Host-selection behaviour by genetically identical aphids with different plant preferences

The behaviour of summer and autumn winged forms of the black bean aphid, Aphis fabae Scopoli (Homoptera: Aphididae), was compared on two plants utilized at different stages of the insect’s life cycle. Adult autumn migrants (gynoparae) are monophagous, colonizing spindle (Euonymus europaeus), whereas polyphagous summer winged aphids (alate virginoparae) are associated with a variety of herbaceous plants, including broad bean (Vicia faba). When aphids from a single clone were given access to a spindle leaf and a bean seedling in choice tests, many virginoparae settled and larviposited on both plant species over 24 h. By contrast, gynoparae showed a clear preference for spindle, with 93.5% of settled adults and 98.3% of larvae on this plant species. Close‐up video monitoring showed that gynoparae discriminated beans from spindle within a 5‐min period, whereas virginoparae behaved similarly on both plant species. For gynoparae, the major behavioural difference on the two plants appeared after a brief (epidermal) stylet penetration, with many insects taking flight within a few seconds of stylet withdrawal from bean. Factors detected during stylet insertion by gynoparae must therefore inhibit take‐off on spindle. Electrical recording experiments showed that aphids often punctured a cell membrane during brief probes on both plant species, and intracellular stylet activities always included a waveform associated with ingestion. When gynoparae puncture spindle cells their behaviour is probably modified by intracellular metabolites detected via gustation of ingested epidermal cell sap. These cues may inhibit the take‐off reflex which otherwise follows probing.     

Chemical aspects of host‐acceptance behaviour in the bird cherry‐oat aphid Rhopalosiphum padi: host‐acceptance signals used by different morphs with the same genotype

Host acceptance by gynoparae and winged virginoparae of the bird cherry‐oat aphid Rhopalosiphum padi (L.) is investigated utilizing leaves and aqueous extracts of the primary and secondary hosts, as well as nonhost plants. Gynoparae are specialized to reproduce on bird cherry Prunus padus L., whereas virginoparae reproduce and feed on various grasses. Host acceptance is assessed using levels of reproduction and survival for adults, as well as survival for nymphs. Little is known of host acceptance by nymphs. The data show that gynoparae and winged virginoparae produce nymphs almost exclusively on their host plants, bird cherry and barley leaves, respectively, over 72 h. When tested with aqueous plant extracts, however, gynoparae produce nymphs almost exclusively on bird cherry extract and progeny numbers are found to be similar to those on plant leaves. Few nymphs are produced on artificial diet. By contrast, winged virginoparae produce nymphs on aqueous extracts of barley, bird cherry and bean, as well as on artificial diet. The numbers of nymphs deposited by gynoparae are similar on aqueous extracts of bird cherry leaves collected at different times during the growing season. When extracts from leaves of various Prunus species are tested, only leaves of P. padus and Prunus virginiana stimulate parturition. Oviparae, the sexual female nymphs of gynoparae, survive well for 96 h on both bird cherry and barley leaves but not on bean seedlings, whereas nymphs of winged virginoparae survive well only on barley leaves. They do not survive for 96 h on any plant‐leaf extracts, although they do survive on artificial diet.     

Maternal reproductive decisions are independent of feeding in the black bean aphid,Aphis fabae

