Influence of rearing temperature on triacylglycerol storage in the pea aphid,Acyrthosiphon pisum

Total fatty acids in the pea aphid reared at low temperatures increased significantly compared to that at high rearing temperatures. This change is reflected in a large increase of myristic acid, which occurs exclusively in triacylglycerols. When aphids were moved from 25°C to a lower rearing temperature at 10°C, saturated fatty acids accumulated over time, reaching a maximum at 16th day. When aphids were moved to 4°C, a temperature below the developmental threshold, those aphids did not accumulate saturated fatty acids. Similar results were observed when aphids were exposed to sequential decrease in rearing temperature. However, both total fatty acids and myristic acid in the aphids from the treatments of sequential decreasing rearing temperature were significantly higher compared to those in the aphids from the treatments of sudden decreasing rearing temperature. This result, therefore, supports the hypothesis that cold‐adapted aphids can survive under threshold temperature for a longer period of time than noncold‐adapted aphids. Acetyl‐CoA carboxylase activity in the aphids at 25°C was twofold higher than that in the aphids at 10°C, whereas fatty acid synthase activities in the aphids reared at 25 and 10°C are similar. Aphids reared at 10°C showed a threefold reduction in reproduction rates. This reduced production of new nymphs reduces energy demand and would allow for accumulation of energy in the form of triacylglycerols. Therefore, the increased level of saturated fatty acids in aphids reared at low temperature is probably related to lower utilization of fatty acids rather than increased rates of biosynthesis.     

Influence of host size variation on the development of a koinobiont aphid parasitoid, Lysiphlebus ambiguus Haliday (Braconidae, Hymenoptera)

To determine whether host body size is the currency used by the aphidiine parasitoid, Lysiphlebus ambiguus Haliday (Hymenoptera: Braconidae), in assessing host quality, the aphid, Aphis fabae Scopoli (Homoptera: Aphididae), was reared at either high or low temperature to yield hosts of the same instar with different body sizes. Cohorts of A. fabae raised at 15 degrees C and 30 degrees C and exposed to individual female L. ambiguus in no-choice tests were successfully parasitized in all host stages from 1st instar nymphs to adults. However, younger and smaller aphids were more susceptible to parasitism than older and larger nymphs or adults, as measured by the number of mummies produced. For aphid cohorts reared at 15 degrees C, the proportion of female progeny, progeny adult size, and development time all increased linearly with aphid size at the time of attack. In contrast, for aphid cohorts raised at 30 degrees C, the proportion of female progeny and progeny adult size declined with aphid size, while development time remained unaffected. Through manipulation of host rearing temperature, we have shown that at cooler temperatures the koinobiont parasitoid, L. ambiguus, responds to host size in the same way as an idiobiont parasitoid, but that this response is compromised at higher temperatures. Our results suggest that differential mortality during development is likely to influence the observed secondary sex ratio in relation to aphid size for aphid cohorts raised at higher temperatures due to disruption of the activity of the host's primary endosymbiont and that such reduced nutritional quality of aphids cannot be compensated by increased development time.     

Biosynthesis of sorbic acid in aphids: An investigation into symbiont involvement and potential relationship with aphid pigments

Studies were undertaken to determine the role of symbionts and UV exposure in biosynthesis of the aphid-specific polyketides, sorbic acid and quinone pigments. Injection of adult potato aphids, Macrosiphum euphorbiae (Thomas), with the antibiotic rifampicin did not alter the level of sorbic or myristic acid in triglycerides of resultant progeny; pigmentation was also unaffected. However, antibiotic injection did produce marked physiological effects; progeny from injected aphids were smaller, slower to mature, and not fecund. Light microscopy confirmed that only 8% of rifampicin-treated aphids contained mycetocytes; thus, symbiont involvement in the production of this unusual UV-quenching short chain fatty acid is not supported. Following multigenerational exposure to long wavelength UV light, no substantial changes in sorbic acid content were detected in the potato aphid or the oleander aphid, Aphis nerii Fonscolombe. Pigments from UV-exposed oleander aphids had a peak absorbance at 390 nm, 70 nm lower than unexposed aphids. This suggests a photo-protective role for the pigments of the sunlight-inhabiting A. nerii; by contrast, no changes were observed in pigments of M. euphorbiae which usually feeds in the shade. Injection of adult potato aphids with sodium [1-¹⁴C]-acetate rapidly labeled both sorbic acid and pigments, particularly among the latter a yellow pigment which co-chromatographed with the dominant C15 yellow pigment of the oleander aphid. These data support the hypothesis that aphid C30 pigments are built up by coupling of “monomeric type” C15 pigments. Although aphid and not symbiont enzymes appear to synthesize these acetogenins, a possible biosynthetic link between sorbic acid and aphid pigments requires further clarification. © 1994 Wiley-Liss, Inc.     

