The relative proportions of free amino acids as well as the amino acid compositions of hydrolysed unprecipitated peptides and hydrolysed whole carcasses were quantified for two aphid species: the gall-dwelling social aphid Pemphigus spyrothecae and the pea aphid Acyrthosiphon pisum. The whole-tissue amino acid profiles of the two taxonomically distant species had a surprisingly high level of correspondence. In contrast, when comparing the A. pisum profiles obtained in the current study to those obtained in an earlier study, major differences were identified. It is concluded that there are good prospects for developing an artificial diet for P. spyrothecae. There may also exist considerable scope for tailoring the existing diets of A. pisum to suit specialised populations which develop poorly on the standard diet. The amino acid profile of P. spyrothecae is the first such profile that has been reported for a gall-forming aphid.
Functioning of plant-aphid-natural enemy interactions may be associated with the structure and composition of withinfield vegetation, neighborhood fields and field borders, and the regional plant community of cropped and noncropped areas. Farmand region-scale vegetation in the wheat-growing area of the North American Great Plains was hypothesized to effect the abundance of two hymenopteran parasitoids, that differ in physiological and behavioral attributes, of the key pest aphid of wheat, Diuraphis noxia (Mordvilko). The parasitoids had greater sensitivity to farm-scale vegetation (wheat strip rotation with or without spring-sown sunflower) than region-scale vegetation (degree of diversification with other crops and wheat fields converted to conservation grasslands). A two-way factorial design of scale (farm- and region-scale) revealed that parasitoid abundance in grass-dominant (homogeneous) areas especially benefited from adding sunflower to the wheat-fallow strip crop rotation. Considerable sensitivity of the analysis was added when adjusting for seasonality of vegetation, revealing that the region-scale effects were most prominent late season. From a management viewpoint, adding sunflower into the wheat production system, especially in relatively homogeneous vegetation regions, tends to promote local parasitoid populations during the summer when spring-sown plants are maturing and wheat is not in cultivation. Contrasting results for A. albipodus and L. testaceipes were consistent with expectations based on behavioral and physiological attributes of the two aphid parasitoid families they represent. Still, the general management interpretation seems robust for the two parasitoids and has relevance to both farm- and region-scale management schemes that are occurring in the wheat production zone of North American Great Plains.
Winter climate determines the success of the two main reproductive strategies employed by aphids. Permanent parthenogens survive as parthenogenetic females in mild winters, but are regularly eliminated by low temperatures; while cyclical parthenogens, which switch to sexual reproduction by the end of summer, produce every year fertilised diapausing eggs resistant to frost.
We have studied the variation in sexual morph production of several clones of the cereal aphid Rhopalosiphum padi (L.) showing both strategies. Twenty clones of this species differing by their geographic origin and their mode of reproduction were placed in two laboratory environments mimicking the changes of photoperiod and thermoperiod occurring naturally from the end of summer and during the autumn in oceanic and continental conditions. The analysis of clonal responses in both climatic conditions showed (i) a wide variation in investment of clones in sexual reproduction with, in particular, evidence for a mixed strategy employed by clones producing both sexuals without ceasing parthenogenetic reproduction, (ii) no geographic adaptation among clones belonging to cyclical parthenogenetic populations, (iii) an earlier production of sexuals in continental conditions and a higher production of males in oceanic conditions.
Furthermore, we have compared the dates of first appearance of sexuals in our experiments with those occurring in the field based on a suction trap database and found that sexuals were caught in nature at least four weeks earlier than in the lab. These results underline the need for a better understanding of the influence of the whole array of environmental factors inducing the transition from parthenogenetic to sexual reproduction in aphids., Maurice Hullé, Damien Maurice, Claude Rispe, Jean-Christophe Simon, and Lit
The aphid alarm pheromone is known to trigger wing induction in pea aphids (Acyrthosiphon pisum). In reaction to alarm pheromone, aphids drop off the plant or walk away. While searching for a new feeding site they repeatedly encounter other members of the aphid colony and this increased contact rate is assumed to be important for wing induction ("pseudo-crowding" hypothesis). Because the encounter rate is a function of aphid colony size, wing induction in aphids in the presence of a predator should be a function of the number of aphids on the plant. We placed two, seven or 13 adult pea aphids on bean plants, and exposed the different-sized colonies to synthetic alarm pheromone to test the density-dependence of predator-induced wing induction. The mean percentage of winged morphs among the offspring produced on the plants ranged from 10 to 80 percent and increased both with aphid number and exposure to alarm pheromone. There was no synergy between aphid number and alarm pheromone exposure indicating that both factors are additive. The implications for aphid metapopulation dynamics are discussed.
