Understanding why animals choose one food over another is one of the key questions underlying the fields of behaviour ecology. This study aims to test if ladybird beetle, Propylea dissecta Mulsant (Coleoptera: Coccinellidae) can forage selectively for nutrients in order to redress specific nutritional imbalances to maximise their fitness. We hypothesised that the presence of more food choices leads to bad decisions in terms of their food selection which ultimately negatively affects the mating and reproductive parameters of P. dissecta. To test this, we first manipulated the predator's nutritional status by rearing them in five separate dietary groups from first instar larvae to newly emerged adult stage. Thereafter, we tested their food choice between five different foods, i.e. Aphis craccivora Koch, Aphis nerii Boyer de Fonsclombe, conspecific eggs, heterospecific eggs and mixed pollen grains, equidistantly placed in a Petri dish. Based on the food choice of the newly emerged adults, they were reared on the chosen diet for 10 days. Thereafter, adults were paired with their opposite sex (collected from stock culture reared on A. craccivora) and mating and reproductive parameters were recorded. Our results suggested that the variety of food did not affect the food choice of ladybird beetle, P. dissecta. They tend to choose their natural diet, i.e. aphid in each dietary regime. We found that previous dietary regime, i.e. larval dietary regime, significantly influences the mating and reproductive parameters of both the male and female except for the time to commence mating by the male. Food choices of adult beetles were found to significantly influence the time to commence mating, average fecundity and per cent egg viability in males and only mating duration in females. Our findings suggest that P. dissecta consistently made optimal decisions when facing various food choices. They consistently preferred their natural and preferred food choice over others, indicating a strong food selection behaviour.

Food preferences and choices are common among animals, including insects. Studies on food preferences have been done on coccinellids using eggs and aphids as diet, but information on the food choices of the aphidophagous ladybird, Propylea dissecta (Coleoptera: Coccinellidae), under laboratory conditions, is scarce. This study examined the effect of physical activity (walking) on food choice. We reared P. dissecta larvae on aphids, Aphis craccivora (Hemiptera: Aphididae), until the fourth-instar stage, and then allowed the fourth-instar larvae to walk on a glass rod for different time intervals to illustrate the energetic costs of foraging. After walking, larvae were provided simultaneous food choices of equidistantly placed food, i.e., A. craccivora, conspecific eggs, and heterospecific eggs. As the walking time duration gradually increased, the level of larval activity increased, resulting in poorer food choices.

Intraspecific variation is the variation in morphology, physiology, behaviour, and social organisation of any species as it adapts to changing environmental circumstances by varying its feeding habits. In the present study, we investigated the disparities between the preselected (F1) and postselected (F15) populations of Propylea dissecta Mulsant (Coleoptera: Coccinellidae) when fed on four different prey species, namely Aphis gossypii Glover from bottle gourd, Lagenaria vulgaris Seringe (Cucurbitaceae), Lipaphis erysimi (Kaltenbach) from mustard, Brassica campestris Linnaeus (Brassicaceae), Rhopalosiphum maidis (Fitch) from maize, Zea mays Linnaeus (Poaceae), and Uroleucon compositae (Theobald) from chrysanthemum, Chrysanthemum indicum Linnaeus (Asteraceae), under an experimental evolution study. A simple bimodal pattern of distribution was obtained for each prey species, which was warped with variations in prey species for both F1 and F15. This research might provide the basis for further studies on the differential pace of development of various other prey species, improve understanding of ecological evolution, and provide a spectrum of fast-growing bioagents for the introduction of biological control strategy in pest management techniques against agropests.

The effects of selection on developmental variants have not yet been rigorously investigated on variable prey quantities. We investigated the food exploitation strategy of first (F1) and fifteenth (F15) generation slow and fast developers of Propylea dissecta (Mulsant) in the presence of scarce and abundant quantities of pea aphid, Acyrthosiphon pisum (Harris), and its effect on adult body mass and reproductive attributes. Both selected slow developers and selected fast developers were higher in number than their counter unselected generation on scarce and abundant diets, respectively. Immature survivals of selected slow developers were depressed after the selection process while it was enhanced for selected fast developers on both diet regimes. On both diets, the total developmental duration was longer for selected slow developers and shorter for selected fast developers. Fecundity and percent egg viability were greater in selected fast developers with plentiful prey supply and lower in control slow developers with inadequate prey supply. More adult body mass was found for pre-selected slow developers than selected slow developers on a scarce diet but selected fast developers enhanced their body weight than unselected individuals of fast developers on an abundant diet. The present experimental evolution findings point to the presence and persistence of developmental variations with variability in their developmental and reproductive traits on allocating scarce and abundant prey supplies.