Temperature-dependent development and population growth of Tetraneura nigriabdominalis (Homoptera: Pemphigidae) on three host plants

The root aphid Tetraneura nigriabdominalis (Sasaki) (Homoptera: Pemphigidae) is a pest of many Gramineae species; however, little is known about its biology and relationships with host plants. The objectives of this study were to quantify the effects of temperature on development, longevity, fecundity, and population growth of T. nigriabdominalis and to assess the effects of host plant on development of T. nigriabdominalis. The effects of temperature on performance of this root aphid were determined at 10, 15, 20, 25, 30, and 35 +/- 1 degrees C on rice roots, Oryza sativa L. Nymphal stages from birth to adult decreased from 46.3 d at 10 degrees C to 8.5 d at 30 degrees C. Aphid survival and development were lowest at 35 degrees C, and no aphid produced progeny at this temperature. Average adult longevity decreased from 23.3 d at 15 degrees C to 8.2 d at temperatures up to 35 degrees C. Average number of nymphs produced per female was highest at 25 degrees C; averaging near 30 nymphs per female, but it dropped to near zero at both 10 and 35 degrees C. The highest intrinsic rate of increase (r(m)) was 0.241 at 30 degrees C. Net reproductive rate (R(0)) ranged from 29.8 at 25 degrees C to 0.2 at 10 degrees C. The generation time (GT) decreased with increasing temperatures from 60.3 d at 10 degrees C to 13.8 d at 30 degrees C. In addition, root aphids reared at 30 degrees C on three host plants [O. sativa, Zea mays L. and Sorghum bicolor (L.) Moench] revealed that the developmental time of the nymphal stages averaged 6.9 d when reared on O. sativa and 10.7 d when reared on Z. mays. Comparison of the nitrogen content of the three host plants indicated that the root nitrogen content was highest in O. sativa. The effect of nitrogen content on aphid performance, however, is still not clear. Other factors, such as plant secondary chemistry, may play a role in affecting aphid performance.     

The influence of temperature on size as an indicator of host quality for the development of a solitary koinobiont parasitoid

The influence of aphid size on the host quality assessment and progeny performance of aphidiine parasitoids was examined using the mealy plum aphid parasitoid, Aphidius transcaspicus Telenga (Hymenoptera: Braconidae) and the black bean aphid, Aphis fabae Scopoli (Homoptera: Aphididae), as a readily acceptable alternate host. Aphid size in relation to stage of development was manipulated by rearing synchronous aphid cohorts at either 15 or 30 °C. At 15 °C, 2nd instar aphids were approximately the same size as 4th instar aphids reared at 30 °C. Cohorts of 30 aphids from each instar, reared at each temperature, were exposed to parasitism by a single parasitoid female for a period of 5 h. Overall susceptibility to parasitism did not vary between aphid cohorts, but the parasitoid response to aphid size differed significantly between rearing temperatures for both progeny sex ratio (parent female assessment of host quality) and larval growth and development (host suitability for parasitoid development). For aphids reared at 15 °C, the proportion of female progeny and emerging adult size for the parasitoid increased linearly with aphid size at the time of attack, while development time remained constant. In contrast, for aphids reared at 30 °C, the proportion of female progeny, emerging adult size, and the development time of the parasitoid all declined with aphid size at the time of attack. The contrasting responses of the parasitoid to host size for aphids reared at the two temperatures suggest that host quality is only indirectly related to aphid size among aphidiine parasitoids. The possible effects of higher temperatures on nutritional stress, obligate endosymbionts, and future growth potential of the aphids are discussed as explanations for the variation in host quality for parasitoid development.     

