Proc. Indian Acad. Sci., Vol. 86 B, No. 6, December 1977, pp. 405--408, © Printed in India.

A note on oviposition in the maeropterous and braehypterous forms of the rice brown planthopper, Nilaparvata lugens Stal (Homoptera, Delphacidae)

T M MANJUNATH University of Agricultural Sciences, Regional Research Station, V C Farm, Mandya 571405

MS received 28 July 1977

Abstract. The pre-ovipostion period, oviposition period, longevity and fecundity of the macropterous and brachypterous females of the rice brown planthopper, Nila- parvata lugens Stal, averaged 2.9 and 3.0 days; 8'4 and 9"2 days; 10.5 and 16.5 days; and 421 "8 and 485"8, respectively. The egg-laying habit of this pest is described and its daily rate of oviposition illustrated.

Keywords. Brown planthopper; macropterous form; brachypterous form; oviposition.

1. Introduction

The dee brown planthopper, Nilaparvata lugens Stal (Homoptera, Delphacidae), has assumed importance as a serious pest of paddy in recent years. Some informa- tion on the biology of this pest has been given by Mochida (1964) and Bae and Pathak (1970). This paper records some interesting observations on the oviposition, fecun- dity and longevity of the macropterous (winged) and brachypterous (with ill-de- veloped wings) forms of the brown planthopper.

2. Materials and methods

A pure culture of N. lugens was built up in the laboratory from field collections made at Holalu (Mandya) during May/June 1976. For conducting the following studies about 100 late instar nymphs were removed from the general cage and reared indi- vidually in glass vials; on becoming adults, the macropterous and brachypterous forms were separately released into cylindrical jars containing paddy stems in the ratio of I female : 2 males and left for a day to ensure mating. As sufficient bra- chypterous males could not be obtained at a time, only macropterous males were used in either case. The next day one male and one female were coupled and left in a 6" × 1" glass vial, providing a fresh paddy stem (about 30-day-old) cut at about 5" height for oviposition. The root region was washed and wrapped with a thin layer of wet cotton to keep the stem turgid and also to provide humidity. Perio- dical observations were made on the oviposition habit. The stem was examined after 24 hr under a binocular microscope and the number of egg masses and the

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406 T M Manjunath

number of eggs laid in each mass were counted. Fresh stem was provided daily for oviposition until the female died. The dead female was dissected under a bino- cular microscope and the number of ovarian eggs counted. The data on daily rate of oviposition and fecundity were thus obtained. Observations were also made on the pre-oviposition period and longevity. Ten macropterous and ten brachypterous females were thus studied during the experiments.

The temperature and humidity during the period of studies were: Range Average

Maximum temperature 25.6-30.6 ° C 28.6 ° C Minimum temperature 23.3-26-1 ° C 24-8 ° C Relative humidity 62.0-84.0 % 73.6 %

3. Results

The egg-laying commenced most frequently on the 3rd day of adult emergence (range 2-4 days).

The eggs were thrusted into the leaf sheath covering the base of the plant or some- times into midrib of the leaf on the ventral side. They were laid in longitudinal rows and in such a way that only the opercular region is visible from outside.

Most oviposition occurred at morning. Before laying each egg, the female inserted its ovipositor into the tissue and moved it up-and-down to lacerate the tissue until an incision or pocket of the required depth is formed. Such up-and-down move- ment varied from 8 to 47 (av. 23 for 50 observations), lasting 23-62 seconds (av. 34 , seconds). As the eggs were laid, the female moved backward and downward.

The average length of the egg was 0.9 nun and width 0.15 mm (widest at about the middle of the egg). It is elongate with the anterior end slightly tapering and curved. The operculum is roundish. The chorion is smooth, creamish and translucent when laid, but turns brownish after 3 days. The pink eye spots also develop by the 3rd day.

The egg incubation period ranged from 6 to 8 (av. 6.5) days, the most frequent day of hatching being on the 6th day.

The particulars of the oviposition period, fecundity and longevity of the macro- pterous and brachypterous forms are given in table 1. The daily rate of oviposition is illustrated in figure 1.