Aphids are phloem feeders and an important assumption has been that reproduction is initiated only after phloem ingestion. Here we investigate the plant tissue location of parturition cues in winged and wingless, summer virginoparae and autumn migrants (gynoparae) of the black bean aphid, Aphis fabae. These seasonal forms have different host preferences. Using electrical penetration graph (EPG: to observe activity of the mouthparts) and video-monitoring procedures we demonstrate that the time to first parturition after host-plant contact is significantly shorter than the time to first registered phloem contact in the summer winged form. In gynoparae, the time to first parturition does not significantly differ from time to first phloem contact but is shorter than time to first phloem ingestion. Times to first parturition, first registered phloem contact and first phloem ingestion do not differ significantly in the summer wingless form. Simultaneous EPG and video recording procedures show that a high proportion of individuals of all morphs (45-70%) initiate reproduction before sustained phloem activities (salivation/ingestion). The only behaviours that all individuals demonstrate before first parturition are ‘non-penetration’ (aphid on plant surface with mouthparts outside plant) and stylet ‘pathway activity’, including secretion of gelling saliva and penetration of the non-vascular (epidermis and mesophyll) cells. A short period of penetration of the peripheral plant tissues (five cell punctures per individual) by aphids tethered and monitored by EPG decreases the time to first parturition of the winged summer form when subsequently placed on a Parafilm sachet containing 15% sucrose solution. This treatment also significantly increases the incidence of reproduction and individual reproductive output of gynoparae over a 24-h period. No detectable effects of tissue penetration on subsequent reproductive output are observed in the wingless summer form. Additionally, EPGs reveal that a number of aphids of all morphs display xylem ingestion, which occurs predominantly before initiation of phloem feeding but is not necessary to initiate parturition. It is concluded that aphids are likely to detect parturition cues during stylet punctures of cells within peripheral tissue layers, before reaching the phloem vessels.     

Host acceptance by aphids: probing and larviposition behaviour of the bird cherry-oat aphid, Rhopalosiphum padi on host and non-host plants

The probing and larviposition behaviour of the bird cherry-oat aphid, Rhopalosiphum padi on summer and winter host plants were investigated using electrical penetration graph (EPG) coupled with simultaneous video recording. In this way the precise probing history prior to parturition can be monitored and the location of possible reproductive stimulants identified. On the host plant, all gynoparae (autumn winged females that give birth to sexual females on bird cherry, Prunus padus, the primary host) and 55% of winged virginoparae (summer females which produce further virginoparae on barley, Hordeum vulgare, a secondary host) initiated larviposition before phloem contact. However, 90% of wingless virginoparae (on barley) contacted the phloem before first larviposition whilst 10% did not. Thus, phloem contact does not appear to be a pre-requisite for these aphid forms to initiate reproduction.     

Reproduction and probing behaviour of the bird cherry‐oat aphid Rhopalosiphum padi on detached leaves and leaves on intact seedlings of the winter host,bird cherry Prunus padus

Video recording and electrical penetration graph techniques are used simultaneously to investigate host acceptance (in terms of reproduction) and probing activities of autumn migrants (gynoparae) of the bird cherry‐oat aphid Rhopalosiphum padi (L.) on detached leaves and on leaves on intact plants of the winter host, bird cherry Prunus padus. There are no significant differences between the times taken to first parturition or the number of nymphs produced over a 6‐ or 18‐h period on intact plants or detached leaves. Stylet probing activities (i.e. total probe duration, xylem ingestion, the time to first phloem contact and phloem salivation) are also similar in the two situations.     

HOST ALTERNATION IN APHIS FABAE SCOP.

Experiments on the feeding preferences and relative fecundity of Aphis fabae among leaves of different ages and kinds were extended to the comparison of different forms of the aphid: apterous and alate virginoparae and gynoparae.
All three forms showed a preference for the primary host, Euonymus , over a secondary host, sugar beet, but this preference was strongest in the gynoparae, weaker in the alate virginoparae and weakest in the apterae. The relative fecundity of the aphids on the two kinds of leaf paralleled their feeding preferences most closely in the gynoparae, less so in the alate virginoparae and least in the apterae.
All three forms also showed some preference for growing over mature leaves of the same kind, but this preference was strongest in the apterous virginoparae, weaker in the alate virginoparae and weakest in the gynoparae. The relative fecundity of the aphids on the two ages of leaf paralleled their feeding preferences most closely in the apterae, less so in the alate virginoparae and least in the gynoparae.
The physiological, ecological and evolutionary significance of the results is discussed in the light of the dual discrimination theory of aphid host selection.     