Demography of soybean aphid (Homoptera: Aphididae) at summer temperatures

Soybean aphid, Aphis glycines Matsumura, is now widely established in soybean, Glycine max L., production areas of the northern United States and southern Canada and is becoming an important economic pest. Temperature effect on soybean aphid fecundity and survivorship is not well understood. We determined the optimal temperature for soybean aphid growth and reproduction on soybean under controlled conditions. We constructed life tables for soybean aphid at 20, 25, 30, and 35 degrees C with a photoperiod of 16:8 (L:D) h. Population growth rates were greatest at 25 degrees C. As temperature increased, net fecundity, gross fecundity, generation time, and life expectancy decreased. The prereproductive period did not differ between 20 and 30 degrees C; however, at 30 degrees C aphids required more degree-days (base 8.6 degrees C) to develop. Nymphs exposed to 35 degrees C did not complete development, and all individuals died within 11 d. Reproductive periods were significantly different at all temperatures, with aphids reproducing longer and producing more progeny at 20 and 25 degrees C than at 30 or 35 degrees C. Using a modification of the nonlinear Logan model, we estimated upper and optimal developmental thresholds to be 34.9 and 27.8 degrees C, respectively. At 25 degrees C, aphid populations doubled in 1.5 d; at 20 and 30 degrees C, populations doubled in 1.9 d.     

Influence of constant temperatures on life history parameters of the cotton aphid, Aphis gossypii, infesting cotton

Laboratory clip-cage studies were conducted to quantify the temperature-dependent development, survivorship, and reproduction and to generate life history characteristics and population growth parameters of the cotton aphid, Aphis gossypii Glover, on phenologically standardized greenhouse-grown cottons at 10, 15, 20, 25, 30, and 35 degrees C. The developmental thresholds were estimated to be 6.3, 6.7, 5.9, 5.9, and 6.3 degrees C for first to fourth instars and for total nymphal development, respectively. The maximum rate of development were estimated to occur at 32.2, 30.8, 30.4, 30.0, and 30.2 degrees C for first to fourth instars and for total nymphal development, respectively. Increased temperature resulted in more rapid decline in survivorship, which was particularly sharp at 35 degrees C, dropping from 94 to 17% in 5 d. Number of days elapsed until first deposition of progeny increased progressively and sharply at temperatures 10 (26 d) to 15 (15 d) to 20 degrees C (8 d) and stabilized at 5 d for 25, 30, and 35 degrees C. Average lifetime fecundity of females rose from a low of 9.76 progeny at 10 degrees C to a peak of 58.9 progeny at 30 degrees C and declined sharply to 17.3 at 35 degrees C. Finite rate of population growth was highest at 25 degrees C and lowest at 10 degrees C. Although stage-specific developmental maxima occurred between 30 and 32 degrees C, a nonlinear regression model estimated 28.6 degrees C to be the optimum temperature for overall cotton aphid development, reproduction, and population increase.     

Effect of temperature and cultivar on pea aphid, Acyrthosiphon pisum (Hemiptera: Aphididae) life history

Life history parameters of the pea aphid, Acyrthosiphon pisum were studied at five constant temperatures on two cultivars of peas, Scout and Sancho. The development and mortality of juveniles and the life-span, age-specific fecundity and survivorship of adult aphids were recorded and used to construct life tables. The juvenile development period (from birth to adulthood) was longest at 11.9 degrees C (16.8 days on cv. Scout and 16.2 days on cv. Sancho) and shortest at 26.7 degrees C (8.5 days on cv. Scout and 8.8 days on cv. Sancho). At all temperatures, except 26.7 degrees C, juveniles developed faster on cv. Sancho than on cv. Scout. On both pea varieties juvenile mortality was highest at temperatures above 19.6 degrees C and lowest at 19.6 degrees C. Highest cumulative juvenile mortality was recorded on cv. Scout at 26.7 degrees C when only 9% of aphids survived from birth to reproductively mature adults. Fecundity rates were unaffected by temperature in the range tested on cv. Sancho but increased with increasing temperatures between 11.9 and 19.6 degrees C on cv. Scout. These differences in life history parameters were reflected in the population growth (rm) of aphids on both pea cultivars which increased with increasing temperatures between 11.9 and 23.1 degrees C on cv. Sancho and 11.9 and 19.6 degrees C on cv. Scout, declining thereafter. Population growth was consistently greater at all temperatures for aphids reared on cv. Sancho than those reared on cv. Scout.     