It can be seen from the table that the oviposition period averaged 8.4 (range 5-11) days in the macropterous form and 9.2 (range 7-14) days in the brachypterous form. The fecundity of the macropterous female ranged from 305 to 574 (av. 421.8) while that of the brachypterous female ranged from 374 to 667 (av. 485.8). Thus, the brachypterous form is more fecund than the macropterous form. Over 10 ~o of the total eggs produced were found retained in the dead females. The greatest number of eggs were laid during the first eight days of oviposition and as the female aged, the number of eggs laid decreased. The largest number of eggs laid by a macro- and brachypterous female in a day was 85 and 100, respectively (figure 2). The number of eggs per mass varied from 2 to 90, the average being 13.4 for 604 egg masses con- sisting of 8,074 eggs. Oviposition normally ceased three (range 2 to 5) days before death.

Longevity of the macropterous and brachypterous females ranged from 11 to 17

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Figure 1. Average daily rate of oviposition by macropterous and brachypterous forms of Nilaparvata lugens (av. of lO mated females each. Vertical lines indicat¢ the maximum and minimum no. of eggs laid on each day).

Figure 2. A leaf tissue dissected to expose the eggs of the rice brown planthopper.

(av. 14.6) days and 13 to 21 (av. 16.5) days, respectively, while that of the male was 6 to 15 (av. 10.5) days.

Eggs hatched mostly in the morning. The first instar nymphs usually moved on to the leaves for feeding, but the later instars preferred the basal part of the plant.

408 T M Manjunath

Table 1. Pre-oviposition period, oviposition period, fecundity and longevity of Nilaparvata lugens at 24.8 -- 28.6°C and 73.6 % R.H.

No. of Pre-ovi- Ovi-posi- No. of eggs observa- position tion Retain-

period period Laid (in masses) ed in tions (days) (days) ovary

Longevity (days) Total Females Males

Macropterous form

1 3 9 497 (38) 58 555 16 11 2 3 8 540 (46) 9 549 15 9 3 3 I1 315 (24) 72 387 17 11 4 2 8 346 (28) 61 407 14 13 5 3 9 291 (29) 55 346 16 12 6 4 5 264(19) 52 316 12 6 7 3 9 363 (36) 15 378 15 9 8 2 7 279 (25) 26 305 11 7 9 3 10 562 (34) 12 574 16 15

10 3 8 339 (28) 62 401 14 12

Range 2-4 5-11 264-562 (I9-46) 9-72 305 - 574 11-17 6-15 Mean 2.9 8.4 379.6 (30.7) 42.2 421"8 14.6 10.5

Brachypterous form

1 3 14 585 (37) 82 667 21 2 4 7 350 (25) 61 411 15 3 3 I1 444 (34) 52 496 17 4 3 7 426 (30) 43 469 14 5 3 9 358 (26) 16 374 17 6 4 9 582 (41) 56 638 18 7 2 8 273 (18) 142 415 15 8 3 8 411 (29) 38 449 15 9 2 8 377 (31) 55 432 13

10 3 11 472 (26) 35 507 19

Range 2-4 7-14 273-582 (18-41) 16-142 374-667 13-21 Mean 3 9.2 427-8 (29.7) 58.0 485"8 16"5

They normally completed their development on a single tiller and there was very little migration during the nymphal stage. There were five nymphal instars, each lasting 3-4 days. The moulted skin of the I to V instars measured from tip to tip 0.757, 0.893, 1-304, 1.609 and 2-000 ram, respectively (av. of 10 individuals of each instar).

Acknowledgements

The author is grateful to K C Devraj Urs, for his encouragement and to Gavi Gowda for help in these studies.

References

Bae S H and Pathak M D 1970 Life history of Ntlaparvata lugens (Homoptera: Delphacidae) and susceptibility of rice varieties to its attacks; Ann. Entomol. Soc. Amer. 63 149-155

Mochida O 1964 On oviposition in the brown planthopper, Nilaparvata lugens (Stal) (Homoptera, Anchenorrhyncha). 1. Oviposition and environmental factors with special reference to tempera- ture and rice plant; Bull. Kyushu dgric. Expt. Sta. 10 257-285