Responses of holocyclic and anholocyclic Rhopalosiphum padi populations to low‐temperature and short‐photoperiod induction

The different life cycles of aphid species make these organisms good models for studying the short‐term consequences of sex. The bird cherry‐oat aphid Rhopalosiphum padi has a wide geographic distribution and correspondingly different life cycles. In this study, the life cycles of R. padi collected from six different regions in China were characterized experimentally by comparing the responses of holocyclic and anholocyclic populations to low‐temperature and short‐photoperiod induction. Clones collected from Chuzhou, Taian, and Taigu consistently reproduced via obligate parthenogenesis, whereas clones from Hami and Baicheng were holocyclic in their response, and those from Lanzhou were both holocyclic and anholocyclic. Prolonged exposure to low temperature and a short photoperiod (LS) had negative effects on the offspring of anholocyclic aphids with regard to adult lifespan, total longevity, and fecundity compared with aphids maintained at a normal temperature and a long photoperiod (NL). Holocyclic LS R. padi had longer developmental times at all nymph stages, a shorter adult lifespan, shorter total longevity, and a lower fecundity than NL counterparts. The adult prereproduction period of gynoparae was significantly longer than that of virginoparae, and the total longevity of gynoparae was significantly shorter than that of virginoparae. Moreover, the net reproductive and gross reproduction rates, as well as the total fecundity, were roughly fivefold higher in virginoparae than in gynoparae, indicating that there is the short‐term cost of sex. When maintained on their secondary host (Triticum aestivum), gynoparae, males, and oviparae produced by holocyclic populations could survive, and gynoparae produced oviparae. However, under NL conditions, oviparae could not produce overwintering eggs on the secondary host, whereas a few overwintering eggs were generated by oviparae under LS conditions. Taken together, these results illuminate the complexity of insect responses and contribute to a complete understanding of the aphid life cycle and its evolution.     

Electroantennogram and behavioural responses of different forms of the bird cherry-oat aphid,Rhopalosiphum padi,to sex pheromone and a plant volatile

Winged (alate) virginoparae were induced in the laboratory by crowding the bird cherry-oat aphid, Rhopalosiphum padi (L.) under long-day conditions. Males and gynoparae (the winged female form that produces sexual females) were induced by short days. Electroantennogram (EAG) and behavioural responses were investigated in each of the three forms to two aphid sex pheromone components, (-)-(4aS,7S,7aR)-nepetalactol and (+)-(4aS,7S,7aR)-nepetalactone, and benzaldehyde, a volatile which is released by the winter host plant. All three compounds elicited EAG responses with the males showing the highest sensitivity to each compound. Both the nepetalactol and the nepetalactone elicited larger EAG responses in gynoparae than in the winged virginoparae but antennae from virginoparae were more responsive to benzaldehyde. Although the nepetalactone is not a sex pheromone component in R. padi the EAG responses were similar to those evoked by the nepetalactol, the sex pheromone, in all three aphid forms. In a linear-track olfactometer, significantly more male R. padi moved into air containing nepetalactol, nepetalactone or benzaldehyde than into a simultaneous choice of clean air (i.e. attraction) but nepetalactol was more attractive than nepetalactone. Males, however, showed no response to a mixture of nepetalactol and nepetalactone. Gynoparae were attracted only to the nepetalactol but were less sensitive than the males and showed no response to the nepetalactone or benzaldehyde. In contrast, alate virginoparae showed no behavioural responses to any of the compounds. The present study supports the idea that the male R. padi utilise both sex pheromone and benzaldehyde for mate/host-plant location in autumn. It also demonstrates, for the first time, polyphenic differences in the olfactory responses at the peripheral level between the two female forms. Such differences impact on the life-cycle strategy where winged virginoparae move between graminaceous summer host plants while gynoparae move from the summer hosts to the bird cherry, winter host. The latter move appears to be assisted by the sex pheromone released by sexual females, already present on that host, acting as an aggregation pheromone.     

