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Aphid Predator (Coleoptera: Coccinellidae)Coccinella septempunctataSeven-spot ladybirdOn this page: Identification & Distribution Biological Control of Aphids Classical biological control in North America How effective was control? Adverse effects of introduction Augmentative releases Integrated control & conservation biological control Modelling studies Biology and Ecology Feeding behaviour Host-finding behaviour Competition between predators/parasitoidsIdentification & DistributionCoccinella septempunctata is a fairly large ladybird (5.2-8.6 mm), oval in shape and strongly convex. The head is black with a pair of semicircular white frontal spots, one on either side of the inner margin of the eyes. The pronotum is black, with a pale yellow or white antereolateral spot. The ground colour of the elytra is usually red or orange (see first two pictures below), rarely yellow. The typical elytral pattern is seven black spots: there is one common spot around the scutellum, and three on each elytron with small white patches on either side of the scutellum, just above the scutellar spot. The size of the spots is highly variable. The underside of Coccinella septempunctata is more or less completely black.
The fourth instar larva of Coccinella septempunctata (see third picture above) is dark grey-black with mostly black tubercles. The sides of the meso- and metathorax are pale grey, but there are orange lateral patches on the prothorax (cf. Coccinella undecimpunctata which lacks the orange lateral patches on the prothorax). The dorso-lateral and ventro-lateral tubercles on abdominal segments one and four are orange. Coccinella septempunctata is a common species occurring in many different habitats including gardens, grassland, and broad-leaved and mixed forests. The seven-spot ladybird is mainly aphidophagous, but also feeds on thrips (Thysanoptera), white flies (Aleyrodidae) and the eggs and larvae of other insects. There are one or two generations a year. The adults overwinter in sheltered sites often in large aggregations.Coccinella septempunctata is found throughout Europe, North Africa and most of Asia, and has been introduced to North America and South Africa. Biological Control of AphidsClassical biological control in North AmericaClassical biological control is dependent on two outcomes: First a non-native species has to be introduced to an area, usually by mass release, and then become a self-sustaining population. Second it has to suppress the numbers of an aphid or coccid species well below the level which it formerly reached in the area, ideally below the economic injury level. Several workers have described the rather ad hoc way by which Coccinella septempunctata, then regarded as a highly efficient predator of aphids, was (eventually) successfully introduced into North America. Angalet & Jacques (1975) and Angalet et al. (1979) describe how several attempts were made to establish Coccinella septempunctata in the United States by intermittent releases in various localities in 1956-71. However, no evidence o? permanent establishment was found until June 1973, when several individuals were collected from Hackensack Meadowlands in Bergen County, New Jersey. Investigations in 1974 into the probable origin of this population indicated that there may have been a connection with the refuse from Kennedy Airport and other transport services that is habitually dumped nearby, rather than with the intentional releases of the Coccinellids in previous years. Since that time the species has gone on to colonize every state in the USA, and every province in southern Canada. Schaefer et al. (1987) describe how Coccinella septempunctata, already well established in North America, spread through parts of five Canadian provinces and 34 contiguous eastern states of the United States. In southern coastal Delaware in June 1984, a mass appearance of Coccinella septempunctata occurred where wind systems brought masses of these beetles into the area from unknown sources and dropped them into the seawater. Large numbers then washed up on beaches, and some surviving beetles annoyed vacationers and even bit some people.