The pea aphid, Acyrthosiphon pisum (Hemiptera: Aphididae), is a well-studied species in terms of its colour polymorphism, where it occurs as two distinct colour morphs, red and green. It is proposed that the occurrence and maintenance of this polymorphism is an adaptive response to environmental factors, in particular natural enemies and host plant quality. We hypothesized that these adaptations are directly mirrored in the energy reserves accumulated by the different colour morphs during their pre-adult stages and reflect their specialization for particular ecological roles. We quantitatively measured the different energy reserves of red and green pea aphids and found that the total energy reserves of these morphs did not differ. Interestingly, these reserves were made up of different components in the red and green colour morphs. There was a higher percentage content of water-soluble carbohydrates and lipids in the red clones and higher percentage content of protein in green clones. These finding are in accordance with green clones being more fecund than red ones and needing more protein for reproduction than red clones, which produce more winged offspring when crowded or in response to the presence of natural enemies and so, need more lipids and carbohydrates to fuel their walking and flight. Apparently, different colour morphs are physiologically specialized to adjust their energy reserves in relation to their specific ecological adaptations and maximize their fitness in terms of dispersal, reproduction, defense and survival., Seyed Mohammad Ahsaei ... []., and Obsahuje seznam literatury
Ant-aphid mutualism is considered to be a beneficial association for the individuals concerned. The population and fitness of aphids affected by ant attendance and the outcome of this relationship affects the host plant of the aphid. The main hypothesis of the current study is that ant tending decreases aphid developmental time and/or increases reproduction per capita, which seriously reduces host plant fitness. The effect of attendance by the ant Tapinoma erraticum (Latreille, 1798) (Hymenoptera: Formicidae) on population growth and duration of different developmental stages of Aphis gossypii Glover (Hemiptera: Aphididae) were determined along with the consequences for the fitness of the host plant of the aphid, Vicia faba L., in greenhouse conditions. The initial aphid density was manipulated in order to study aphid performance due to density-dependent changes in ant attendance. The population growth rate of ant attended aphids was more than that of unattended aphids. However, the ratio of 1st-2nd nymphs to adults in aphid populations attended by ants was lower. The yields of bean plants on which the aphids were attended by ants were significantly greater than those of unattended plants. This study indicates that ants not only increase aphid fitness in terms of their population growth rate, but also benefit the host plant., Afsane Hosseini, Mojtaba Hosseini, Noboru Katayama, Mohsen Mehrparvar., and Obsahuje bibliografii
The factors that affect the local distribution of the invasive Harmonia axyridis are not yet completely resolved. Hypotheses predicting positive and independent effects of prey abundance and degree of urbanization on the adult abundance of this species in Central Europe were tested. Populations of H. axyridis were sampled in a period when it was most abundant, by sweeping lime trees (Tilia spp.) at 28 sites along a 20 km transect across urban (western Prague) and surrounding rural areas. The sites differed in aphid abundance (number of Eucallipterus tiliae per 100 sweeps) and degree of urbanization (percentage of the surrounding area within a 500 m radius covered by impervious human constructions). Multiple linear regression analysis of log-transformed data revealed that abundance of H. axyridis (number of adults per 100 sweeps) increased significantly with both aphid abundance (P = 0.015) and urbanization (P = 0.045). The positive relationship between degree of urbanization and abundance of H. axyridis was thus not a side effect of variation in aphid abundance, which was also greater in urban than rural areas. The effect of urbanization might constrict the habitat available to H. axyridis and force this species to aggregate in urban green "refugia". These results point to a plurality of factors that determine coccinellid abundance at natural sites.