Feeding responses of an oligophagous bean aphid, Megoura crassicauda, to primary and secondary substances in Vicia angustifolia

The feeding behaviour of the aphid Megoura crassicauda Mordivilko (Homoptera: Aphididae), which feeds selectively on plants in the genus Vicia (Fabaceae), was studied. The aphids deposited proteinaceous stylet sheaths intercellularly towards the phloem tissues of host plants. Similar stylet sheaths were formed on a Parafilm membrane when host‐specific acylated flavonoid glycosides [two 2″‐O‐(E)‐p‐coumaroyl esters of quercetin 3‐O‐diglycosides] present in the extracts of the narrow vetch, Vicia angustifolia L., were supplied in the solution covered by the membrane. In contrast, their corresponding deacyl analogues, present more abundantly in the host plant tissues, were not stimulatory, which suggested specificity in the structural requirements of the probing stimulants. While the aphids imbibed an artificial diet composed of primary nutrients (e.g., sucrose and amino acids) and produced a large quantity of honeydew, acylated flavonoids alone and non‐acylated flavonoids supplied with the nutrients more or less suppressed honeydew production. These findings implied that the acylated flavonoids serve as a cue to navigate the stylet sheath towards the phloem prior to sap‐sucking, whereas non‐acylated flavonoids may serve as a negative stimulus to refrain from sucking during tissue penetration before tapping the phloem, although the distribution of these compounds in the plant tissues remains unknown. Thus, the feeding behaviour of M. crassicauda appears to be controlled by multiple chemical stimuli in the process of the settling on its host plant.     

Wing development and parthenogenesis induced in progenies of kinoprene-treated gynoparae of Aphis fabae and Myzus persicae

Presumptive gynoparae of Aphis fabae and Myzus persicae were exposed to various levels of kinoprene (Zoecon's ZR 777) by being placed as 4th-instar alatiform larvae on bean or radish seedlings that had been sprayed with different concentrations of kinoprene in an acetone-tween-water emulsion. Larvae exposed to the highest (0.1%) concentration tested developed into adults 1 to 2 days sooner than those on control plants. The adults on the treated plants had variously deformed wings, reduced sclerotization (and pigmentation in the case of M. persicae) and other apteriform features. On reaching adulthood the affected aphids settled to feed and started to larviposit some days earlier than the control aphids. After two weeks as adults, treated gynoparae of M. persicae produced more larvae than the 7 to 9 typically deposited by control gynoparae under the short-day and cool temperature conditions employed in these tests.Whereas most or all of the larvae produced by the control gynoparae developed into oviparae (apterous, egg-laying, sexual females), gynoparae exposed to 0.1% kinoprene-treated plants predominantly produced alatiform viviparous offspring. If the latter were allowed to develop on untreated plants they deposited a few oviparous larvae. Alatiform virginoparae of M. persicae (from the same holocyclic strain that produced the gynoparae) also responded to kinoprene by developing wing deformities and by producing alatiform offspring. In contrast, alatiform virginoparae from an androcyclic strain of M. persicae, although developing wing deformities, produced only apterous progeny.The stimulation by kinoprene of wing development and parthenogenesis in the progeny of treated gynoparae is discussed in the light of our present knowledge of these aspects of aphid polymorphism.     

A morphological study on autumnal morphs of Aphis glycines (Hemiptera: Aphididae)

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is one of the most important pests of soybean. The complex life cycle of A. glycines is characterized as heteroecious and holocyclic, and has seasonal polymorphisms occurring during its life cycle. In the autumn, A. glycines occur as winged and wingless virginoparae in soybeans, as gynoparae and males that migrate from soybeans to Rhamnus spp. and as gynoparae, males and oviparae on Rhamnus spp. In this study, wingless virginoparae, gynoparae, males and oviparae of A. glycines were successfully induced in the laboratory and morphological parameters of these morphs were selected for quantitation. To aid in identification of these A. glycines autumnal morphs, these aphids were imaged by microscope and significant differences in morphological characteristics were found: distal parts of hind leg femurs of gynoparae were grayish black, which were darker than those of winged virginoparae; the 4th instars of gynoparae, males and winged virginoparae differ greatly in dorsal abdomen coloration and covering. Our results provide an important guide for distinguishing adults of gynoparae and winged virginoparae, and for identifying nymphs of gynoparae, males and winged virginoparae.     