不同寄主植物上瓜蚜体内主要构成成分的变化

为揭示寄主植物与瓜蚜Aphis gossypii相互作用的机理, 采用微量凯氏定氮法、索氏提取法、蒽酮比色法、盐酸水解法和气相色谱法分别测定了黄瓜、南瓜、搅瓜、瓢葫芦和哈密瓜等5种寄主植物对瓜蚜体内粗蛋白、脂肪、糖、氨基酸和脂肪酸等主要构成成分的影响。结果表明, 不同寄主植物上瓜蚜体内上述主要构成成分均存在显著差异; 瓜蚜体内主要构成成分以粗蛋白含量最高, 占虫体干重的35.40%~45.25%, 其次为脂肪（24.01%~30.33%）, 最低为总糖（4.09%~7.91%）. 瓜蚜体内含有18种氨基酸, 其中谷氨酸含量最高（5.15~6.97 mg/100 mg）, 其次为天门冬氨酸（3.75~5.33 mg/100 mg）, 再次为亮氨酸（2.59~3.60 mg/100 mg）, 最少为半胱氨酸（0.44~0.49 mg/mg）。瓜蚜体内含有8种脂肪酸。 除瓢葫芦外, 其他4种供试寄主植物上瓜蚜体内棕榈酸含量最高（10.53%~15.55%）, 其次为肉豆蔻酸（3.32%~9.93%）, 亚麻酸含量最低（0.04%~0.17%）。瓢葫芦上瓜蚜体内肉豆蔻酸含量最高, 为16.20%, 其次为棕榈酸（7.15%）。瓜蚜体内饱和脂肪酸含量占虫体干重的20.08%~27.72%, 而不饱和脂肪酸只占2.58%~3.84%。结果提示寄主植物对瓜蚜体内主要构成成分均有显著的影响。     

Biology of Pentalonia nigronervosa (Hemiptera, Aphididae) on banana using different rearing methods

The banana aphid, Pentalonia nigronervosa Coquerel, is present worldwide where banana (Musa spp.) is grown. It is the vector of Banana bunchy top virus (Nanoviridae, Babuvirus), the etiological agent of banana bunchy top disease, currently the most important constraint for banana producers in Hawaii. P. nigronervosa is not well studied, and effects of temperature on its growth and reproduction are unknown. We studied the longevity and fecundity of one clone of banana aphid on different types of plant materials to determine an effective method to study the insect in the laboratory. We found that insects performed better unconfined on plantlets, followed by leaf midrib cuttings. We also conducted complete life table studies with P. nigronervosa on banana leaf midrib cuttings at 20, 25, and 30 degrees C, with a photoperiod of 12:12. Intrinsic rate of increase (r), net reproductive rate (R0), doubling time (DT), nymphal mortality, and mean offspring per female all showed maximal rates at 25 degrees C. Population growth was studied on whole banana plantlets as well, and growth rates were also highest at 25 degrees C. We found r to be greater when aphids were reared on intact banana plantlets than on cuttings. Our results show the importance of comparing insect rearing methods for studies such as life tables.     

