Rearing the Mexican beetle Zygogramma bicolorata (Chrysomelidae: Coleoptera) on a semi-synthetic diet

A semi-synthetic diet utilising parthenium leaf powder was evaluated for rearing the Mexican beetle Zygogramma bicolorata Pallister under in vitro conditions at 26±1°C, 65% RH. Significant differences were observed in the biological parameters of the beetle viz., the grub survival (54.3%), pupation (47.2%), fecundity (54.6/day) and total developmental period (37.7 days), when reared on the semi-synthetic diet compared to those when reared on natural parthenium leaves (91.5, 85.5, 74.8 and 29.8, respectively). The feasibility of utilising the semi-synthetic diet for mass production of the beetle is discussed.     

Benefits of polyandry in Parthenium beetle,Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae)

The influence of polyandry on the reproductive performance of females and on offspring fitness in Zygogramma bicolorata Pallister was investigated using four experimental treatments, viz. (A) monandrous, limited mating, (B) monandrous, unlimited mating, (C) polyandrous, no-choice limited mating, and (D) polyandrous, mate choice unlimited mating. Polyandrous females had higher reproductive performance than monandrous ones. Monandrous females subjected to unlimited matings had higher egg viability than those subjected to limited matings, but fecundity did not differ significantly. In polyandrous females, the freedom to choose mates did not affect reproductive performance. However, offspring of polyandrous females allowed mate choice developed fastest and had the highest survival at 25, 27, and 30 °C. Thus, polyandry in Z. bicolorata appears to provide both direct (material) and indirect (genetic) benefits resulting in better reproductive performance and increased adaptability of the offspring to counter environmental stresses. The present study not only adds to the knowledge of reproductive biology of Z. bicolorata but it could also be of economic value as it may help in the mass rearing of Z. bicolorata and in the management of Parthenium hysterophorus.     

Endogenously entrained life events of Parthenium beetle,Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae)

Biological rhythm is ubiquitous in all living organisms and is known to govern physiology, behavior, and population of insects. Though these rhythms are generated endogenously, they are entrained by environment. This experiment aims to evaluate the diel rhythms of mating, hatching and oviposition, and the influence of parental mating rhythm on their progeny. Peak of mating and oviposition incidences were recorded during later part of the photophase, which might be ascribed to the foraging rhythm during the day. However, maximum hatching was recorded during the scotophase which appears to be a survival strategy. Mating, oviposition, and hatching rhythms did not change on consecutive days and were thus probably endogenous in nature. It was also observed that the rhythm of parental mating had profound effect on their offspring fitness in terms of development and survival.     

Food consumption,utilization and ecological efficiency of Parthenium beetle,Zygogramma bicolorata pallister (Coleoptera: Chrysomelidae)

Food consumption, utilization and ecological efficiency of Zygogramma bicolorata were studied in larvae and adults up to 45 days old. The study revealed that sex had a significant influence on dry food consumption in adults but not in larvae. The other parameters of ecological efficiencies, viz. efficiency of conversion of ingested food (E.C.I.), tissue growth and dry biomass, were highest in the fourth instar and in adult females. The Consumption Index (C.I.) was higher in males than females in both larval and adult stages. Developmental and growth rates were relatively higher in the first and second instars. The fourth instar and adult females were the most efficient consumers and converters of food. Food intake by females was an important determinant of the number of eggs laid.     

Influence of age at mating on the reproductive performance of Parthenium beetle,Zygogramma bicolorata (Coleoptera: Chrysomelidae)

Abstract Age-specific mating incidence, sexual maturation and effect of age at mating on reproductive performance of the Parthenium beetle, Zygogramma bicolorata Pallister, was studied. Based on 50% mating incidence the calculated age of sexual maturation of males and females was 10.5 and 11.1 days, respectively, which was not statistically significant. However, on the basis of age at first mating, that is, sexual maturity, females matured 2 days earlier than males. Fecundity, pre-oviposition, oviposition and post-oviposition period and female longevity appear to be influenced by female age at mating with reproductive performance peaking at 30 days. On the other hand, egg viability was influenced by male age and was highest when males mated at the age of 40 days. To summarise, egg production and timing of egg deposition was female age-dependent, whereas egg fertility was male age-dependent. It was also observed that females mated at a later age and laid a higher number of eggs immediately after mating than did earlier mated females. This was ostensibly in a bid to increase fitness by maximizing reproductive output in the reduced life span available. This is the first investigation on the effect of age of females at mating on reproduction in this beetle.     

