J. Bioi. Control, 13: 33-38, 1999

Biology and life table of Rhynocoris Inarginatas (Fabricius) (: ) on three lepidopteran pests

P. J. EDWARD GEORGE Entomology Research Unit St. Xavier's College, Palayamkottai 627002, Tamil Nadu, India

ABSTRACT: Fecundity and adult longevity of both the sexes in Rhynocoris marginatus (Fabricius) were maximal while total developmental period was minimal when this reduviid predator was reared on larvae ofSpodoptera litura (Fabricius) in place ofEarias villella (Boisduval) or Corcyrcl cephalonica (Stainton). Its intrinsic rate of increase and net reproductive potential were of the highest order if the predator always fed on caterpillars of S. lituTa.

KEY WORDS: Corcyra cephalonica, Earias vittella, life table, predator, prey influence, Rhynocoris marginatus, Spodoptera litura

Several of reduviids prey upon influences the growth rate, survival (O'Neil a wide range of of various and Wiedenmann, 1990; Ambrose and sizes, holding promise as useful agents in Rani, 1991), reproductive potential and life biological control of crop pests. table characteristics of the predator Rhynocoris marginatus (Fabricius) is one determining the population build-up of the such predator of various economically latter. Acquisition of such knowledge important insect pests such as Corcyra enables adoption of steps for augmenting cephalonica (Stainton) (Bhatnager et at.. predator population for release in the field 1983), cingulatus (Fabricius), as a biocontrol agent in an insect pest Earias insulana (Boisduval), Spodoptera management programme. It is from this litura (Fabricius) (Sahayaraj, 1994). standpoint that the present investigation has Anomis flava (Fabricius), Achaea janata been undertaken and the information (Linnaeus), Helicoverpa armigera incorporated in this paper examine these (Hubner) (Prabakar, 1994) and Mylabris issues with respect toR. marginatusreared pustulata (Thunberg) (Ambrose et al., on S. litura, E. vittella or C. cephalonica. 1996). It is known that food value EDWARD GEORGE

MATERIALS AND METHODS base of natural logarithms, 'x' is the age of the individuals in days, Ix is the number of The adults of R. marginatus were individuals alive at age 'x' as the proportion collected from Kumbakkarai scrub jungle of 1, and 'm ' is the number of female x (l DON, 78°E), Madurai district of Tamil offsprings produced per female in the age

Nadu and reared in the laboratory interval 'x'. The sum of products '1 xm x ' is separately on mature fourth instar larvae the net reproductive rate (R). The rate of of Spodoptera litura, Earias vittella or multiplication of population for each Corcyra cephalonica in plastic containers generation was measured in terms of (6cm diam, 6cm ht) covered on the top by females produced per generation. The plastic lids with holes for aeration. A precise value of cohort generation was cohort consisting of 100 eggs of the calculated as follows. predator from each such reared set was

used to construct life tables. These eggs 2:.1 xm x

were allowed to hatch in small plastic vials T=----c

(4 cm diam, 4 cm ht) in which moistened R o cotton swabs were kept for maintaining optimum humidity (85%). The cotton The arbitrary value of innate capacity

swabs were changed periodically to prevent for increase 'r'c was calculated from the fungal attack. After noting egg hatchability, equation: all the newly hatched nymphs were reared individually in another set of plastic vials of similar dimensions. Fourth instar larvae r c = of S. litura, E. vittella or C. cephalonica T c were provided as prey for the respective cohort. Observations were made on This is an appropriate 'rrn' value. The nymphal duration, adult emergence, their values of negati ve exponent of e-rrnx total developmental time, age specific ascertained from this experi ment often lay mortality, adult longevity and egg output outside the range. For this reason both of mated females in their lifetime. sides of the equation were multiplied by a 7 Differences in biological parameters for the factor of Ee -rm x 1 x m x - 1096.6 (Birch, 7 -r three prey species were analysed by one 1954). The two values ofu m x I x m x were way ANOVA (SAS Institute, 1988) and then plotted on the horizontal axis against Tukey test (Tukey, 1953). their respective arbitrary 'rrn ' on the vertical axis. Two points were then joined to give Life tables were constructed according a line, which was intersected by a vertical to the methods described by Birch (1954) line drawn from the desired value of and elaborated by Southwood (1978). In 7 e -r m xl x m x -1096.6. life table statistics the intrinsic rate of increase was determined by using the The point of intersection gives the value J equation l:e mXlxmx -1. Where 'e' is the of 'rm' accurate to three decimal places.