The aphid Tuberculatus quercicola (Matsumura), a non host-alternating species, lives on Daimyo oak, Quercus dentata Thumberg, and other species of oak. In summer there was a significant reduction in the total amino acid concentration in phloem sap of the host plant and fecundity of the aphids. There are two phenotypes of Q. dentata: one produces flush leaves in mid-July and the other does not. This study investigates the effect of the flush leaves produced by Q. dentata in summer on the density, fecundity and honeydew excretion by T. quercicola. Of 20 shoots on each of the study trees, 6-13 (average 8.8 shoots) produced secondary shoots with flush leaves. The number of aphids on flush leaves sharply increased by two-fold compared to that on mature leaves. The aphids reared on flush leaves were significantly larger and had a larger embryo number compared to those on mature leaves. These results suggest that the phloem sap of flush leaves has a high nutritive quality for aphids. However, in mid-summer and early autumn T. quercicola went into reproductive diapause regardless of whether it was reared on flush or mature leaves. Aphid colonies persisted until October even on trees that did not produce secondary leaves. These observations suggest that this aphid does not depend on secondary leaf production. Thus, the use of flush leaves does not enable T. quercicola to avoid nutritional stress in summer and the need for reproductive diapause.
The rose aphid, Macrosiphum rosae, living on rose var. Black Magic, was reared in the laboratory at four constant temperatures 15, 18, 22 and 25 ± 1°C, 75 ± 5% R.H. and 14L : 10D. Parameters investigated included developmental rate, survival, pre-reproductive delay and fecundity. The rate of nymphal development (0.17) was greatest at 22°C. The longest developmental time (12.33 days) was recorded at 15°C. The generation time was longest and shortest at 15°C and 22°C respectively. The lower developmental threshold was calculated to be 9.05°C. Based on this, the degree-day requirement from birth to adulthood was found to be 77.5 dd. The pre-reproductive delay also decreased markedly with increase in temperature from 15°C to 22°C. The longest lifespan of apterous females (12.38 d) was observed at 15°C, whereas the shortest (8.06 d) was at 25°C. The mean adult longevity declined with increase in temperature from 15°C to 25°C. The fecundity of females (progeny/female) increased from 11.38 to 28.88 with increase in temperature from 15°C to 22°C but then decreased to 8.38 as the temperature increased from 22°C to 25°C. The largest (0.311) and smallest (0.113) rm occurred at 22°C and 15°C respectively. All of the parameters of the M. rosae life cycle at the four temperatures tested were optimum at 22°C. This Iranian population of M. rosae can develop at lower temperatures than an Australian population.
This paper examines some biological aspects and the predatory capacity of Chrysoperla externa fed nymphs of Sipha flava and reared at different temperatures. Recently hatched larvae were placed individually in Petri dishes, fed ad libitum with S. flava and reared at either 12, 16, 20, 24, 28 or 32 ± 1°C, a RH of 70 ± 10% and a 12-h photophase. The experiment was fully randomized with 30 replicates of each treatment. The duration and survival in each instar, and larval and pupal stages (pre-pupa + pupa) were analyzed. To determine the predatory capacity of larvae they were each provided daily with three-day-old nymphs of the aphid, in a number greater than they could consume. Ninety C. externa larvae were kept individually in Petri dishes at 24 ± 1°C, and their daily consumption recorded during development. Temperature influenced the rate of larval and pupal development. There was a decrease in the duration of development with increase in temperature. Regression analyses, based on quadratic equations, were used to describe the effect of temperature on the duration of development in the different instars of C. externa. This revealed that the base temperature increased as the larvae developed towards the adult phase. The survival of larvae in the first and second instars was similar at 12, 16, 20, 24, 28 and 32°C but none of the third instar larvae completed their development at 12°C and 32°C. The average daily and total consumption of aphids by third instar larvae was about 48 times greater than that of first instar larvae. The larvae ate an average of 10, 37 and 479 aphids in the first, second and third instars, respectively.