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

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 mortafity 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.

Comparative Characterization of the Ladybird Beetles (Coleoptera: Coccinellidae) from Hazara University, Garden Campus, Mansehra, Pakistan

The ladybird beetles (Coleoptera: Coccinellidae) have great economic importance as natural enemies. Three hundred individuals belonging to 6 genera and 7 species of the subfamily, Coccinellinae and the tribe, Coccinellini was collected during March-May, 2011 from 3 study sites of Hazara University, Garden Campus, Mansehra, Pakistan. They were reported maximum (83.3%) from residential area and minimum (8%) from administration area. All collected species have glabrous hair on their slightly elongated or rounded bright colored body. The seven-spotted ladybug, Coccinella septempunctata (Linnaeus) has maximum (average: 6.7 ± 0.77 cm;n = 15) and Adalia tetraspilota (Hope) has minimum (average: 4.2 ± 0.15 cm;n = 14) body length. Moreover, transverse ladybird, Coccinella transversalis (Fabricius) has maximum (average: 4.8 ± 0.35 cm;n = 10) and Oenopia sauzeti (Mulsant) (n = 9) or adonis ladybird, Hippodamia variegate (Goeze) (n = 10) has minimum (3.1 cm) body width. Except six-spotted zigzag ladybird, Menochilus sexmaculatus (Fabricius) (n = 12), all collected species have black head, varied but attractive and dark in color pronotum and elytra, black scutellum except in fifteen-spotted ladybird, Harmonia dimidiate (Fabricius) (n = 10) which was brownish. The ventral side of body of A. tetraspilota was dark brown, however, C. septempunctata, C. transversalis, H. variegate and O. sauzeti were black;moreover, H. dimidiata was brownish-orange;further, M. sexmaculatus was brown. It is concluded that ladybird beetles of HU have great diversity. Their further studies have been needed for education and awareness.

Gut microbiota variation across generations regarding the diet and life stage in Harmonia axyridis (Coleoptera: Coccinellidae)

We attempt to determine the effect of the dietary switch from a native to non-native prey on the gut microbiota in the predaceous ladybird Harmonia axyridis larvae and adults and examine how the dietary effect may vary across generations.We fed H.axyridis with different diets,native aphid Megoura japonica(Matsumura)versus non-native mealy-bug Phenacoccus solenopsis(Tinsley),for 5 generations and sequenced microbes in the gut of the 3rd instar larvae and adults of the Ist,3rd,and 5th generations.In addition,we identified microbes in M.japonica and P solenopsis.The 2 prey species differed in microbial community as measured by abundances of prevalent microbial genera and diver-sity.In H.axyridis,abundances of some prevalent microbial genera differed between the 2 diets in the 1st and 3rd generations,but the difference disappeared in the 5th generation;this tendency is more obvious in adults than in larvae.Overall,gut microbial assemblages became gradually cohesive over generations.Microbial diversity differed between diets in the 1st and 3rd generations but became similar in the 5th generation.Major prevalent gut microbial genera are predicted to be associated with metabolic functions of H.axyridis and associated genera are more abundant for consuming the mealybug than the aphid.Our findings from this study suggest that the gut microbiota in H.axyridis is flexible in re-sponse to the dietary switch,but tends toward homogeneity in microbial composition over generations.

Aphidophagous guilds on nettle （Urtica dioica） strips close to fields of green pea, rape and wheat

The common nettle （Urtica dioica L.） is a perennial and cosmopolitan plant species and is known to be the source of food for a great diversity of insects. To understand the importance of the nettle in agro-ecosystems, a field experiment was carried out in an experimental farm at Gembloux （Belgium） to study the effect of nettle margin strips on aphid and aphidophagous populations in close field crops, namely wheat （Triticum aestivum L.）, green pea （Pisum sativum L.） and rape （Brassicae napus L.）. The aphids and related beneficial populations were weekly assessed, from March to August 2005, by visual observations in two plots per field crop. A higher abundance of aphidophagous beneficials was collected in nettle strips when compared to the field crops. Particularly, the presence of predatory anthocorids, mirids and green lacewings was observed on nettle only. Nevertheless, the most abundant aphid predatory family, the Coccinellidae, was distributed in both environments, in nettle strips and in crop fields. The field margin supported a significantly higher density ofHarmonia axyridis than the field crops. In contrast, the field crops, green pea particularly, supported a higher density of Coccinella septempunctata. The distribution of the aphidophagous species, mainly the ladybirds, was discussed in relation to the host plant and related aphid species and their potential effect on integrated pest management.