Seven-spot ladybirds (Coccinella septempunctata) on Jurmala beach, Latvia, copyright Rulexip under a Creative Commons Attribution-Share Alike 3.0 Unported license A successful introduction - but how effective was the control?The introduction of Coccinella septempunctata certainly was (eventually) highly successful. Hodek & Michaud (2008) focus on the factors that could be responsible for the predominance of Coccinella septempunctata in most habitats of the Palaearctic and for its successful invasion of the Nearctic Region (=North America, Greenland, to northern Mexico). It is polyphagous, but less so than Harmonia axyridis in that it has to eat aphids in order to develop or reproduce. Although the adult size is large, its larvae may be eaten by both Harmonia axyridis and Adalia bipunctata larvae (known as intra-guild predation), but Coccinella septempunctata is not a predator of either species. Although these traits appear to be neutral or negative, many aspects of population plasticity are advantageous for Coccinella septempunctata, often acting in concert with a bet-hedging strategy. Given its high mobility and ability to tolerate a wide range of environments, the inhibition of oviposition in the presence of conspecific larval trails represents an adaptive advantage that favours increased egg dispersal and lowers the risk of offspring mortality due to cannibalism. The ability to temporarily suspend oviposition, combined with heterogeneous voltinism (=brood size, or generations/year) and diapause tendencies, enable a portion of Coccinella septempunctata populations to feed and reproduce on unpredictably occurring aphid populations. An absence of reproductive diapause in males and pre-hibernation mating are other significant adaptations, along with the tendency to produce offspring in excess of the carrying capacity of?local food resources. The authors suggest that one explanation for the broad geographic success of Coccinella septempunctata resides in an ecological plasticity that is based on both genetic and phenotypic (=nongenetic) polymorphisms. Coccinella septempunctata has been reported consuming a wide variety of pest aphids in North America, including the green peach aphid (Myzus persicae), the pea aphid (Acyrthosiphon pisum), the spotted alfalfa aphid (Therioaphis maculata) and potato aphid (Macrosiphum euphorbiae). But, despite the initial optimism, some have argued that ladybirds such as Coccinella septempunctata have never really proved effective in maintaining aphid populations in the field below the level at which they cause economic damage. Kindlmann et al. (2015) noted that the outstanding success of the Australian ladybird beetle, Rodolia cardinalis (see picture below) for controlling the cottony-cushion scale, Icerya purchasi, an important pest of citrus in California, had resulted in the widespread but ultimately inappropriate use of ladybirds as biocontrol agents of aphids rather than for control of scale insects.
Vedalia beetle (Rodolia cardinalis) in Spain, copyright Katja Schulz under a Creative Commons Attribution 2.0 Generic license. Indeed, theory (Kindlmann & Dixon, 1999) predicts that coccid-eating ladybirds (such as Rodolia) which have a developmental rate that is faster or similar to that of their prey are able to reduce the abundance of their prey to greater extent than are aphid-eating ladybirds (such as Coccinella septempunctata), all of which have considerably slower developmental rates than their prey. As a result, aphidophagous ladybirds are likely to be much less effective biocontrol agents than coccidophagous ladybirds. Perhaps ironically, there seems to have been rather little research assessing the ability of Coccinella septempunctata to control aphid pest populations in agriculture, but far more research on the possible adverse effects of its successful introduction in the United States. What were the adverse effects of introduction?Simberloff & Stiling (1996) proposed that Coccinella septempunctata had replaced many native American coccinellid species by competitive displacement. Evans (2000) examined that hypothesis by examining ladybird body size to determine whether there was any evidence for adverse impact on native species, and why the invader had been so successful in establishment. He determined whether mean body size of adults of the five most common native American species, including Hippodamia convergens (see picture below of aggregation), had declined over the period 1991-1997 as Coccinella septempunctata increased rapidly in abundance.
