Helionothrips errans (Williams, 1916)

Panchaetothripinae, Thripidae, Terebrantia, Thysanoptera

Figures

Fig. 1: 8-segmented antenna, segments III and IV with forked sense cone, terminal segments VI-VIII
Fig. 2: Head dorsal with ocellar triangle
Fig. 3: Head and pronotum
Fig. 4: Meso- and metanotum
Fig. 5: Meso- and metasternum with lyre-shaped furca
Fig. 6: Meso- and metasternum plates
Fig. 7: Fore- and hind wing, fore wing distal region
Fig. 8: Tergites III-VI
Fig. 9: Tergite VIII with posteromarginal comb and tergite IX
Fig. 10: Sternite VII and base of ovipositor valves

Helionothrips errans occurs on the leaves of orchids. Female macropterous; body dark brown; head yellow anterior of fore ocellus; tarsi and apical third of mid and hind tibiae yellow; antennal segments I, II & VI brown, VII & VIII grey brown, III-V pale yellow; fore wing brown, with white transverse band sub-basally and diffuse paler area sub-apically. Antennae 8-segmented; segments III and IV with long apical neck and long forked sense cone, VIII about five times as long as VII (Fig. 1). Head with short, convex cheeks; occipital ridge strong and close to posterior margin of eyes; reticulation strong in front of occipital ridge but weak on posterior collar (Fig. 2). Pronotum reticulate, with semicircular hind margin and no long setae (Fig. 3). Metanotum with triangular area of strong sculpture, bearing 1 pair of widely spaced setae but no campaniform sensilla (Fig. 4); metafurca lyre-shaped (Fig. 5 and 6). Mid and hind tarsi 1-segmented. Fore wing first vein close to or fused to costal vein; second vein with 6 or 7 setae; first vein with 6 setae at base and 2 distally; costal cilia longer than costal setae, posteromarginal cilia wavy (Fig. 7). Tergites III-VII with distinctive sculpture on antecostal ridge forming a series of about 5 arches (Fig. 8); VIII with comb of long trichoid teeth, usually medially incomplete (Fig. 9); X with median split complete. Sternites II-VII with 3 pairs of long centrally located setae (Fig. 10).
Male similar to female; sternites VII & VIII each with a small circular glandular area near anterior margin; tergite IX with 2 pairs of spine-like setae and a group of about 6-10 small tubercles on posterior half of tergite.

The genus Helionothrips Bagnall, 1932
This genus includes 27 described species, mostly from the Asian region, but with 3 from Africa, one from Australia, and one from South America that is possibly not congeneric (Mound & Marullo 1996). Members of Helionothrips have distinctive tergal sculpture forming a series of arches on the antecostal ridges of each abdominal segment, the head has a transverse ridge dorsally, and the sense cone on antennal segments III & IV is forked. It is possible that the character states used to distinguish between members of Helionothrips are subject to more inter-population variation than the keys given by Wilson (1975).

Compared to other Panchaetothripini, Helionothrips errans has a distinctive tergal sculpture forming a series of horseshoe-like arches on the antecostal ridges of each abdominal segment. The genus is apparently most closely related to Hercinothrips, but differs in having 1-segmented tarsi, a distinct sculptured triangle medially on the metanotum, and the anterior vein of fore wing only with a few scattered setae (Hercinothrips with 2-segmented tarsi, without dominant sculptured median triangle on the metanotum, and fore wing first vein setal row almost complete). Compared to other Panchaetothripinae with a distinct occipital ridge dorsally on head, only in Helionothrips errans and Panchaetothrips noxius the occipital collar is in contrast to the rest of the head weakly sculptured (in Xestothrips glabratus there is no difference between surface sculpture of occipital collar and the rest of the head; in Monilothrips kempi the occipital collar is in contrast to the rest of head heavy reticulate sculptured).

Life history
Eggs are laid in the orchid leaves by the adult female. After about a week, an immature (or nymph) emerges and starts feeding on the leaf surface. The nymphs go through four stages before becoming adults, with all stages feeding on the orchid leaf tissues. It is likely under optimal conditions such as glass house that the entire life cycle can be completed in about a month (Gillespie 2008).

Host plants
Crops: cassava, coffee, karela (bitter melon), onion, orchids (Dendrobium, Laelia).
Weeds: Galinsoga parviflora, Solanum incanum.

Vector capacity
None identified, but possible mechanical distribution of phytopathogenic fungi and bacteria.

Damage and symptoms
The feeding damage results from these pests sucking the cell contents from the epidermal and underlying cells of the orchid leaf giving initially a ‘silvered’ look to the leaf but this quickly browns and dies off, possibly causing leaf fall of extensively damaged plants (Gillespie 2008).

Detection and control strategies
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Biogeography

Recorded widely in greenhouses of temperate regions (USA and Europe) and in the tropics (Taiwan and Africa). Kenya, Uganda.

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