A transgenerational interval timer inhibits unseasonal sexual morph production in damson-hop aphid, Phorodon humuli

Abstract.  The induction of sexual and parthenogenetic morphs of the damson-hop aphid, Phorodon humuli , on hops is controlled by daylength. The ability of P. humuli , to produce winged pre-sexual females (gynoparae) in the short-day conditions of spring is inhibited by an interval timer present in generations immediately after hatching of the overwintering egg. The inhibition expires after three generations when nymphs are born and reared in short days (LD 12 : 12 h), irrespective of whether their parents are reared in short or long days (LD 18 : 6 h). No gynoparae are produced by aphids maintained for 13 generations in long days. Two wingless aphids from 35 survive transfer from Prunus spinosa to hops. No winged females are produced during nine generations among their progeny maintained in long days on hops, but gynoparae, followed by males, are produced one generation after these aphids are transferred to short days.     

Effect of temperature and host stage on performance of Aphelinus varipes Förster (Hym., Aphelinidae) parasitizing the cotton aphid, Aphis gossypii Glover (Hom., Aphididae)

Development time, mummification, pupal mortality, host feeding and sex ratio of a Norwegian strain of Aphelinus varipes Förster parasitizing the cotton aphid, Aphis gossypii Glover were studied at 20, 25 and 30°C in controlled climate cabinets. Petri dishes with cucumber ( Cucumis sativus L) leaves on agar were used as experimental units. Cotton aphids in different larval instars and as adults, reared at the three different temperatures, were presented to A. varipes in a `no-choice' situation for 6 h. These presentations were done at 25°C in each experiment to avoid an influence of temperature on parasitization rate. More first instar aphids were parasitized than third and fourth instars among the aphids reared at 20°C. Pupal mortality of the parasitoid was not influenced by temperature. It was lower in aphids parasitized as adults than in aphids parasitized in second instar. The sex ratio of A. varipes was female-biased, and varied between 92% females developed from aphids reared at 25°C and 70% from aphids reared at 20°C. The sex ratio was not significantly influenced by host stage. The development time of A. varipes ranged from 17.5 days at 20°C to 9.8 days at 30°C.     

Life history traits of Aphis gossypii Glover (Hom., Aphididae) reared on four widely distributed weeds

Variation in the life history traits of cotton aphids, Aphis gossypii Glover, reared on four widely distributed weeds, Ageratum houstonianum Mill., Bidens pilosa L. var. radiata Sch. Bip., Solanum nigrum L. and Spermacoce latifolia Aubl., were investigated. Cotton aphids were reared in the laboratory at 25°C. Each host plant had a distinct effect on aphid life history traits. Cotton aphids reared on S. nigrum had a significantly shorter developmental period, and age-specific fecundity peaked early. In contrast, cotton aphids reared on S. latifolia had a long developmental period and low age-specific fecundity. Cotton aphids that fed on B. pilosa and A. houstonianum displayed intermediate rates of growth and age-specific fecundity. Because the curves of age-specific fecundity ( m_x ) and age-specific net maternity ( l_x  m _x ) on each host plant were close together, development time and the pattern of age-specific fecundity were the major factors determining the population growth potential of the cotton aphid on each weed. As a result, the intrinsic rate of population growth for aphids reared on S. nigrum was significantly higher ( r_m =0.527 ± 0.011) than it was for aphids reared on S. latifolia ( r_m =0.194 ± 0.012).     

Temperature and plant nutrient effects on the development, survival and reproduction of Cinara sp. nov., an invasive pest of cypress trees in Africa

Cinara sp. nov., previously identified as Cinara cupressi (Buckton) (Homoptera: Aphididae), is an important alien aphid pest of cypresses and junipers, and invaded Africa in the late 1980s. The work reported here was carried out as part of a larger programme aimed at the classical biological control of the aphid in Africa. Basic life history attributes including life table statistics of the aphid were quantified in order to facilitate the development of efficient aphid culturing methods and essential baseline information necessary for the culturing of potential parasitoid biological agents prior to selection for introduction to Africa. Developmental rates and fecundity were studied under four constant temperatures (10 °C, 15 °C, 20 °C, and 25 °C). The effects of several plant nutrients (nitrogen, potassium and phosphorus) supplied at different dose levels on life history attributes of Cinara sp. nov. were also studied.Unlike most other aphids, the apterous morph of Cinara sp. nov. developed through only three instars, and the alate four instars. The aphid is highly aggregative and exploits a wide range of feeding sites from young green branches to woody stems. The developmental period of Cinara sp. nov. ranged from 9.3 days at 25 °C to 22.3 days at 10 °C and the developmental threshold was 0.61 °C. Reproduction was delayed, because of the longer duration of development, and nymph production decreased with decreasing temperature. The intrinsic rate of increase ranged between 0.117 at 25 °C and 0.060 at 10 °C. Aphid size increased significantly as temperature was lowered. Wing formation was not induced when apterae were reared for up to three generations at each constant temperature but continuous crowding in the supply cultures held at 21 °C resulted in a high number of alates being formed. No appreciable effects of the different plant nutrients, supplied either singly or in combination, on the duration of instars or overall survival could be detected.     

