Biological Control 34 (2005) 187–195 www.elsevier.com/locate/ybcon Preference–performance of a generalist predatory ladybird: A laboratory study Omkar *, Geetanjali Mishra Ladybird Research Laboratory, Department of Zoology, University of Lucknow, Lucknow 226 007, India Received 2 February 2005; accepted 18 May 2005 Abstract The fitness consequences of feeding on different aphids, viz. Aphis craccivora, Aphis gossypii, Aphis nerii, Lipaphis erysimi, Myzus persicae, Rhopalosiphum maidis, and Uroleucon compositae (Homoptera: Aphididae), for the life stages of a generalist predatory ladybird, Propylea dissecta (Coleoptera: Coccinellidae) were measured in the laboratory in terms of their preference (prey biomass consumed and oviposition site selection), performance (development, survival, reproduction, mortality and fertility life tables, and individual fitness levels of predator), and preference–performance correlations. The study revealed that P. dissecta consumed A. craccivora the most and deposited more eggs on plants infested with this aphid species. The performance levels of predator varied significantly between aphid species with best performance on A. craccivora and worst on A. nerii. High performance on A. craccivora was contradictory to most literature and can be attributed to host plant dependent prey suitability. P. dissecta seems to be a gen- eralist aphidophagous ladybird as it readily developed and reproduced on all seven aphid species. We correlated a composite per- formance measure (individual fitness) to two estimates of preference (biomass of prey consumed and oviposition site selection). Positive preference–performance correlations suggest that preferential prey consumption and selection of a host plant–prey complex as an oviposition site are an indicator of ladybird performance. Ó 2005 Elsevier Inc. All rights reserved. Keywords: Propylea dissecta; Coccinellidae; Feeding specialization; Ladybird; Preference; Performance; Preference–performance correlation 1. Introduction nies is an indicator of essential or nursery (prey pre- ferred by immature stages) prey. It was on further Food associations of ladybirds (Coleoptera: Cocci- extension of the above concept that the classifications nellidae) have been put under detailed scrutiny because of prey based on survival, development, and reproduc- of their economic value as biocontrol agents. Earlier, tion of predator, cost of capture, and toxin content were the presence of a ladybird in prey vicinity was sufficient brought forward, and are the largely accepted means of to warrant its inclusion in prey range of predator (Bal- identifying prey range (Hodek, 1959, 1962; Hodek and duf, 1935; Schilder and Schilder, 1928). Thompson Honek, 1996; Malcolm, 1992). The presence of a hierar- (1951), however, challenged this view and stated that chy among different prey and specialization for certain identification of prey range needs to be based on more prey has been proved for a number of ladybird species concrete proofs, such as the life attributes on a particu- (Blackman, 1965, 1967; Kalushkov, 1994, 1998; Mills, lar prey. Mills (1981) suggested that the presence of 1981; Olszak, 1986; Omkar and Bind, 2004; Omkar ladybird larvae, particularly later instars, in prey colo- and James, 2004; Omkar and Srivastava, 2003; Pervez and Omkar, 2004a). The costs and benefits of prey specialization have recently been studied and have * Corresponding author. indicated increasingly better performance of the preda- E-mail address: [email protected] (Omkar). tor on a poor aphid when reared continuously over six 1049-9644/$ - see front matter Ó 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.biocontrol.2005.05.007 188 Omkar, G. Mishra / Biological Control 34 (2005) 187–195 generations (Rana et al., 2002). Another study however Lucknow, India, and kept at 25 ± 2 °C, 65 ± 5% RH discussed the impact of mixed diets on life attributes of and 14L:10D on a mono-specific aphid supply in Petri predator and the better performance on them owing to dishes (9.0 · 2.0 cm). The following aphid–host plant innate dietary self-selection (Soares et al., 2004). complexes were chosen for their local availability: A. Prey suitability and preference are subjected to a craccivora Koch from bean (Dolichos lablab Linnaeus), number of factors, such as host plant constituents, plant A. gossypii Glover from bottle gourd (Lagenaria vulgaris architecture, and seasons (Clark and Messina, 1998; Seringe), Aphis nerii Boyer de Fonsclombe from milk- Geitzenauer and Bernays, 1996; Hukusima and Kamei, weed (Calotropis procera (Aiton)), Lipaphis erysimi 1970; Krebs and McCleery, 1994; Okamoto, 1966; Voh- (Kaltenbach) from mustard (Brassica campestris Lin- land, 1996). The foraging behaviour of adult females naeus), M. persicae from black nightshade (Solanum ni- among available food types, i.e., preference, and the grum Linnaeus), Rhopalosiphum maidis (Fitch) from subsequent development, survival, and reproduction, sorghum (Sorghum bicolor (Linnaeus)), and Uroleucon i.e. performance, are important determinants of prey compositae (Theobald) from safflower (Carthamus