In the present study, we assessed functional response curves of two generalist coccinellid beetles (Coleoptera: Coccinellidae), specifically Menochilus sexmaculatus and Propylea dissecta, using fluctuating densities of aphid prey as a stimulus. In what may be the first such study, we investigated how the prey density experienced during the early larval development of these two predatory beetle species shaped the functional response curves of the late instar–larval and adult stages. The predators were switched from their rearing prey-density environments of scarce, optimal, or abundant prey to five testing density environments of extremely scarce, scarce, suboptimal, optimal, or abundant prey. The individuals of M. sexmaculatus that were reared on either scarce- and optimal- or abundant-prey densities exhibited type II functional response curves as both larvae and adults. However, individuals of P. dissecta that were reared on scarce- and abundant-prey densities displayed modified type II functional response curves as larvae and type II functional response curves as adults. In contrast, individuals of P. dissecta reared on the optimal-prey density displayed type II functional response curves as larvae and modified type II functional response curves as adults. The fourth-instar larvae and adult females of M. sexmaculatus and P. dissecta also exhibited highest prey consumption (T/Th) and shortest prey-handling time (Th) on the scarce-prey rearing density. Thus, under fluctuating-prey conditions, M. sexmaculatus is a better biological control agent of aphids than P. dissecta is.

Food availability is a fundamental factor determining an animal's potential fitness. Carry-over effects of food limitation from development to adulthood are known to influence reproduction, ageing, and tolerance to stress. We have examined the effect of stage-specific variation (before adult emergence or pre-emergence, post-emergence and post-mating) in food availability in Propylea dissecta (Mulsant). Larvae were reared separately on two different pre-emergence food regimes (abundant or restricted) until pupation. Newly emerged adults were further split into two groups and placed on abundant or restricted post-emergence regimes. After mating, females were split and reared on any one of two post-mating regimes. The results revealed that: (i) time to commence mating declined with increased food availability in pre- and post-emergence stages, (ii) mating duration increased with food availability post-emergence, (iii) highest reproduction output was observed in individuals who had abundant food pre- and post-emergence. However, food availability at the time of oviposition also had a strong influence on fecundity. Solo bouts of scarcity, regardless of which stage suffered them, were effectively managed in at least two of the three stages (pre-emergence, post-emergence, post-mating) had abundant food.

Operational sex ratio and paternal age are known to independently affect mating behaviour and reproductive performance. We conducted experiments to assess the effects of operational sex ratio and paternal age on mating, reproduction, and total development duration of Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae). Three male-biased sex ratios, no (1:1), modest (1:2), and extreme (1:5) competition treatments, were formed using young, middle-aged, and old males. The reproductive performance of M. sexmaculatus at all ages under extreme competition (1:5) surpassed the other two treatments. More competition among males decreased the time of commencement of mating and increased the duration of copulation. Females laid a greater number of eggs in extreme competition treatments. The operational sex ratio (irrespective of age) had no significant effect on the total developmental duration of offspring. Among different age groups, older males took more time to commence mating and mated for longer durations in all the sex ratio treatments. The number of eggs in the first clutch was lowest when females were mated with older males with increased offspring development duration. Thus, it can be concluded that male-biased sex ratio elevates the performance of M. sexmaculatus. Among different age groups, older males were poor performers than young and middle-aged males.

Under natural conditions, prey resources may fluctuate considerably in space and time; and predators are continuously faced with challenges of resource availability and use. In this study, effects of fluctuations (scarce/optimal/abundant) in biomass of pea aphid (Acyrthosiphon pisum (Harris); Hemiptera: Aphididae) during rearing and experimental conditions on certain predatory attributes (consumption rate/conversion, efficiency/growth rate) of two sympatric aphidophagous Coccinellidae (Coleoptera) were evaluated. Results revealed significant influence of rearing conditions on conversion efficiency and growth rate; and experimental conditions on all three predation attributes of Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae). Larvae/adults of M. sexmaculatus had similar consumption rates per rearing condition, but exhibited highest and lowest consumption rates when abruptly shifted to abundant and scarce prey experimental conditions. Further, scarce prey reared larvae/adults of M. sexmaculatus displayed highest conversion efficiency and growth rate on optimal/abundant prey experimental condition(s). However, all three predation attributes of larvae/adults of Propylea dissecta (Mulsant) (Coleoptera: Coccinellidae) were influenced substantially by both the rearing and experimental conditions; and scarce prey reared larvae/adults exhibited highest predation attributes on optimal/abundant prey experimental condition(s). Moreover, predation attributes of M. sexmaculatus were higher than P. dissecta on the three experimental conditions. Therefore, this study suggests that M. sexmaculatus has a better compensatory ability to overcome prey resource fluctuation than P. dissecta.