Convergent lady beetle aggregation in California, image copyright John Rusk under a Creative Commons Attribution 2.0 Generic license No such decline was observed for any of those species, thus not providing any evidence that the invader(tm)s establishment had significantly increased scramble competition (=where the resource cannot be monopolized) for food among immature ladybirds. He also compared body size distribution of the invading species with that of native species. The invader was distinctive in having particularly large variation in body size among individuals. Such results are consistent with the hypothesis that the invader(tm)s success derives from being a generalist with much "ecological flexibility" in regard to the conditions under which it engages and succeeds in reproduction. Turnock et al. (2003) monitored the relative abundance of the more common native coccinellids in alfalfa on the shore of Lake Manitoba, Canada over twelve years, by sweepnet and visual sampling following the introduction of Coccinella septempunctata. The trends of annual changes in the abundance of six species in southern Manitoba were similar, irrespective of sampling methods. Before 1988, Hippodamia tredecempunctata, Coccinella transversoguttata, and Hippodamia convergens were the most abundant species, followed by Hippodamia parenthesis and Coccinella trifasciata. By 1992, Coccinella septempunctata had become the dominant species, but Hippodamia tredecempunctata has since been the dominant species in most collections. The relative abundance of Coccinella transversoguttata, Hippodamia convergens, Hippodamia parenthesis, and Coccinella trifasciata has decreased since the establishment of Coccinella septempunctata. The decline in abundance of these species seems to be caused by their competitive displacement by Coccinella septempunctata. Their displacement also might be a contributing factor in the slight increase in abundance of Hippodamia tredecempunctata because Coccinella septempunctata may compete less directly with this species than with other native coccinellids. Schellhorn et al. (2005) provide an interesting example of where a biological control agent can present a risk to a non-target native species if they co-occur spatially and temporally, and if the agent will harm the native species. They sampled two study sites during 1993 in Minnesota and Wisconsin to survey predators and parasitoids of the extant populations of the United States federally endangered Karner blue butterfly (Lycaeides melissa samuelis, see picture below).
Karner blue butterfly, image by J & K Hollingsworth, U.S. Fish & Wildlife Service, public domain Schellhorn et al. found the introduced coccinellid Coccinella septempunctata co-occurring spatially and temporally with eggs, larvae and adults of the butterfly. The two species were also observed together on the latter(tm)s sole host plant, Lupinus perennis, and in Wisconsin, an adult Coccinella septempunctata was observed consuming second instar larvae of the butterfly. Using a simple model to hypothesize the risk, they showed that increases in predator density could greatly increase mortality to the butterfly. At these sites, the ladybird was reproducing and had access to summe? aphids and suitable overwintering habitat. Nearby agricultural crops could provide spring aphids for oogenesis, and assist with coccinellid population build-up. Maintaining a minimum isolation distance between agricultural crops known to harbour aphids and extant endangered butterfly populations may need to be considered as part of the butterfly management programme. Also in the USA, Lucas et al. (2002) looked at the effect of the newly arrived Asian coccinellid Harmonia axyridis on both the (native) Coelomegilla maculata and the previously invasive Coccinella septempunctata regarding the biological control and dispersion of apple mites and aphids. Assemblages of adults of the three coccinellid species were tested on apple saplings and on apple trees against Aphis citricola and Tetranychus urticae. The presence or substitution of adults of Harmonia axyridis for adults of Coelomegilla maculata or Coccinella septempunctata did not reduce the predation impact on mite or aphid prey. Harmonia axyridis was a more efficient predator of mites than was Coccinella septempunctata and generated lower prey dispersal from host plants. Substitutions of adults of Harmonia axyridis for those of Coelomegilla maculata, and in some cases of Coccinella septempunctata, resulted in greater reduction in number of aphids, suggesting that Harmonia axyridis may be a more efficient predator of aphids than either of the previously established coccinellids. Augmentative releasesAugmentative releases of Coccinella septempunctata in the field have not generally been very successful. If adults are released they tend to disperse, rather than feed and reproduce where they have been released. Perhaps because of this, seven-spot ladybirds do not seem to be available for purchase either as adults or larvae, despite the fact that some companies use pictures of seven-spot ladybirds to represent the ladybird they provide (for example Green Gardener in UK, which provides both larvae and adult two-spot ladybird, Adalia bipunctata). When coccinellids are released into 'protected' crops, for example in greenhouses, the use of Coccinella septempunctata for biological control has met with a higher level of success. Obrycki & Kring (1998) note that augmentative releases of several coccinellid species are well documented and effective, but ineffective species continue to be used because of ease of collection. Riddick (2017) reviewed the conditions needed for successful aphid control by ladybirds in greenhouses. Hamalainen (1977) used the ladybirds Coccinella septempunctata and Adalia bipunctata for control of aphids on sweet peppers, chrysanthemums and roses in small greenhouses. A single release of 1st instar larvae of both species reduced aphid populations on crop plants. When aphid density was compared between control, commercial greenhouses (no predators released), and experimental greenhouses, both ladybird species curbed population growth of Myzus persicae (see picture below) on chrysanthemum (Chrysanthemum morifolium) and sweet pepper (Capsicum annuum), respectively, in 8-10 days at several release rates. The release rate (number of ladybirds : number of aphids) did not appear to have an effect on aphid reduction.