suitability (Tauber and Tauber, 1987). Preference and tinctorius Linnaeus). The field-collected adults were sup- performance correlations have largely been studied in plied exclusively with either one of the aphids for one herbivorous insects (as reviewed by Thompson, 1988; generation and the resultant F1 adults were used in the Via, 1986) but very few in predaceous ones (Sadeghi, experiments. Fresh aphids were provided ad libitum 2002; Sadeghi and Gilbert, 2000). every 24 h. Propylea dissecta (Mulsant) (Coleoptera: Coccinelli- Rearing of adults and their progeny for a genera- dae) is a polymorphic, Oriental ladybird commonly tion on an exclusive aphid supply prior to being used found in the agricultural fields infested with Aphis gos- in experiments was done to acclimatise them to the sypii and A. craccivora (Pervez and Omkar, 2004a). It prey, and avoid loss of fitness of future generations has earlier been reported from aphids, Aphis affinis del from a sudden switch from one nutrient source to Guercio and Myzus persicae (Sulzer) (Singh and Bali, another (field prey to laboratory prey) as indicated 1993), and coconut caterpillar Opsinia arenosella Walker by Rana et al. (2002). All experiments were conducted (Pillai and Nair, 1986). Though the growth, develop- under abiotic conditions similar to that of the stock ment, and reproduction of its pale morph on seven aphid culture. species have been studied (Pervez and Omkar, 2004a), that of the typical morph has not yet been studied. Fur- thermore, no a priori studies on its preference–perfor- 3. Experimental design mance correlations exist. Fitness consequences of seven aphid species commonly occurring in the local habitat 3.1. Preference of P. dissecta on its various life attributes, viz. develop- ment, reproduction, fertility and mortality life tables, 3.1.1. Prey biomass consumption and individual fitness levels are thus being assessed here. A 24 h starved adult female (10-day-old) was provid- The study reported here has three aims. First, we aim ed with 100 aphids of either one of the seven aphids on to identify the preference of typical morph of P. dissecta respective host plant twig in a muslin-covered beaker for host plant–aphid complexes present commonly in its (9.5 cm · 6.5 cm) for 3 h after which the unconsumed local habitat by studying the biomass of prey consumed aphids were counted. The experiment was conducted and oviposition site selection. Second, we aim to assess in 10 replicates for each of the seven aphids. the performance of the ladybird by comparing the fit- Second instars of the larger sized aphids, A. craccivo- ness consequences (intrinsic suitability) of the different ra and A. nerii, and third instar of smaller sized aphids, aphid species as food for its larvae and adults under lab- viz. A. gossypii, L. erysimi, M. persicae, R. maidis, and oratory conditions, testing the null hypothesis that all U. compositae, were selected to standardise size of prey aphids are equally good as food for the larvae. Third, across the seven different prey types. The second and we test the existence of a preference–performance corre- third instar stages were selected to ensure intermediate lation in P. dissecta, i.e., whether preference is indicative size for maximum prey biomass utilisation and con- of the performance of this ladybird on a prey. sumption (Roger et al., 2000). The biomass consump- tion was evaluated by weighing 100 aphids of each species (instars as provided in experiment) using elec- 2. Materials and methods tronic balance (SARTORIUS-H51, Westbury, New York, USA) from which average biomass of prey con- 2.1. Laboratory maintenance sumed by each individual was calculated and the data were subjected to one-way ANOVA followed by post A laboratory culture of P. dissecta was established hoc TukeyÕs test of comparison using MINITAB from adults captured in the fields adjoining the city of (2003) on PC. Omkar, G. Mishra / Biological Control 34 (2005) 187–195 189 3.1.2. Oviposition site selection transformed using arcsine square root transformation The ovipositional behaviour of P. dissecta was evalu- prior to being subjected to ANOVA. All data were test- ated on seven host plant–aphid combinations under ed for normality using BartlettÕs test (SAS, 2002). choice conditions to decipher its preference for oviposi- tion site. The experiment was conducted in a rectangular 3.2.2. Mortality life table glass chamber (70 · 50 · 3 cm), which was divided For the construction of mortality life table, the fol- equally into 8 chambers (17.5 · 25 · 3 cm). One of the lowing parameters, viz. x is the age interval at which corner chambers was sealed off using thermocol to pre- sample was taken, i.e., eggs, the four larval instars, pre- vent entry of ladybirds or aphids into it. All the borders pupae, pupae, and adults in the present study; Sx is the of the remaining seven chambers were lined with 1 in. survival rate of a stage, calculated as number of individ- double adhesive tape and a host plant–aphid combina- uals surviving stage x/number of individuals in xÀ1 tion placed in the centre of each one of the chambers.