不同环境变量下银胶菊叶甲的生命表(英文)

在室内研究了不同环境变量(如食物、温度、光周期和不同光波长)下银胶菊杂草Parthenium hysterophorus L.的食叶昆虫和生物防治因子银胶菊叶甲Zygogramma bicolorata Pallister 的生命表。不同发育阶段的该种叶甲取食银胶菊不同部位时,取食花的甲虫死亡率指标Kappa值最低,其次是取食叶片和茎;而取食花时甲虫世代存活率最高。温度显著影响主要发育阶段该种叶甲的死亡率和存活率。27℃下饲养的未成熟期甲虫的Kappa值最低,其次是30, 25, 20 和35℃。世代存活和存活率表现相同的趋势。不同光周期显著影响死亡率,在14L∶10D (长日照)下世代存活最好,其次是 12L∶12D (昼夜相等), 10L∶14D (短日照), 24L∶0D (连续光照) 和0L∶24D (连续黑暗)。甲虫对不同波长光的反应上,在白光（广谱）下Kappa值最低,世代存活率最高,其次是黄光（λ≈570 nm)、蓝光 (λ≈475 nm) 和红光(λ≈650 nm)。卵的死亡率最高。不同发育阶段的甲虫在27℃长日照白光下用银胶菊花饲养最佳。死亡率趋势具有严格和显著的阶段特异性,表现出内在的存活效应,与研究的因素无关。     

Post introductory risk assessment studies on Zygogramma bicolorata (Coleoptera: Chrysomelidae), a classical biological control agent of Parthenium hysterophorus (Asteraceae) in India

Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), a biological control agent of Parthenium hysterophorus L. (Asteraceae), was feeding on leaves of Helianthus annuus in India, raising concerns of its host range. Based on the age grading technique, it was shown that the majority of Z. bicolorata on sunflower plants at any time were reproductively immature. This establishes that Z. bicolorata does not pose any risk to sunflower in India.     

Dispersal of the parthenium beetle Zygogramma bicolorata (Chrysomelidae) in India

Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) of Mexican origin, released in Bangalore in 1984, was observed defoliating Parthenium hysterophorus L. (Asteraceae) in 1988, and had dispersed over 50 000 km² by 1992. The insect appears to have potential in reducing weed density in those parts of India having moderate weather conditions.     

Temperature and altitude modulate feeding attributes of Mexican beetle,Zygogramma bicolorata Pallister on Parthenium hysterophorus

Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) is an effective biocontrol agent of Parthenium hysterophorus L. which is an alien invasive herbaceous weed with a pan-tropical distribution. The present study aimed to assess the effects of temperature and altitude on feeding attributes (consumption rate, conversion efficiency and growth rate) of adults from the wild populations of Z. bicolorata inhabiting India and Nepal. Results revealed that adults inhabiting areas of low temperature (24°C ‒ 25°C) and high altitude (415 m ‒1400 m) were large and had higher food consumption rates. In contrast, those inhabiting areas of high temperature (34°C ‒ 36°C) and low altitude (81 m ‒ 229 m) were smaller and had higher food utilization efficiencies. In all the eco-climatic regions, females were larger than males and had higher feeding attributes than their counterparts. Temperature between 27°C and 30°C was found optimal for Z. bicolorata adults to convert and utilize the food biomass to body mass. Above the optimal temperature the feeding attributes decreased. Present results suggest that there exists a possibility for decrease in body size, and thereby weed biocontrol efficiency of Z. bicolorata adults with an increase in temperature due to global climate change.     

Stage specific feeding attributes and mobilization of nutrients in Mexican beetle,Zygogramma bicolorata Pallister on Parthenium hysterophorus L.

Parthenium hysterophorus L. (Asteraceae) is a toxic weed of agricultural farms, pastures and wastelands with a pan-tropical distribution. The weed causes a reduction in crop production of agricultural fields and severe health problems in humans. The Mexican beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) is among the most promising candidates for the weed biocontrol. However, no previous study has evaluated assimilation of nutrients in this beetle. In the present study, feeding attributes and assimilation of nutrients by larvae of Z. bicolorata were assessed on the weed. Results revealed that the first larval instars of Z. bicolorata exhibited lowest consumption rates, and accumulated minimum concentrations of glucose, proteins and triglycerides in their body. They showed compensatory feeding, and displayed highest food utilization efficiencies and developmental rates. In contrast, the fourth larval instars exhibited higher food consumption rates and conversion efficiencies, but displayed lowest developmental rates. Accumulation of food reserves was also recorded maximum for the fourth larval instars. Overall, the findings may aid current mass-rearing efforts for Z. bicolorata in laboratories, but field trials are still needed to strengthen the present findings.     