Valerio et al. (1977a) tried different approaches to manage Aphis gossypii on strawberry plants. The practice of removing old leaves from plants (i.e., cultural control) was useful in managing low density populations. At high densities, Coccinella septempunctata (or Harmonia axyridis) were released on leaves, flowers, and fruit. The same researchers Valerio et al. (1977b) released Coccinella septempunctata to suppress Aphis gossypii and Aphis craccivora on sweet pepper. The authors suggested that both ladybird species contributed to aphid population reduction in the test greenhouse in contrast to the control greenhouse which had no ladybirds. Valerio et al. (1977b) also released the parasitoid Aphidius colemani to suppress the aphid Myzus persicae in the same greenhouse. They found that the parasitoid was capable of controlling low density populations of Myzus persicae, but did not indicate whether Coccinella septempunctata had a positive or negative effect on Aphidius colemani. Riddick (2017) suggests that an ideal scenario would be the co-existence of ladybirds and aphid parasitoids with limited or no intraguild predation. Laboratory and greenhouse cage experiments have shown that aphid parasitoids are able to detect aphid aggregations in which a ladybird is foraging, or has been foraging, and to avoid those aggregations. They may achieve this by being able to detect chemical signals left behind on foliage by ladybird beetles. Integrated control & conservation biological controlAtwal & Sethi (1963) investigated the population dynamics of the aphid Lipaphis erysimi and the predator Coccinella septempunctata on cabbage in an outdoor insectary and in the field in India. In the absence of Coccinella (and other enemies), population growth of Lipaphis was halted after a time. This was attributed partly to the hardening of mature leaves and partly to the deleterious effects of high Lipaphis density on the plant as a source of food. The experiments suggested that predation by Coccinella could limit Lipaphis populations at a lower level than intraspecific competition if the ladybird multiplied sufficiently fast. In fields, Coccinella did not begin to multiply until after the increase of Lipaphis had been limited, presumably by the deterioration of the food plant. This deterioration was attributed to changing weather conditions and by intraspecific competition. Francis et al. (2001) evaluated the contribution of aphidophagous ladybird populations to biological control in a vegetable crop. They noted that massive releases of entomophagous (=insect-eating) insects are expensive and time consuming, and a better approach may be to preserve of predator natural populations by reducing and by adapting chemical treatments in crop fields. Ladybird populations were assessed from May to June in broad bean fields (Vicia faba) in Belgium (thee picture below shows Aphis fabae on broad beans).
Three species made up more than 95% of the coccinellids - the aphidophagous Coccinella septempunctata and Propylea quattuordecimpunctata, and the fungus-eating Psyllobora vingintiduopunctata. The authors advocated integrated pest management as a reliable way to improve the quality of fresh vegetables and reduce pesticide residues. A prime component of integrated control is to use insecticides which cause minimum harm to natural enemy populations. Wiles & Jepson (1994) looked at the sub-lethal effects of deltamethrin residues on the within-crop behaviour and distribution of Coccinella septempunctata. The behaviour and distribution of adult coccinellids were recorded in two plots of winter wheat infested with the cereal aphids Sitobion avenae and Metopolophium dirhodum. One plot was sprayed with the pyrethroid insecticide deltamethrin and the other was left unsprayed. Single ladybird beetles were released sequentially on the ground at the centre of the sprayed and unsprayed plots and their behaviour and position in the crop canopy were recorded at 30 second intervals for a total of 15 min per beetle. Significant differences were found between the overall behaviour patterns of Coccinella septempunctata in the untreated and deltamethrin treated plots up to three days after the spray application. Ladybird beetles exposed to deltamethrin residues were observed to walk and groom significantly more frequently and to rest significantly less frequently than those in the unsprayed plot. The results were discussed in terms of possible evidence for the repellency of deltamethrin to Coccinella septempunctata and also the