Avanish K. Gupta

Reproductive performance of four aphidophagous ladybirds on cowpea aphid, Aphis craccivora Koch

Abstract:  This study investigated prey consumption, egg production, percent progeny loss, reproductive, pre‐ and post‐reproductive periods, reproductive time ratio, reproductive rate and bioconversion efficiency of four aphidophagous ladybirds, viz. Cheilomenes sexmaculata (Fabricius), Coccinella septempunctata Linnaeus, Coccinella transversalis Fabricius and Propylea dissecta (Mulsant) on Dolichos lablab Linnaeus infested with cowpea aphid, Aphis craccivora Koch. C. sexmaculata had the highest bioconversion efficiency, reproductive rate and reproductive time ratio followed in rank order by P. dissecta, C. transversalis and C. septempunctata. This study indicates that C. sexmaculata has a narrow ecological relationship with A. craccivora. The increased allocation of resources to reproduction as indicated through a high reproductive time ratio and high bioconversion efficiency of C. sexmaculata and P. dissecta suggest that they may be better adapted to compete for this prey with larger species like C. transversalis and C. septempunctata.

Intrinsic advantages of Cheilomenes sexmaculata over two coexisting Coccinella species (Coleoptera: Coccinellidae)

Abstract Development, survival and reproductive performance of coexisting ladybird species, viz. Cheilomenes sexmaculata, Coccinella septempunctata, and Coccinella transversalis, of the tribe Coccinellini were studied and compared to assess their coexistence and ecological relationships. High values of life history parameters, viz. developmental rate, immature survival, fecundity, egg viability, reproductive rate and conversion of efficiency of ingested food were recorded for C. sexmaculata followed by C. transversalis and C. septempunctata suggesting that the former has intrinsic advantages over the latter two species. This could possibly counterbalance its disadvantages, like relatively smaller size and weight, thereby making it competitive. The developmental period increased with increase in body size. Exceptionally high fecundity after single mating has been recorded in C. sexmaculata. The egg viability, however, was lower than in both Coccinella species.

Why do neonates of aphidophagous ladybird beetles preferentially consume conspecific eggs in presence of aphids

Abstract The neonates of aphidophagous ladybird beetles, Propylea dissecta, Coccinella transversalis and Coelophora saucia preferentially consumed conspecific eggs in presence of essential aphid prey, Aphis gossypii. This preference was strongest in P. dissecta and recorded in all density combinations of conspecific eggs and aphids. The neonates of all three species developed faster resulting in heavier second instars with lower mortality when fed on conspecific eggs as compared to mobile or defenceless aphids. In addition, they required less dry biomass of conspecific eggs than that of aphids. These results reveal that neonates are benefitted intrinsically when they feed on conspecific eggs. The neonates of P. dissecta exhibited discrimination for more nutritious food, as they contacted and ate conspecific eggs more frequently than aphids as their first meal. This discrimination was not found in Coccinella transversalis and Coelophora saucia possibly due to their bigger sizes and possible higher energy requirements. Although, the major effect of chemical cues was only noticed in P. dissecta, it could be concluded that chemicals (surface and within) of conspecific eggs possibly attract neonates for egg–cannibalism, as both eggs and aphids were consumed in greater numbers when coated with egg extracts. The reverse occurred when eggs and aphids were coated with aphid extracts.

Sibling cannibalism in aphidophagous ladybirds: its impact on sex-dependent development and body weight

Abstract:  The effects of sibling egg cannibalism on sex‐dependent development and adult body weight were determined by rearing simultaneously two groups of sibling larvae of ladybirds, viz. Propylea dissecta and Coccinella transversalis individually. The first group included cannibals (i.e. neonates, which took a sibling egg as the first meal and later fed on aphids, Aphis craccivora) and the other included non‐cannibals (reared exclusively on aphids). The cannibal larvae developed faster with heavier adults than non‐cannibals. This expedited development and nutritional advantage (increased body weight) was greater in first instars indicating maximum benefit of sibling cannibalism to them. Sibling cannibalism was relatively more advantageous to male than to female ladybirds. Laboratory data predict that the larger size of adults in the field could possibly be the result of sibling egg cannibalism at the neonate level.