Electroantennogram responses of aphid nymphs to plant volatiles

Abstract. Electroantennogram (EAG) responses of immature aphids were investigated for 30 plant volatile compounds in third‐ and fourth‐stadium nymphs of the black bean aphid, Aphis fabae. The nymphs were destined to develop into adult alate (winged) virginoparae. The EAG response profiles were similar to those previously reported in the adults. Among the compounds tested, hexanonitrile elicited the largest EAG responses in both nymphal stadia, corresponding to previously reported results with adults. Six‐carbon aliphatic compounds showed relatively higher EAG activities in the nymphs but, in contrast, (E)‐2‐hexenal, benzaldehyde, α‐pinene and β‐pinene, and citronellal elicited relatively smaller EAG responses in nymphs than adults. Although overall EAG response profiles were similar between the third and the fourth stadia for the majority of the volatiles, four aldehyde compounds, hexanal (E)‐2‐heptenal, 2‐hydroxybenzaldehyde and citronellal, showed relatively higher EAG activities in the third than in the fourth stadium. The present study indicates that aphid nymphs possess a functional olfactory receptor system before the antennae are fully developed morphologically and physiologically.     

Winter Host Plant Specialization in a Host-Alternating Aphid

The host alternating aphid, Rhopalosiphum padi (L.), feeds in summer on several different species of grasses but is monophagous on its winter host, Prunus padus L. The monophagy on P. padus could be a result of the restricted host range of the several different generations colonizing, or feeding, on this host during autumn–winter–spring. This study shows that the winter host plant specificity of R. padi is controlled mainly by the preference of the females remigrating (gynoparae) to the winter host, P. padus, in autumn. The other generations living on the winter host, i.e., sexual females, males, and spring generations, all accept a broader range of winter hosts. One alternative host plant, Prunus spinosa L., could be utilized by all generations associated with the winter host, except for the females remigrating at autumn.     

Host plant influences pathogenicity of Beauveria bassiana to Bemisia tabaci and its sporulation on cadavers

Laboratory bioassays were conducted to determine host plant effect on pathogenicity of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuill. (Ascomycota: Hypocreales) to the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Fourth instar B. tabaci reared on cucumber, tomato, melon, green pepper, potato, eggplant, marrow, cabbage, bean or cotton, were treated with 1 × 10⁷ conidia/ml B. bassiana EABb 93/14-Tp isolate. Mortality caused by B. bassiana significantly increased with time and it was significantly affected by the host plant on which the nymphs were reared. Mean mortality of nymphs 8 days after inoculation ranged between 52.3±7.3 for nymphs reared on cotton and 91.8±5.8 for nymphs reared on cucumber. Average survival times of nymphs treated with the fungal suspensions were also significantly influenced by the host plant, with a mean of 4.7±0.1 days for nymphs reared on cucumber, 6.6±0.2 days for cotton and 6.9±0.1 days for green pepper. The production of newly formed conidia was also affected by host plant and varied from 111000±8600 conidia/cadaver for nymphs reared on cotton to 597000±28000 conidia/cadaver for those reared on melon.     