The emitted aliphatic hydrocarbon profile of four Indian Coccinellidae (Coleoptera), Coccinella septempunctata (Linnaeus) (C7), Coccinella transversalis Fabricius (Ct), Menochilus sexmaculatus (Fabricius) (Ms), and Propylea dissecta (Mulsant) (Pd) has been investigated by simple solvent-less headspace solid-phase microextraction (HS-SPME) technique coupled with gas chromatography and mass spectroscopy (GC-MS). Identified volatile and non-volatile compounds were confirmed by running corresponding standards and comparing with the National Institute of Standards and Technology library. Among the 56 identified aliphatic hydrocarbons, saturated aliphatic hydrocarbons were more in number than unsaturated ones. Among saturated hydrocarbons, methyl branched hydrocarbons were more in number in C7 and Ct than Ms and Pd. Menochilus sexmaculatus and Pd had higher percentages of unsaturated hydrocarbons than C7 and Ct. Among branched chain-hydrocarbons, mono-methylated saturated hydrocarbons were more in number than dimethylated saturated hydrocarbons. Further analysis of the semiochemical profile revealed a closeness between C7 and Ct, and between Ms and Pd. Quantitative analysis revealed that straight chain hydrocarbons form separate clusters to branched chain methylated hydrocarbons. This is the first attempt to identify the semiochemical profile of some Indian coccinellids using the headspace solid phase micro-extraction technique coupled with the gas chromatography-mass spectrometry technique. This report will be helpful for various chemotaxonomic studies of the species in the future.

Multiple interactions occurring within aphidophagous guilds determine their final predation outcomes, i.e., antagonistic, additive, or synergistic. Based on these predatory outcomes, the suitability of guilds in suppressing aphid pests is determined. The present study assesses the efficacy of 11 guilds, formed from both larval and adult stages of four locally abundant aphidophagous coccinellids (Coleoptera: Coccinellidae), while exploiting the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae). The observed antagonistic effects within these guilds are resultants of enhanced predator–predator interactions due to the size and diversity of guild predators. Smaller ladybird predators maintained their usual body mass, probably by increasing their conversion efficiencies to compensate for their reduced prey consumption. However, larger ladybirds reported loss in their body mass, owing to their higher energy needs. The overall guild conversion efficiencies and growth rates were reduced. Among the experimental guilds, the observed prey mortalities were relatively higher in two-predator guilds, and within these two-predator combinations, the higher prey mortalities were recorded in those guilds where Coccinella septempunctata was one of the predators.

In the present study, we aimed to assess the suitability of predatory parameters, namely voracity, consumption index, conversion efficiency and growth rate, as measures of prey suitability. For this purpose, fourth-instar larvae and 10-day-old adult females of four co-occurring ladybirds, namely Coccinella septempunctata (L.) (C7), C. transversalis F., Cheilomenes sexmaculata (F.) and Propylea dissecta (Mulsant), fed on two essential species of aphid prey, Aphis craccivora Koch and Lipaphis erysimi (Kaltenbach), were observed. The results revealed that, with the exception of C7, the other three ladybirds performed better on A. craccivora. Previous studies based on reproductive and developmental attributes have also shown that A. craccivora is a more suitable prey for these three ladybirds, indicating a strong correlation and affirming the viability of using these measures as a mark of prey suitability. In a similar manner, fourth instars and adult females of C7 performed better on L. erysimi over A. craccivora. This detectable difference in consumption and utilization of aphid prey species by the four ladybirds indicates that these predatory parameters can be used as tools for assessing prey suitability in ladybirds.

Male contributions, both chemical and behavioural, can influence female sperm usage and reproductive success. To determine whether such male factors are subject to depletion in Coccinella septempunctata and Coccinella transversalis, we tested the effects of male mating history on male virility, as estimated by measures of mating behaviour, female reproductive success and progeny fitness, with parental age held constant. Overt measures of male mating effort (wriggling duration, number of shaking bouts and total copula duration) all diminished from virgin to 5 × mated males and were mirrored by concurrent declines in female fecundity and fertility (measured over 20 days). Paternal effects were also observed which diminished as a function of mating history, suggesting that transgenerational signals of male origin are also subject to depletion. Progeny of virgin fathers had higher rates of survival (C. transversalis) and faster development (both species) than progeny of 5 × mated fathers. Seminal fluid proteins are known to have allohormonal properties and can stimulate female fecundity and fertility in a number of insects, making them strong candidates for depletion as a function of mating activity. However, it is also possible that sperm limitation and/or reduced tactile stimulation of females by multiple-mated males may have contributed to some of the observed effects.

The influence of solitary versus group rearing on the development and survival of the three-striped ladybird beetle Brumoides suturalis (Fabricius) was studied using two aphid species, Acyrthosiphon pisum (Harris) and Aphis gossypii Glover, as diet. Rearing pattern (solitary or group) had no significant influence on the success of rearing, but prey species did. While immature stages developed faster on A. pisum, the survival of early instars was higher on A. gossypii. Diet had no effect on pupal survival.

The ovipositional orientation of an aphidophagous ladybird beetle, Propylea dissecta (Mulsant) (Coleoptera: Coccinellidae) in terms of geo- and photo-taxis, colour and texture of substrates was studied. The beetle exhibited a high preference for negatively geotactic substrates for oviposition. There was no clear preference for positively or negatively phototactic substrates. When studied in combination, it was observed that substrates that were negatively geotactic were preferred over other substrates regardless of the phototaxis. Red was highly preferred over the other 5 colours tested, and plastic was the substrate of choice for P. dissecta oviposition.