Relative suitability of crested wheatgrass and other perennial grass hosts for the Russian wheat aphid (Homoptera: Aphididae)

The Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphididae), reproduces parthenogenetically in North America and must survive year-round on host plants, including in late summer when small grains are not in cultivation. During this time, cool-season perennial wheatgrasses (Poaceae: Triticeae) contribute substantially to aphid survival, crested wheatgrass (Agropyron spp.) particularly. In greenhouse studies, the number of aphids per plant was measured after four infestation periods on unvernalized and vernalized wheatgrasses. Before placement on these test plant species, aphids were reared either on winter wheat or on the grass host species on which aphid progeny were counted. On vernalized plants, aphids reared on wheat resulted in more aphids per test plant than when the aphids were reared on wheatgrasses, but on unvernalized plants the number of aphids per test plant did not differ significantly regardless of rearing host. Aphids on crested wheatgrass were similar in number to the other grasses when plants were unvernalized. However, when plants were vernalized, crested wheatgrass supported significantly more aphids than some of the other hosts. Aphid numbers increased on all test species as infestation period lengthened, and plant growth was largely unaffected by aphid feeding. These results suggest if sufficient moisture is available during summer when small grains are not in cultivation, all host species observed are capable of sustaining aphids. Crested wheatgrass is an abundant and important host of the Russian wheat aphid in its northern range of the western United States, but other less prevalent wheatgrasses also may contribute to aphid survival during late summer when small grains are not in cultivation.     

Precocious metamorphosis and wing formation in the pea aphid,Acyrthosiphon pisum,induced by precocene analogue 7-ethoxy-6-methoxy-2,2-dimethylchromene

Maternal treatment with 5 μg of the precocene analogue 7-ethoxy-6-methoxy-2,2-dimethylchromene influenced offspring development in the pea aphid, Acyrthosiphon pisum. Under conditions favoring the production of apterous offspring, virginoparous aphids produced a significant proportion of alates and precocious adultoids; the precocious adultoids were sterile. The effect of precocene on offspring development was temporary. Some implications of precocene treatment for aphid control are discussed.     

Lipid composition of the pea aphid,Acyrthosiphon pisum (Harris) (homoptera: Aphididae), reared on host plant and on artificial media

Polar and neutral lipids and their constitutive fatty acids were quantified in the pea aphid, Acyrthosiphon pisum (Harris), grown on host plant or on a lipid free artificial diet. The results were compared to determine if lipids were involved in the suitability of the diet for continuous rearing of this A. pisum biotype. For apterous adults grown on plants, the lipids were characterized by a low amount of neutral lipids (2.5% weight/fresh weight) almost entirely (96.4%) composed of hexanoyl and sorboyl dimyristin. These storage lipids were higher in the alatae (3.8%), probably correlated with potential flight activity. The phospholipid amounts were identical in these two morphs (1.3–1.4% weight/fresh weight), comprised mainly of phosphatidylethanolamines (52%) and phosphatidylcholines (40.6%). These phospholipids contained a still unidentified fatty acid, with a retention time close to that of linolenic acid and synthesized by the aphid or its bacterial symbionts (not found in plants). The apterous adult aphids reared on an artificial diet showed an accumulation of neutral lipids (8.9% for the first generation); this increase was shown to be slightly greater for the hexanoyl and sorboyl triglycerides. In contrast, the phospholipids decreased in aphids reared on an artificial diet (1.1% and 0.9%, respectively, for first and second generation), correlated with a phospholipid fatty acid profile significantly deficient in C18:3 and in the unidentified peculiar fatty acid. These phospholipids are essential components of biological membranes and a diet-driven deficient synthesis in some of their components may result in the observed symptoms. © 1992 Wiley-Liss, Inc.     