Embryogenesis and oögenesis in alate virginoparae,gynoparae, and oviparae of the aphid Myzus persicae, in relation to photoperiod

The study reports on the effects of prenatal and/or postnatal exposures to short-night or long-night conditions, and of crowding, on embryogenesis and oögenesis in alate virginoparae, gynoparae, and oviparae of a holocyclic strain of the green peach aphid, Myzus persicae, from Yakima, Washington State.In alate virginoparae raised at a density of 10–20 per radish seedling in a short-night regime (8 hr darkness per diem), 3–4 embryos occurred in each of their 10 ovarioles, when the aphids attained adulthood. More than 30 larvae were deposited by most of these alatae. However, in young adult gynoparae, raised at these densities in a long-night regime (15 hr darkness per diem), only one viable embryo (a presumptive ovipara) occurred per ovariole. The follicle containing this embryo was followed by 1–2 abnormal follicles in each ovariole, and the number of larvae deposited by a gynopara was generally less than 10. In young adult oviparae similarly raised under a long-night regime, only one egg typically occurred in each of their 10 ovarioles, and the eggs deposited by an ovipara (only after it had mated) generally numbered less than 10. Alate virginoparae and gynoparae contained an additional embryo in some of their ovarioles when these morphs were raised at a lower density (1–5 per plant).Presumptive gynoparae partially developed the reproductive features of alate virginoparae when transferred to a short-night regime at birth; the converse was true when presumptive alate virginoparae were transferred to a long-night regime early in larval life. Oviparae maintained in short nights from before birth developed the appearance of apterous virginoparae but still produced eggs rather than embryos. However, their oögenesis was enhanced and eggs (10–20) were deposited by them without prior mating. Under all regimes tested, oviparae were always deposited early in the larviposition sequence of their alate mothers, and the number of oviparae deposited never exceeded 15.The possible involvement of juvenile hormone in the regulation of these events and the ecological significance of the results are discussed.     

The effect of juvenile hormone on host-plant preference in the black bean aphid, Aphis fabae

ABSTRACT. When offered the choice between a germinating tick bean (summer host) and a detached spindle leaf (winter host) adult gynoparae of Aphis fabae Scop. showed a distinct preference for spindle, as judged by site of larviposition. However, when offered the same alternatives, all four larval instars showed a settling preference for bean. A switch in host preference therefore occurs at or shortly after final (fourth) moult. Fifth instar, supernumerary larvae induced by juvenile hormone (JH I) treatment also preferred bean, indicating that the host preference switch at the fourth moult had been inhibited. Larval/adult intermediate forms produced by JH I treatment, but which were capable of parturition, showed a significant increase in the acceptability of bean as a larviposition site. Acceptability was proportional to the degree of juvenilization. Thus, although larviposition is an adult prerogative, JH I can influence the preferred site. This may, however, be an indirect effect which reflects a juvenilized settling preference.     

Aphids secrete watery saliva into plant tissues from the onset of stylet penetration

Aphid feeding requires the secretion of two types of saliva: gelling saliva (from the principal gland) that forms an intercellular sheath for the penetrating stylet, and watery saliva [from accessory salivary glands (ASGs)] that facilitates intracellular penetration and phloem feeding. Plant viruses can be used as salivary markers to investigate key steps in aphid feeding, and penetration can be monitored electrically using the electrical penetration graph (EPG) approach. We conducted a series of EPG‐controlled transmission experiments using Cucurbit aphid‐borne yellows virus [CABYV; Polerovirus spec. (Luteoviridae)], which is retained in the ASGs, as a marker for watery saliva secretions. The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), was used as a vector and melon seedlings, Cucumis melo L. (Cucurbitaceae), as host plants. Viruliferous aphids were interrupted at various stages during stylet penetration, i.e., during intercellular penetration prior to intracellular puncture and following a potential drop within the first probe. Viruliferous aphids and leaf disc samples obtained from the stylet penetration site were used to detect CABYV by quantitative real‐time RT‐PCR. Approximately half of the inoculated leaf discs were found to be infected with CABYV after very brief (12.9 ± 1.9 s) intercellular stylet probes and before intracellular stylet puncture. The number of virus particles ejected during such probes was similar to the number ejected by aphids during longer probes including a single intracellular puncture. Our results therefore suggest that watery saliva is secreted by aphids from the onset of stylet penetration.     