Ovipositional Rhythmicity in Ladybirds (Coleoptera: Coccinellidae): A Laboratory Study

Complete and diel ovipositional rhythms have been observed in three aphidophagous ladybirds (Coleoptera: Coccinellidae): Coccinella septempunctata Linnaeus, Coccinella transversalis Fabricius and Propylea dissecta (Mulsant) for the first time. The complete ovipositional rhythm could be described in terms of a polynomial curve and daily fluctuations in all three species. In the diel cycle, all three ladybird species oviposited significantly in the scotophase. C. septempunctata females preferred to oviposit at the end of scotophase in the early morning hours (0300–0700), P. dissecta laid most eggs in the middle of scotophase during the night (2100–2300), and C. transversalis laid most at the beginning of the scotophase at dusk (1700–1900). While the diel ovipositional rhythm of C. septempunctata and P. dissecta did not differ between days, that of C. transversalis changed dramatically; there was a single peak on the first and second day of observation, and four oviposition peaks on the fifth day with the peaks being situated in the two hours preceding and succeeding the onset and end of the scotophase. Diel rhythms of C. septempunctata and P. dissecta appear to be endogenous in nature while that of C. transversalis is partly modified by exogenous factors.

Attack, escape and predation rates of larvae of two aphidophagous ladybirds during conspecific and heterospecific interactions

Abstract The attack, escape and predation rates for larvae of aphidophagous ladybird Propylea dissecta (Mulsant) and Coccinella transversalis Fabricius were quantified as a potential mechanism leading to the differences in the incidence of cannibalism and intraguild predation. These rates were compared at four larval instars within and between the species. The attack rates of larvae of C. transversalis were significantly higher than those of P. dissecta towards conspecific and heterospecific victims. For both species, third instars exhibited maximum tendency to attack. Escape rates in C. transversalis were higher than P. dissecta. In P. dissecta, the second instars made a greater number of escapes than other conspecific instars after being attacked by same stage cannibal or heterospecific predator. In P. dissecta, first instars suffered maximum mortality due to cannibalism and intraguild predation by conspecifics and heterospecifics of the same and older developmental stage. No larvae of C. transversalis were eaten by P. dissecta of the same stage. These results suggest that the larvae of P. dissecta were more often potential cannibals than intraguild predators, while the reverse was the case in C. transversalis. Based on this finding, it could be predicted that in patchy prey habitats, high rates of larval cannibalism in P. dissecta would occur with a high risk of cannibalism of first instars. Larvae of C. transversalis would respond as intraguild predators, while those of P. dissecta as intraguild prey. The greater size and walking activity of C. transversalis could be possible reason for this tendency.

Survival, development and life tables of two congeneric ladybirds in aphidophagous guilds

Abstract Two congeneric aphidophagous ladybirds, Coccinella septempunctata and Coccinella transversalis, were reared on three aphid species, Lipaphis erysimi, Myzus persicae and Aphis nerii, to estimate the effect of prey quality and intra‐ and interspecific interactions on their survival and development of life stages. Mortality of first instar ladybirds of both species was highest feeding on A. nerii. Preimaginal mortality was lowest when feeding on L. erysimi (C. septempunctata, 1.6% and C. transversalis, 3.2%), and highest when feeding on A. nerii (C. septempunctata, 6.2% and C. transversalis, 8.2%). Comparatively higher weight and larger size of C. septempunctata along with the lower levels of mortality recorded suggested that it is more likely to have acted as an intraguild predator than C. transversalis. High recorded mortality of C. transversalis is attributed to probable intraguild predation on account of its smaller size. The major sources of mortality were probably cannibalism, intraguild predation and other unknown factors. Lower prey quality increased the incidence of cannibalism and intraguild predation, especially in C. transversalis. The investigation suggests an intrinsic competitive advantage for C. septempunctata over C. transversalis in guilds of three aphid species.

On the optimization of soft magnetic properties of high Bs Fe83.7B14.8Cu1.5 nanocrystalline alloy

Influence of thermal annealing as a function of temperature and time, in Fe83.7B14.8Cu1.5 alloy was monitored using magnetic measurements, differential scanning calorimetery (DSC), X- ray diffraction (XRD) to get information on correlation between structure, formed nano-crystalline phases and soft magnetic properties. Thermal annealing dependence of coercivity (Hc) and saturation magnetization (B2000) shows that these values are affected by the structural relaxation and the presence of the precipitated nanocrystals in the amorphous phase. For the studied samples lowest coercivity of 14.6 A/m and rather high saturation induction value of 1.99 Tesla was obtained after annealing at 390 oC/1h. Activation energy of crystallization is 1.82 ± 0.48 eV. Grain diameter and volume fraction of the nanograins varies between 16.5 − 29 nm and between 2 − 56 % respectively. Lattice parameter suggests the presence of α-Fe and Fe23B6 phase.