Four of these seven species are highly distinctive, but are considered not likely
to enter into quarantine considerations:
Echinothrips subflavus Hood can be distinguished from the other members of the genus by its
yellow body colour, because the other six species are all brown. This species lives on the needles
of Tsuga in eastern North America.
Echinothrips asperatus Hood and E. pinnatus Hood are both known only from single female
specimens collected in southern Brazil. These differ from other all other members of the genus in
having distinctively broad, fringed apices to the major setae on the head, pronotum and
forewings.
Echinothrips selaginellae Mound is known only from Costa Rica, living on one species of
Selaginella, and is distinguished by the acutely pointed major setae on the forewing, and the lack
of long setae on the pronotum.
The other three species in the genus are all polyphagous with extensive distributions in the
Americas. The character states in the published literature on which these three have been
distinguished may not be entirely reliable, because of variation that occurs within and between
populations in such widely distributed species. This variation has never been examined
thoroughly in these three Echinothrips species, and needs to be based on large samples
throughout the range of each of them, between north-eastern U.S.A., Central America and the
Caribbean, and South America, including Brazil. It is possible that an irregular cline may exist
across this vast area, and that the named forms are merely variants along this cline. This
possibility is of economic importance because the quantity of living plants exported from Central
and South American countries is steadily increasing, and some of these may be infested with
these thrips.
1. Echinothrips americanus is distinguished from E. caribbeanus Hood and E. mexicanus
Moulton by the presence of sculpture lines within most of the reticles on the head and pronotum
(Fig. 3). In contrast, markings within the sculptured reticles are considered to be completely
absent in the latter two species. However, the extent of these marking varies within available
populations of E. americanus, such that some individuals within a population have many fewer
such markings than other individuals.
2. Echinothrips americanus has distinctive long microtrichia on the lines of sculpture on the
lateral areas of the abdominal tergites (Fig. 8). Microtrichia like these are absent from the tergites
of E. mexicanus, but they are present in E. caribbeanus although in smaller numbers than in E.
americanus.
3. Echinothrips americanus has a pair of setae on the second antennal segment of which the
apices are slightly expanded. In contrast, these setae have acute apices in the other two species.
This difference is, however, usually too weak and too subjective for critical distinction between
these species except where it is strongly developed.
Larvae
The immature stages are not known for six of the species of Echinothrips, but the larvae of E.
americanus are readily distinguished from those of other species of Thripidae by the following
combination of character states.
1. Colour largely yellow with red eyes (Fig. 9)
2. Dorsal surface with no obvious sculpture (Fig. 10)
3. Abdominal tergites each with three pairs of long, weakly fringed setae (Fig. 10)
4. Head with three pairs of long, weakly fringed setae (Fig. 9)
Figure 9. Echinothrips americanus larva
Figure 10. Echinothrips americanus larval setae
Further Information
Contacts
The only fully comprehensive collection of the known species of Echinothrips belongs to the
United States Museum of Natural History, Washington, whose collections of Thysanoptera are in
the care of the United States Department of Agriculture, Beltsville, Maryland.
The Natural History Museum, London, and the Senckenberg Museum, Frankfurt also hold
collections of several species in this genus.
The pest species itself is well known to workers in several countries, including USA (Florida,
Georgia, California), Australia (Canberra), and in Europe, England (York) and Netherlands
(Wageningen).
Contact addresses for Thysanoptera collections and specialists
1. United States National Museum of Natural History, PO Box 37012, Smithsonian Institute,
Washington D.C., 20013-7012 U.S.A.
2. The Natural History Museum, Cromwell Road, London SW7 5BD, England.
3. Senckenberg Forschungsinstitut und Naturmuseum, Senckenberganlage 25, 60325 Frankfurt,
Germany.
4. Dr Mark Hoddle, Department of Entomology, University of California, Riverside, CA 92521,
U.S.A.
5. Dr Stan Diffie, Department of Entomology, University of Georgia, P.O. Box 748, Tifton, GA
31793 U.S.A.
6. Dr Dom Collins, Pest and Disease Identification Team, Central Science Laboratory, Sand
Hutton, York YO41 1LZ, England.
7. G. Vierbergen, Plant Protection Service, Section of Entomology, P.O. Box 9102, 6700 HC
Wageningen, The Netherlands
8. Dr Laurence Mound, CSIRO Entomology, GPO Box 1700, Canberra, ACT 2601.
Acknowledgements
The information displayed on these Poinsettia Thrips webpages was sourced from the Diagnostic
Protocol for Echinothrips americanus the Poinsettia Thrips (Mound, L (2008)) and the
Echinothrips americanus Pest Risk Review. These documents were kindly provided by Plant
Health Australia.
References
Andreas Kahrer, and Christa Lethmayer 2000. Echinothrips americanus MORGAN
(Thysanoptera, Thripidae) introduced into Austria (original language German).
Pflanzenschutzberichte 59 (1), p. 47. Abstract: Echinothrips americanus (Thysanoptera,
Thripidae) is reported herewith for the first time from Austria. It was found in Vienna in a
greenhouse living an azalea (Rhododendron simsii) in February 2000, where it caused heavy
damage.
Collins, D.W. 1998. Recent interceptions of Echinothrips americanus Morgan (Thysanoptera,
Thripidae) imported into England. Entomologist's Monthly Magazine 134: 1-4.
Marullo,R and A. Pollini 1999. Echinothrips americanus, a new pest of Italian greenhouses
(original language Italian). Informatore Fitopatologico 49 (6), 61-64 (1999)
Morgan, A.C. 1913. New genera and species of Thysanoptera, with notes on distribution and
food plants. Proceedings of the U.S. Natural Museum 46: 1-55.
Mound, L.A. & Marullo, R. 1996. The Thrips of Central and South America: An Introduction.
Memoirs on Entomology, International 6: 1-488.
Oetting, R.D. & Beshear, R.J. 1994. Biology of the greenhouse pest Echinothrips americanus
Morgan (Thysanoptera: Thripidae). Zoology (Journal of Pure and Applied Zoology) 4: 307-315.
van Schelt, J., Hoogerbrugge, H., van Houten, Y. & Bolckmans, K. 2002. Biological control and
survival of Echinothrips americanus in pepper. In: Integrated Control in Protected crops,
Temperate Climate. IOBC/wprs Bulletin 25 (1): 285-288.
Vierbergen, G. 1998. Echinothrips americanus Morgan, a new thrips in Dutch greenhouses
(Thysanoptera: Thripidae). Proceedings of the section Experimental and Applied Entomology of
the Netherlands Entomological Society (N.E.V.)
9: 155-160.
Vierbergen, G. 2001. Occurrence of glasshouse Thysanoptera in the open in the Netherlands.
Proceedings of the 7th International Symposium on Thysanoptera. pp. 359-362.
Vierbergen, G., Cean, M., Szeller, I.H., Jenser, G., Masten, T. & Simala, M. 2006. Spread of two
thrips pests in Europe: Echinothrips americanus and Microcephalothrips abdominalis
(Thysanoptera: Thripidae). Acta Phytopathologica et Entomologica Hungarica 41: 287-296.
Websites:
http://ipm.ncsu.edu/AG136/thrips4.html;
http://www.entomology.umn.edu/cues/inter/inmine/Thripf.html;
http://www.denverplants.com/foliage/html/Thrip.htm.