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Description and Bionomics of Frankliniella insularis Franklin (Thysanoptera)

Published online by Cambridge University Press:  10 July 2009

J. Davidson  and
J. G. Bald
J. Davidson
Affiliation:
Waite Agricultural Research Institute, University of Adelaide
J. G. Bald
Affiliation:
Division of Economic Botany, Commonwealth Council for Scientific and Industrial Research.
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Extract

(1) Frankliniella insularis (Franklin) is found on various food-plants, including tomatos, in the Adelaide area.

(2) The life-history and bionomics of the species have been investigated, particularly on tomato plants under glasshouse conditions. The various stages of the insect have been described.

(3) The eggs are laid in the tissues of the tomato leaf, and the larvae feed on the leaves or in the flowers; when mature they leave the plants and pupate in the débris on the surface of the soil or penetrate into the upper layers of the soil. Sometimes they pupate on the plant in rolled leaves, depressions in the stem or other similar situations; this habit has been also observed on tomato plants growing in the open during the summer. In carnation flowers eggs were laid in the tissues of the sepals and petals.

(4) The duration of the egg stage for 64 examples varied from 9–14 days when the mean daily temperature was 64·5° F. In a number of other observations it was found to vary from 3 days, when the mean temperature was 100° F., to 15 days, when the mean temperature was 63·1°F. The rate of oviposition is markedly affected by temperature: with a mean temperature of 77·5° F., one female laid an average of 3·9 eggs daily; two other females laid an average of 1·2 and 1·7 eggs daily when the mean temperature was 68·2°F.; and another female laid an average of 1·3 eggs when the mean temperature was 67·7° F. Below 60° F. the rate of oviposition is greatly retarded, but egg-laying may extend over a long period: one female continued oviposition over a period of 157 days. The largest number of eggs laid by a single female was 92 over a period of 70 days.

(5) The duration of the larval stages for 32 individuals varied from 9 to 13 days when the mean temperature of the periods varied from 66·6° F. to 65·7° F. In a number of observations on other individuals at various times the period varied from 7 to 14 days when the mean temperature varied from 74·9° F. to 63·4° F.

(6) The duration of the pupal stages obtained from 19 individuals varied from 7 to 14 days when the mean temperature of the periods varied from 72·8° F. to 66·7° F.

(7) The complete life-cycle under glasshouse conditions occupied 36–39 days when the mean temperature of the period was about 66° F. Observations made on a number of individuals at various periods gave a variation in the period of the complete life-cycle from 13 to 41 days with mean temperatures varying from 89·5° F. to 64·1° F.

(8) The chief distribution of Frankliniella insularis appears to be the region of Central America. It is common in the Adelaide area during the warmer period of the year (approximately November to April), and rare or absent during the remaining months. Its seasonal occurrence appears to be due to temperature, since it was readily reared at all periods of the year on tomato plants in the glasshouse.

(9) The economic importance of the species is due to the fact that G. Samuel and J. G. Bald have shown experimentally that it can transmit the virus of spotted wilt disease of tomatos.

Type
Original Articles
Information
Bulletin of Entomological Research , Volume 21 , Issue 3 , October 1930 , pp. 365 - 385
Copyright
Copyright © Cambridge University Press 1930

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References

* Specimens of this species of thrips were taken in carnation flowers and on tomato plants in the Adelaide area by G. Samuel in November and December 1927. The material was submitted to the Imperial Bureau of Entomology for determination, and the species was identified as Frankliniella insularis by G. D. Morrison, who stated that this was the first record for the species from Australia.

† The thrips were reared on leaves of tomato plants either in spring-clip tubes or in small glass lamp-globes. The spring-clip tubes were 9 mm. internal diameter and were supported on wire stakes by spring clips in a convenient position. One end of the tube rested on the leaf surface, the latter being pressed up to the mouth of the tube from below by a cork and rubber stopper attached to a spring; the other end of the tube was plugged with cottonwool. In this way the insects at various stages were restricted to the small area of leaf enclosed by the end of the tube; single individuals were readily isolated in this way. With the breeding globes, a leaf of a young tomato plant was inserted into the globe, the petiole being surrounded with a plug of cottonwool. The other end of the globe was plugged with cottonwool. The insects in various stages were reared on the leaf inside the globe. Complete details of this technique will be found in the Bulletin referred to above.

* These temperatures were obtained from daily readings of a maximum and minimum thermometer hanging on the wall of the glasshouse 3 ft. above the bench. The records from a thermograph placed on the bench were found to give on an average a daily mean temperature about 5° F. lower than the maximum and minimum thermometer hanging above the bench. It is possible that the actual temperature experienced by the insects was somewhat lower than registered by this thermometer.

In fig. 2 the mean temperature is shown for two periods calculated from the thermograph records and plotted as average mean daily temperature for three-day periods. The temperatures referred to in the paper are taken from readings of max. and min. thermometer in the glasshouse except where stated otherwise.

* During the summer period larvae of Frankliniella insularis were found pupating in dried rolled leaves and in crevices between the calyx and the fruit on tomato plants in the open, so that the cottonwool plugs afforded a suitable medium. This latter habit has been observed by Russell in his investigations with Heliothrips fasciatus, Pergande (U.S. Dept. Agric. Bur. Entom. Bull. 118, Oct. 1912).

* This would mean that the critical cold point for the species is about 53° F., which seems high. If the actual temperatures experienced by the insects were 5° F. lower than recorded, as explained on page 369, a shift of 5° to the left would place the critical cold point at about 48° F.