Continuous rearing of the aster leafhopper, Macrosteles fascifrons, on a chemically defined diet

A holidic diet for feeding the aster leafhopper, Macrosteles fascifrons, was formulated. The amino acids, B-vitamins, and sucrose are less concentrated than in aphid diets. Cholesterol, at 5 mg/ml, is required for the last ecdysis. Although leafhoppers reared on this diet have poorer survival and shorter life span than those reared on plants, they produce more progeny. Leafhoppers reared on this diet have completed the ninth generation and the culture is still thriving.     

Fitness effects of two facultative endosymbiotic bacteria on the pea aphid,Acyrthosiphon pisum,and the blue alfalfa aphid,A. kondoi

The effects of two bacterial endosymbionts, designated PASS and PAR, were evaluated on the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera:Aphididae), in which they occur facultatively, and on the blue alfalfa aphid, A. kondoi Shinji, in which these bacteria have not been found in natural populations. Subclones of pea aphids and blue alfalfa aphids, derived from parent aphid clones that did not contain PASS or PAR, were infected with one or both bacteria, generating PASS- and/or PAR-positive subclones with minimal genetic differences from the parent clones. Under laboratory conditions at 20 °C, PAR consistently reduced the fecundity (by between 19 and 60%) of subclones derived from three different parent pea aphid clones on bur clover, Medicago hispida Gaertn. PAR had intermediate effects on pea aphids reared on sweet pea, Lathyrus odoratus L., and had no significant effect on pea aphids on alfalfa, Medicago sativa L. The effect of PASS was either neutral or negative, depending on parent clone as well as host plant. Also at 20 °C, PASS reduced fecundity (70–77%) and longevity (40–48%), and increased the age of first reproduction (by up to 1.5 days) of blue alfalfa aphid reared on alfalfa and clover. PAR had a less dramatic effect (e.g., 30–39% reduction in fecundity) on these traits of blue alfalfa aphid. In contrast, PAR and PASS increased the fitness of pea aphid subclones of one parent clone reared for three generations at 25 °C on each of the three test plants. Without facultative bacteria, fecundity of the parent clone was reduced to a mean total of < 6 offspring per adult at this elevated temperature, but with PASS or PAR, mean total fecundity of its subclones was > 35. However, this ameliorative effect of facultative bacteria at 25 °C was not found for two other sets of parent clones and their derived subclones. Alate production in pea aphids was significantly increased in large populations of two PASS- and PAR-positive subclones relative to their parent clones. Attempts to transmit PASS or PAR horizontally, i.e., from aphid to aphid via feeding on host plants (bur clover), were unsuccessful.     

Influence of host plant on growth and reproduction of Aphis nerii and feeding and prey utilization of its predator Menochilus sexmaculatus

Influence of different physiological stages (young, mature and senescent) of Calotropis gigantea leaves on growth and reproductive ability of A. nerii and feeding, prey utilization, fecundity and lipid content of its predator M. sexmaculatus were investigated. Increased reproductive period, total life span and reproduction of nymphs per female of A. nerii were observed when reared on mature leaves. This relative preference of A. nerii and maximum utilization of mature leaves as compared to other physiological aged leaves are mainly due to changes in the chemical composition such as protein, carbohydrate, lipid, amino acid, nitrogen and phenolic of C. gigantea. Further, aphids reared on mature leaves influenced its predator's (M. sexmaculatus) growth, prey utilization and reproductive performances. Fecundity and longevity were high, while developmental time of predator was shorter on mature leaves fed aphid. Maximum prey utilization and increased efficiency of ingested and digested food of predator was observed on mature leaves reared aphid. The results are interpreted and discussed in relation to plant aphid and predator interaction (tritrophic).