Aphids-induced plant volatiles affect diel foraging behavior of a ladybird beetle Coccinella septempunctata

The ladybird beetle Coccinella septempunctata(L.)is an important biocontrol agent of pests such as various aphid species.Despite being one of the most studied coccinellid species,many aspects of its foraging behavior are still not completely understood.This study focuses on the diel foraging behavior of C.septempunctata,investigating their olfactory orientation toward aphid-infested plants,walking activity on plants and on the soil,and feeding rates.In the scotophase the ladybird beetles were significantly more attracted to the odor of aphid-infested plants,on which they also showed considerably higher walking activity then on uninfested controls.Females were more prone to utilize olfactory cues when searching for prey and fed at higher rates than males;this shows that they are better adapted to nocturnal activity,as they require higher food intake.Coccinella septempunctata have the same feeding rate during the scotophase as in the photophase.Our study shows that C.septempunctata has the potential to forage in the scotophase if prey is abundant.The results support the hypothesis that volatiles of aphid-infested plants can attract or arrest foraging adult ladybird beetles,even in the darkness,which makes a considerable contribution to efficient prey search and enhances feeding capacity.

Effect of age on reproductive attributes of an aphidophagous ladybird, Cheilomenes sexmaculata

The effect of both male and female age was investigated on certain reproductive attributes, viz. mating incidence, mating duration, fecundity, percent egg viability, ratio of reproductive and non-reproductive periods and reproductive rate, of an aphidophagous ladybird, Cheilomenes sexmaculata （Fabricius）. Females started mating at the age of 8 hours post-emergence （PE） and males at the age of 2 days PE. Mating in the laboratory was a maledominated phenomenon. The mating duration and reproductive rate of 10-day-old females when mated with males of varying ages increased up to the male age of 60 days, and thereafter decreased, whereas, fecundity, egg viability and ratio of reproductive and non-reproductive periods increased up to the male age of 50 days, and thereafter declined. However, when females of varying ages were mated with 10-day-old males, fecundity and reproductive rate increased up to 40 days of female age, respectively, then decreased. The ratio of reproductive and non-reproductive periods increased with increasing age of females. Mating age for optimal reproductive output was 10-50-day-old males and NE to 40-day-old females. Reproductive cessation in males was recorded after 50 days PE, whereas in females at the age of 40 days PE. Higher mating durations lead to elevated reproductive rates. Delay in the reproductive phase was positively correlated with longevity. The results of this study may aid mass multiplication of this ladybird by identifying and promoting usage of adults of optimal age, Our results also enhance our understanding of the effect of age on reproductive attributes in ladybirds.

Global attractivity of the predator-prey system for cotton aphid and seven-spot ladybird beetle with stage structure

It is well known that the cotton aphid is the major pest in cotton fields of Northwest China, and seven-spot ladybird is an important natural enemy among the various possi- ble natural enemies of cotton aphid. In order to increase the applications of population dynamics in integrated pest management and control the cotton aphids biologically, we need to understand the population dynamics of cotton aphid and their natural enemies. A delay predator prey system on cotton aphid and seven-spot ladybird beetle are pro- posed in this paper. Based on the comparison theorem and an iterative method, we investigate the global attra^tivity of the equilibrium points which have important bio- logical meanings. Furthermore, some numerical simulations were carried out to illustrateand expand our theoretical results, in which a conjecture to generalize the well-known Theorem 16.4 in H. R. Thiemes book was put forward, which was taken as the open problem. The numerical simulations show coexistence of periodic solution, confirming the theoretical prediction.

The failed invasion of Harmonia axyridis in the Azores, Portugal: Climatic restriction or wrong population origin?

We tested two questions:(i)whether the climatic conditions of the Azorean Islands in Portugal may have restricted the invasion of Harmonia axyridis across this archipelago and(ii)determine what population of this species could have a higher probability of invading the islands.We used MaxEnt to project the climate requirements of different H.axyridis populations from three regions of the world,and the potential global niche of the species in the Azorean islands.Then we assessed the suitability of the islands for each of the three H.axyridis populations and global potential niche through histograms analysis,Principal Component Analysis(PCA)of climate variables,and a variable-by-variable assessment of the suitability response curves compared with the climatic conditions of the Azores.Climatic conditions of the Azores are less suitable for the U.S.and native Asian populations of H.axyridis,and more suitable for European populations and the global potential niche.The PCA showed that the climatic conditions of the islands differed from the climatic requirements of H.axyridis.This difference is mainly explained by precipitation of the wettest month,isothermality,and the minimum temperature of the coldest month.We concluded that the climatic conditions of the Azores could have influenced the establishment and spread of H.axyridis on these islands from Europe.Our results showed that abiotic resistance represented by the climate of the potentially colonizable zones could hinder the establishment of invasive insects,but it could vary depending of the origin of the colonizing population.