Species accounts

Western flower thrips

Frankliniella occidentalis

FAMILY

Thripidae

TAXONOMY

Euthrips occidentalis Pergande, 1895, California, United States.

FEEDING ECOLOGY AND DIET

Feeds on pollen, also flower and young leaf tissues; sometimes predatory on mites.

REPRODUCTIVE BIOLOGY

Usually bisexual, but males develop from eggs that have not been fertilized.

CONSERVATION STATUS

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

About 0.04 in (1 mm) long; color yellow to dark brown.

DISTRIBUTION

Throughout temperate parts of the world, but originally western United States.

HABITAT

Flowers and leaves of many plants.

BEHAVIOR

Individuals commonly fly for hundreds of yards when their host plant is disturbed, but long-distance transport is due to the horticultural trade in plants. Males sometimes compete for territories on a leaf, but only when the population density is low.

Not threatened; a serious pest that requires control throughout much of the world.

SIGNIFICANCE TO HUMANS

This is one of the most important horticultural pests in the world, causing serious damage to flower crops, tomatoes, capsicums and cucumbers, as well as stone fruits and table grapes. As well as direct feeding damage, the thrips infects many plants with viruses.

Ectoparasitic thrips

Aulacothrips dictyotus

FAMILY

Heterothripidae

TAXONOMY

Aulacothrips dictyotus Hood, 1952, Brazil.

Order: Thysanoptera

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

About 0.06 in (1.5 mm) long; dark brown, with third and fourth antennal segments larger than remaining seven segments and both bearing a greatly elongate, convoluted sensory area.

DISTRIBUTION

Southern Brazil.

HABITAT

Under the wings on the upper surface of the abdomen of a plant-feeding treehopper, Aetalion, (Aetalionidae) unlike the flower-feeding habit of all other Heterothripidae.

BEHAVIOR

The host insect lives in colonies, thus making it easier for the larval thrips to transfer between individuals when these molt. The bugs become disturbed when the adult thrips walk over them.

FEEDING ECOLOGY AND DIET

All life stages, from the youngest larvae to pupae and adults, live under the wings of the host insect, presumably sucking its blood.

REPRODUCTIVE BIOLOGY

Possibly parthenogenetic; the male is not known. Eggs have not been observed, but newly emerged first instar larvae occur on the abdomen of their host, together with later instar larvae and pupae. Each pupa is enclosed in a transparent cocoon fixed to the surface of the host’s abdomen.

CONSERVATION STATUS

Not listed by the IUCN, although currently reported from only two localities.

SIGNIFICANCE TO HUMANS

None known.

Crowned thrips

Ecacanthothrips tibialis

FAMILY

Phlaeothripidae

TAXONOMY

Idolothrips tibialis Ashmead, 1905, Philippines.

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

About 0.08–0.16 in (2–4 mm) long; third antennal segment bears crown of at least 10 large sensoria, (most of the 3,500 members of the family have only one to three small sensoria on this segment). Front legs or large males are greatly enlarged and bear a stout tooth on the tarsus; smallest males and females have slender front legs. The last abdominal segment is tubular (as in all Phlaeothripidae); forewings do not have veins bearing setae.

DISTRIBUTION

Old World tropics, from Africa to northern Australia.

Vol. 3: Insects

Ecacanthothrips tibialis

Oncothrips waterhousei

Cycadothrips albrechti

HABITAT

On dead twigs and branches.

BEHAVIOR

Males exhibit great variation in size and are known to be subsocial or even truly social. Males fight other males to defend either a single female or a single egg mass to which several females will progressively contribute. Smallest males may attempt to sneak mate while their larger siblings are fighting. Small males have a nutritional advantage in that they require less food to achieve maturity; thus there is a balance between feeding and mating advantages.

FEEDING ECOLOGY AND DIET

Adults and larvae feed on fungal hyphae growing on freshly dead wood.

REPRODUCTIVE BIOLOGY

Eggs are laid on the surface of dead twigs among the fungus on which adults and larvae feed.

CONSERVATION STATUS

Not listed by the IUCN.

SIGNIFICANCE TO HUMANS

None known.

Australian acacia gall thrips

Oncothrips waterhousei

FAMILY

Phlaeothripidae

TAXONOMY

Oncothrips waterhousei Mound and Crespi, 1995, Australia.

OTHER COMMON NAMES

None known.