Effect of egg cannibalism on mating preferences and reproductive fitness of Menochilus sexmaculatus Fabricius (Coleoptera: Coccinellidae)

Cannibalism has been reported in a large proportion of coccinellids in fields as well as in laboratories but studies involving mate preferences and potential benefits of cannibalism on reproduction in Menochilus sexmaculatus Fabricius (Coleoptera: Coccinellidae) have yet not been done. Thus, we assessed the effect of conspecific egg cannibalism on mate preferences and reproductive outputs including offspring development. Higher mate preferences were recorded for non-cannibalistic mates (fed on A. craccivora) than cannibalistic ones (fed on conspecific eggs). Mating parameters were significantly influenced by cannibalism. Time to commence mating lasted less for homogeneous diet pairs than heterogeneous diet pairs. Longer copulation duration and higher fecundity were recorded when one of the individuals in mating pair or both was a non-cannibal. Egg viability did not differ significantly in all the reciprocal crosses. In addition, the total developmental durations of offspring were similar for all mating pairs.     

Seasonal variation in the effectiveness of the leaf-feeding beetle Zygogramma bicolorata (Coleoptera: Chrysomelidae) and stem-galling moth Epiblema strenuana (Lepidoptera: Tortricidae) as biocontrol agents on the weed Parthenium hysterophorus (Asteraceae)

Variation in the effectiveness of biocontrol agents on the weed Parthenium hysterophorus L. was evaluated at two properties (Mount Panorama and Plain Creek) in Queensland, Australia for four years (1996-2000) using a pesticide exclusion experiment. At Mount Panorama, higher levels of defoliation by the leaf-feeding beetle Zygogramma bicolorata Pallister and galling by the moth Epiblema strenuana Walker in 1996-97 coincided with an above average summer rainfall, but in the following three years with below average summer rainfall the defoliation and galling levels were significantly lower. Biocontrol had significant negative impact on the weed only in 1996-97 with no major impact in the following three years. At Plain Creek, galling by E. strenuana was evident in all the four years, but varied significantly between years due to non-synchrony between P. hysterophorus germination and E. strenuana emergence. At Plain Creek biocontrol had limited impact on the weed in 1996-97 and 1997-98, with no significant impact in the following two years. Over the 4-year period, defoliation and galling resulted in 70% reduction in the soil seed bank at Mount Panorama, but the reduction in the soil seed bank at Plain Creek due to galling was not significant. Effectiveness of Z. bicolorata and E. strenuana was dependent on weather conditions and as a result had only limited impact on the weed in three out of four years.     

Effect of photoperiod on slow and fast developing individuals in aphidophagous ladybirds,Menochilus sexmaculatus and Propylea dissecta (Coleoptera: Coccinellidae)

The effects of environmental parameters on insect development have been studied extensively. But the reasons for 2 differential developmental rates within same cohort under varying environmental factors have not been explored. For the purpose, in this study the existence and stability of slow and fast development under 5 photoperiods (i.e., 8L: 16D, 10L : 14D, 12L : 12D, 14L : 10D and 16L : 8D; light and dark hours per day) and its effect on body mass and reproductive attributes in 2 aphidophagous ladybirds, Menochilus sexmaculatus (Fabricius) and Propylea dissecta (Mulsant) was examined on Aphis craccivora Koch at 27 ± 1 °C temperature. A clear bimodal (2 peaks, where the first peak represented the fast developing and the 2nd peak slow developing individuals) pattern of distribution at each photoperiod was found. The proportion of slow and fast developing individuals in a cohort differed with photoperiods. The slow developing individuals were more in numbers at 8L : 16D, in equal numbers at 14L : 10D and in less numbers at 16L: 8D, indicating that the variation in emergence was owing to exogenous cues influenced differential rates of mortality. Slow developing individuals had female biased sex ratio, higher longevity and lower body mass than fast developing individuals. Fast developing females laid higher numbers of eggs with higher egg viability than slow developing females. Study of such variations in development at different photoperiods is helpful to understand its role in the development of insects particularly ladybirds and permits the selection of fast developing bioagents for their use in biocontrol of pest species.     