34 Biology and life table of R. marginatus

The precise generation time (T) was then RESULTS AND DISCUSSION calculated from equation: Egg incubation period and total developmental duration were shortest T=----- and adult longevity of both sexes was

r m maximal when individuals were reared on larvae of S. litura instead of on The finite rate of increase (A.) caterpillars of E. vittella or C. cephalonica was calculated as erm. The weekly (Table I). Fecundity per female was also multiplication of predator population was highest if this predator preyed on larvae of calculated as (ermr. The doubling time was S. litura. calculated as log21l0gA..

Table 1. Biological data of R. marginatus reared on three insect pests (x ± SD)

Prey species Parameter S. litura E. vittella C. cephalonica

Incubation period 9.00 ± oa 9.75 ± 0.72h 9.90± 0.471> Nymphal duration

I instar 9.25 ± 0.44- 9.45 ± 0.51' 10.25 ± 0.641>

II instar 8.25 ± 0.79' 8.74 ± 0.45h 9.06± 0.80" III instar 9.75 ± 0.64" 10.50 ± 0.62h 11.6 ± 1.15" IV instar 11.82 ± 0.52" 13.69 ± 0.48h 16.13 ± 0.52" V instar 22.50 ± 0.78" 24.79 ± 0.70·1> 26.47 ± 0.52b Total developmental period 70.38 ± 2.22" 76.93 ± 2.09h 83.47 ± 2.67"

Longevity 79.87 ± 12.13a 68.47 ± 12.49b 65.29 ± 11.04b Pre -oviposition period 20.43 ± 2.84" 23.42 ± 3.14b 28.75 ± 3.77"

Fecundity 191.89 ± 39.69" 151.44 ± 30.69h 121.75 ± 25.15c

Meaps followed by the same alphabet in a row are not statistically significant by Tukey test (P> 0.05).

35 EDWARD GEORGE

The life table parameters of consequence of better nutrition obtained R. marginatus in relation to three prey by the predator with minimum expenditure insects are given in Table 2. Highest of energy during predation. Similar Table 2 Population growth of R. marginatus reared on three prey species Prey species Parameter S. litura E. vittella C. cephalonica

Gross reproductive rate (GRR) 96.00 75.00 60.00

Net reproductive rate (R) 65.95 41.35 27.90

Mean length of generation (T) 100.34 112.15 110.82 Innate capacity for increase in numbers (r) 0.042 0.033 0.031

Corrected (rill) 0.048 0.039 0.035

Corrected generation time (T) 87.27 95.44 95.10

Finite rate of increase in numbers 1.049 1.040 1.035

Weekly multiplication rate (WMR) 1.399 1.314 1.278

Doubling lime (DT) 14.49 17.67 20.15

Hypothetical females in F 2 generation 4349.40 1709.82 778.41 survival and maximum female progency observations were made by Anderson were noted when reared on caterpillars of (1962) on Anthocoris spp., Venkatesan S. iitura. The net reproductive rate (R ) o et aI. (1997) on a Cydnocoris giIvus was significantly higher if the prey was (Burm.) and George et aI. (1998) on larvae of S. iitura instead of E. vittella or Acanthaspis siva (Distant). C. cephalonica. The intrinsic rate of population increase of R. marginatus was The highest fecundity of females and maximal in respect of S. litura larvae maximum longevity of adults of both sexes wherein the mean length of generation and following rearing of this reduviid species popUlation doubling time were also on larvae of S. litura noted in this shortest. Further, the weekly multiplication investigation also seem to be a refle~tion rate of the predator raised on this prey was fastest. of the superior nutritional quality of such prey diet (George, 1999). This conclusion The shortest total developmental concurs with the influence drawn by period recorded in R. marginatus when Venkatesan et al. (1997) and George et al. reared on S. litura might be the (1998). They also observed high egg