Vol. 3: Insects

PHYSICAL CHARACTERISTICS

Winged and wingless morphs of both sexes are about 0.06 in (1.5 mm) long. Wingless adults mainly yellow, with thorax and forelegs enlarged, antennae short. Winged adults are dark brown with slender forelegs and thorax, long slender antennae.

DISTRIBUTION

Widespread across the arid zone of Australia.

HABITAT

Gall-inducing on the phyllodes (leaves) of several Acacia species.

BEHAVIOR

Wingless adults of both sexes function as soldiers to defend their gall from invading kleptoparasitic thrips and also moth larvae.

FEEDING ECOLOGY AND DIET

When a female feeds on a young phyllode, this is induced to form a small pouch that rapidly encloses the insect.

REPRODUCTIVE BIOLOGY

Female lays eggs within the hollow gall soon after becoming enclosed. These hatch, and larvae of this first small generation develop into wingless soldiers. A second generation is then produced in which the adults are fully winged and disperse to found new galls.

CONSERVATION STATUS

Not listed by the IUCN. Presumably threatened by progressive destruction by farmers of host plants to feed livestock, particularly during years of drought.

SIGNIFICANCE TO HUMANS

None known.

Australian cycad thrips

Cycadothrips albrechti

FAMILY

Aeolothripidae

TAXONOMY

Cycadothrips albrechti Mound and Terry, 2001, Australia.

Order: Thysanoptera

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

About 0.08 in (2 mm) long, color varies from golden yellow to light brown. Forewings are broad, as in other members of the family, but third antennal segment bears two unusually inflated sensoria. Large males have pair of stout, thornlike setae near tip of abdomen; these setae scarcely developed in small males.

DISTRIBUTION

Central Australia, near Alice Springs.

HABITAT

Breeds in the male cones of the cycad Macrozamia macdonnellii.

BEHAVIOR

Breeds in a particularly hot and arid area, has only been seen to fly late in the afternoon when the humidity rises. At that time, both sexes fly in swarms from the male cones on which they have fed and produced larvae, and each adult carries about 20 pollen grains on its body. Concurrently, a powerful odor is given off by any mature female cone, and this attracts the flying thrips, and induces them to crawl inside with their pollen load.

FEEDING ECOLOGY AND DIET

Adults and larvae suck the contents from the pollen grains of M. macdonnellii; populations have been estimated at 50,000 adults in a single cone.

REPRODUCTIVE BIOLOGY

Variation in size of males and the powerful setae near the tip of their abdomen suggests some sort of male competitive behavior in mating, but this has not been observed. Larvae develop only in male cones, and subsequently fall to the ground to pupate around the base of the cycad.

CONSERVATION STATUS

Not listed by the IUCN. The only known pollinator of this species of cycad, a plant that grows only in a restricted area of central Australia. In their mutual adaptation, the future existence of both is threatened by human activity.

SIGNIFICANCE TO HUMANS

None known.

Resources

Books

Crespi, B. J., and L. A. Mound. “Ecology and Evolution of Social Behaviour Among Australian Gall Thrips and Their Allies.” In Evolution of Social Behaviour in Insects and Arachnids, edited by J. Choe and B. J. Crespi. Cambridge, UK: Cambridge University Press, 1997.

Lewis, T., ed. Thrips as Crop Pests. Wallingford, UK: CAB International, 1997.

Mound, L. A. “Thysanoptera.” In Zoological Catalogue of Australia. Vol. 26, Psocoptera, Phthiraptera, Thysanoptera, edited by A. Wells. Melbourne: CSIRO Publishing, 1996.

Periodicals

Izzo, T. J., S. M. J. Pinent, and L. A. Mound. “Aulacothrips dictyotus (Heterothripidae), the First Ectoparasitic Thrips (Thysanoptera).” Florida Entomologist 85 (2002): 281–283.

Mound, L. A., and R. Marullo. “The Thrips of Central and South America: An Introduction.” Memoirs on Entomology, International 6 (1996): 1–488.

Mound, L. A., and I. Terry. “Pollination of the Central Australian Cycad, Macrozamia macdonnellii, by a New Species of Basal Clade Thrips (Thysanoptera).” International Journal of Plant Sciences 162 (2001): 147–154.

Other

Moritz, G., D. C. Morris, and Mound, L. A. “ThripsID: Pest

Thrips of the World.” CD-ROM. Melbourne: CSIRO

Publishing, 2001.

Laurence A. Mound, DSc