Effects of temperature on the expression of elytral colour polymorphism in the ladybird beetle,Menochilus sexmaculatus (Coleoptera: Coccinellidae)

The ladybird beetle, Menochilus sexmaculatus (Fabricius), has a remarkable elytral colour polymorphism composed of black and red. In the present study, we investigated the effect of temperature on growth from the first instar larva to the pupal stage, as well as maternal morph types on the phenotypic expression of the elytral colour morph in a polymorphic population from Osaka, Japan. Female individuals of three different elytral colour morphs were collected from a wild population, and hatchlings from each female were divided into three groups, which were reared at three constant temperatures: 20 °C, 25 °C, and 30 °C. The phenotypic frequency of F₁ adults indicated that the elytral morph type was determined by genetic factors, but not by growth temperatures. Namely, type A (almost black morph) was the most abundant in F₁ from type A mothers (Male: 52.6%; Female: 32.3%); and types B (four small-dotted morph) and F (four medium-dotted morph) were the most abundant from type B (Male: 56.7%; Female: 53.3%) and type G (four larger-dotted morph) mothers (Male: 33.3%; Female: 31.3%), respectively. Therefore, the expression of elytral colour polymorphism in the Osaka, Japan population is likely to have a genetic basis contingent on parental morphs, rather than a phenotypic plasticity associated with growth temperatures.     

Mating prior to overwintering in the imported willow leaf beetle, Plagiodera versicolora (Coleoptera: Chrysomelidae)

Abstract. 1. We report on the mating status of overwintering adults of the imported leaf beetle, Plagiodera versicolora Laicharting. This species overwinters as adults, under the bark of willow trees.
2. Individuals were collected both in the autumn, just after initiation of diapause, and in the spring, just before natural termination of diapause. From the autumn sample, we discovered that diapause can be terminated by husbanding the adults at 4°C for 4 weeks.
3. Most females lay fertile eggs upon the termination of diapause; however, a significant number of females lay non-fertile eggs after overwintering in the field.
4. Many females mate with more than one male before entering diapause. Progeny analysis using allozyme genetic markers shows that, on average, females who are fertile upon termination of diapause utilize sperm from 1.2 males to fertilize their eggs.     

Endemism patterns in the Italian leaf beetle fauna (Coleoptera,Chrysomelidae)

In this contribution the results of a zoogeographical analysis, carried out on the 123 endemic leaf beetle species (Coleoptera: Chrysomelidae) occurring in Italy and its immediately adjacent regions, are reported. To assess the level of faunistic similarity among the different geographic regions studied, a cluster analysis was performed, based on the endemic component. This was done by calculating the Baroni Urbani & Buser’s similarity index (BUB). Finally, a parsimony analysis of endemicity (PAE) was used to identify the most important areas of endemism in Italy.     

广西叶甲亚科昆虫种类记述(鞘翅目:叶甲科)

记述中国科学院动物研究所 1 998～ 2 0 0 0年对广西十万大山及大瑶山地区考察所采获叶甲亚科并该所标本馆馆藏叶甲亚科标本及文献记载 ,共 2 0属 35种 ,其中包括1中国新记录属 Pseudolina Jacoby、1新种 Gonioctena( Brachyphytodecta) oculata sp.nov.、2中国新记录种 Pseudolina indica Jacoby,Paropsides bouveri Chen。模式标本保存在中国科学院动物研究所。     

Host range and risk assessment of Zygogramma bicolorata,a defoliating agent released in South Africa for the biological control of Parthenium hysterophorus

Parthenium hysterophorus (parthenium) is a weed of international importance and is spreading rapidly in sub-Saharan Africa. Consequently, it has been targeted for biocontrol in South Africa since 2003. Based on precedents elsewhere in the world, the defoliating beetle Zygogramma bicolorata was prioritised as a candidate agent. Although no-choice tests, involving some 48 test plant species, indicated a significant preference for parthenium, significantly reduced feeding and oviposition was recorded on some species. Multiple-choice tests resolved many of these non-target results; however, Helianthus annuus (sunflower) was still selected for oviposition and feeding. Of the 12 sunflower cultivars tested, four were selected for oviposition, while two were selected for oviposition and feeding. These six cultivars were then subjected to larval development trials, together with three native and two weed species (in the Asteraceae). These trials showed high levels of complete development on parthenium, significantly reduced development on sunflower cultivars, and partial development on only one of the weed species. Finally, a risk assessment was conducted on the six sunflower cultivars to quantify Z. bicolorata feeding and reproductive performance. Feeding risk calculations revealed these cultivars to have an extremely low risk (<0.2%) of supporting Z. bicolorata feeding and development. Similarly, reproductive risk calculations showed a very low risk (<0.16%) of supporting viable Z. bicolorata populations. These data are supported by findings from both the native (Mexico) and introduced ranges (Australia, India) of Z. bicolorata, where it has never been recorded as a pest of sunflower. These considerations were accepted by the regulatory authorities and in August 2013, Z. bicolorata became the second insect agent to be released in South Africa for the biocontrol of parthenium.