36 Biology and life table of R. marginatus

output and maximum longevity in reduviids response of Rhynocoris marginatus C. gilvus and A. siva reared on S. litura. Fab. (Heteroptera: Reduviidae) to Mylabris pustulata Thunb (Coleoptera: In the present study, larvae of S. litura Meloidae). Fresenius Environmental as pr~y of R. marginatus was found to Bulletin, 5: 85 - 89. favour faster development, longer survival, greater egg output, higher net reproductive Anderson, N. H. 1962. Growth and rate and shorter population doubling time fecundity of Anthocoris spp. reared on of the predator. It suggests that, in various prey (Heteroptera: biocontrol programmes, predators using Anthocoridae). Entomology considerable attention is needed to select Experimental & Applied. 5: 40 - 52. the appropriate prey species for population build-up of predators. Bhatnagar, V. S., Sithanantham, S. S., Pawar, C. S., Jadav, D., Rao, V. R. and Reed, W. 1983. Conservation and ACKNOWLEDGEMENTS augmentation of natural enemies with I wish to express my gratitude to Rev. reference to integrated pest Fr. Antony A. Poppuraj, S. J., Principal, management in chickpea (Cicer St. Xavier's College (Autonomous), arietinum L.) and pigeonpea (Cajanus cajan L.) Millsp. Proceedings of Palayarnkottai for the facilities. My sincere International Workshop on [PM for thanks to Dr. Dunston P. Ambrose, grain legumes, Goiani, Brazil, pp.157- Director, Entomology Research Unit, St. 180. Xavier's College (Autonomous) for the continued encouragement and DST New Birch, S. 1954. The intrinsic rate of natural Delhi for financial assistance under Young increase in an insect population. Scientist Scheme (HR I OY I Z - 07 197). Journal of Ecology, 17: 15 - 26. REFERENCES George, P. J. E., Seenivasagan, R. and Ambrose, D. P. and Rani, M. R. S. 1991. Kannan, S. 1998. Influence of prey Prey influence on the laboratory mass species on the development and rearing ofRhynocoris kumarii Ambrose reproduction of Acanthaspis siva and Livingstone, a potential biological Distant (Heteroptera: Reduviidae). control agent (Insecta: Heteroptera: Entomon, 23 (4): 69- 75. Reduviidae). Journal of Mitterand George, P. J. E. 1999. Nutritional influence Zoological Museum Berlin, 67 (2): 339 of prey on the biology and biochemistry - 349. in a harpactorine reduviid Sycanus Ambrose, D. P., Claver, M. A. and collaris Fabricius. Journal of Insect Mariappan, P. 1996. Functional Science (In press).

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0' Neil, R. J. and Wiedenmann, R. N. SAS Institute, 1988. SAS/STAT Users 1990. Body weight of Podisus guide, release 6.03 edition. SAS maculiventris (Say) under various Institute Incorporation, Cary. feeding regimes. Canadian Entomology, 122: 285 - 294. Southwood, T. R. E. 1978. Ecological methods: With particular reference to Prabakar, V. 1994. Impact of prey the study of insect population. deprivation on the predatory behaviour Chapman and Hall, London. of R. marginatus Fab. (Insecta: Heteroptera: Reduviidae) on Tukey, J. W. 1953. The problem of mUltiple Helicoverpa armigera (Hub.). M. Phil. comparisons. Princeton University. thesis, M. S. University, Tirunelveli, 28 Princeton, N. J. pp. Venkatesan, S., Seenivasagan, R. and Sahayaraj, K. 1994. Biocontrol potential Karuppasamy, G. 1997. Influence of _, evaluation of the reduviid predator prey species on feeding response, R. marginatus Fab. to the groundnut development and reproduction of the pest Spodoptera litura (Fab.) by reduviid Cydnocoris gilvus Burm. functional response study. Fresenius (Reduviidae, Heteroptera). Entomon, Environmental Bulletin, 3: 546 - 556. 22 (1): 22 - 27.

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