Lipid composition in long-day and short-day forms of the black bean aphid,Aphis fabae

Long-day reared winged (alate) virginoparae from laboratory stock cultures which had been reared throughout larval development on bean stipules were significantly smaller (0.46+/-0.02 mg; mean+/-SEM) than short-day-reared gynoparae (0.69+/-0.04 mg; the winged autumn migrant) which completed development on intact beans. When winged virginoparae were raised from the third stadium on bean seedlings they grew larger (0.86+/-0.02 mg) but the gynoparae contained proportionally more total lipid (12.1+/-0.4%, gynoparae; 7.4+/-0.6%, stipule-reared virginoparae; 9.2+/-0.8%, seedling-reared virginoparae). Wingless aphids (apterae) were heavier, whether reared in short (0.99+/-0.03 mg) or long days (0.95+/-0.04 mg) but the lipid content was low (4.5+/-0.7% and 4.9+/-0.6%, respectively). The triacyl-, diacylglycerol and the phospholipid contents followed this trend but analysis of the fatty acid moieties of the triacylglycerides showed phenotypic differences. The ratios of myristic acid:palmitic acid were significantly higher in the winged forms than the wingless forms and were much higher in the gynoparae than the winged virginoparae. Short-day-reared wingless females also had a higher myristic acid:palmitic acid ratio than long-day-reared apterae, possibly reflecting the embryonic gynoparae maturing in their ovaries.     

Behavioural differences during host selection between alate virginoparae of generalist and tobacco-specialist Myzus persicae

Host plant selection and acceptance by aphids involves four consecutive steps: (1) prealighting behaviour, (2) leaf surface exploration and probing of subepidermal tissues, (3) deep probing of plant tissues, and (4) evaluation of the phloem sap. Host specialisation in aphids may involve not only different performances on potential hosts, but also different strategies for host selection and acceptance. Myzus persicae s.s. (Sulzer) (Homoptera: Aphididae) is one of the most polyphagous aphid species, although a tobacco‐adapted subspecies, M. persicae nicotianae, has been described. These two taxa constitute a good system for studying the effect of host range on host selection strategies. We studied the first two steps in the host selection process by alate virginoparae of M. persicae s.s. and M. persicae nicotianae on host and non‐host plants, using three types of behavioural assays: wind tunnel, olfactometry, and video‐recording. Alate virginoparae of M. persicae nicotianae recognised and chose their host plant more efficiently than M. persicae s.s., on the basis of olfactory and visual cues, and factors residing at cuticular and subcuticular levels. Host recognition was evident before phloem tissues were contacted. Olfactory cues were apparently not involved in host selection by M. persicae s.s.     

棉蚜寄主专化型及其形成的行为机理

通过生活在甜瓜和棉花上的棉蚜Aphisgossypii Glover的行为,研究棉蚜的寄主专化型及其形成的行为机理。生物学观察显示： 两类棉蚜在寄主植物相互交换以后,定居数显著减少,棉花蚜型棉蚜的繁殖系数及若虫存活率显著下降,说明棉蚜存在甜瓜蚜型和棉花蚜型两种寄主专化型。通过刺探电位技术研究棉蚜的取食行为,以探索其寄主专化型形成的行为机理。结果表明： 甜瓜蚜型棉蚜在棉花上的取食行为容易被中断,但其口针定位韧皮部的能力并没有显著削弱;而棉花蚜型棉蚜在甜瓜上的取食行为受到更大的影响,口针无法顺利定位至韧皮部,并在2 h内根本无法在筛管内取食。生物学观察和EPG取食行为分析都显示： 与甜瓜蚜型棉蚜相比,棉花蚜型棉蚜对寄主的要求更严格-寄主专化程度更高,对寄主的利用率更高。