implications for integrated pest management of changes in predator behaviour and crop distribution resulting from sub-lethal uptake of insecticides. Bozsik (2006) looked at the susceptibility of adult Coccinella septempunctata to five 'insecticides' (pyriproxifen, imidacloprid, deltamethrin + heptenophos, lambda-cyhalothrin and Bacillus thuringiensis). Pyriproxifen, imidacloprid and Bacillus thuringiensis seemed to be safe for adult ladybirds, but the other two preparations were moderately harmful to them. Roy et al. (2001) assessed the potential of adult and larval Coccinella septempunctata as vectors of the aphid-specific entomopathogenic fungus Pandora neoaphidis through a series of laboratory and field experiments. The ability of coccinellids to transmit conidia from a colony of Pandora neoaphidis-infected pea aphids (Acyrthosiphon pisum), to a colony of uninfected pea aphids was demonstrated in a laboratory study. A field study further demonstrated the potential of coccinellids to transmit Pandora neoaphidis. No aphids died of the fungus in the control treatments, but 5, 16 and 33% of aphids were infected with it in the other treatments. Modelling studiesIn China the cotton aphid (Aphis gossypii) is the key insect pest of seedling cotton, particularly in the North China cotton region, with annual losses amounting to 10-15% of the attainable yield. Sole reliance on insecticides against the cotton aphid in the past four decades has brought about a rapid development of insecticide resistance, serious outbreaks of key pests, resurgence of secondary pests, and risks for man and the environment. Biological control of the cotton aphid by the naturally-occurring Coccinella septempunctata was the first priority for integrated pest management in cotton to avoid early season application of insecticides and lay a?foundation for biological control of aphids and other pests during the season. The most commonly used approach for cotton aphid biological control is to augment the coccinellid population by intercropping cotton with wheat. But the downside of this approach is decreased fibre and seed quality, increased outbreaks of cotton bollworm and verticillium wilt and difficulties with mechanization. There is, therefore, a demand for developing more viable cotton-wheat intercropping systems. Xia (1997) sought to better understand and quantify the major processes in C. septempunctata - A. gossypii system in cotton monoculture and cotton-wheat intercrop by developing simulation models of the dynamics of the coccinellid - aphid system in both cotton cropping systems. It was planned to use the models to explore intercropping strategies that are not only favourable for biological control but also advantageous with respect to fibre and seed quality, as well as suppression of the cotton bollworm and verticillium wilt by cultural practices. Bianchi & Van der Werf (2003) used simulation modelling to study the effect of the shape, area, and fragmentation of non-crop landscape elements on the control of aphids by Coccinella septempunctata. The model was based on a description of the phenology and population dynamics of aphids and the coccinellid, as well as the predation dynamics and predator dispersal characteristics. The study compared biocontrol in 12 landscapes consisting of field crops and hedgerows that differ in the shape, proportion, and fragmentation of the hedgerow elements in the landscape. Linear hedgerow elements provided better control than square elements in 3 of the 12 simulated landscapes and resulted in similar levels of control in the other nine landscapes. The total area of hedgerow habitat was the key factor for the control of aphid populations. Landscapes with 9% and 16% non-crop habitat had large enough local populations of Coccinella septempunctata to control aphid infestations, whereas landscapes with only 1% or 4% of hibernation area had no potential for improved aphid control. The ladybird Coccinella septempunctata depends on non-crop landscape elements, such as hedgerows, for hibernation (see picture below of ladybirds hibernating in gorse bush).
Biology & EcologyFeeding behaviourGurney & Hussey (1970) evaluated four species of Coccinellidae, Adalia bipunctata, Coccinella septempunctata, Coelomegilla maculata and Cycloneda sanguinea for biological control of aphids on cucumbers and chrysanthemums. In laboratory feeding tests Coelomegilla maculata and Cycloneda sanguinea proved the most voracious, but the former could not remain on cucumber foliage long enough to be effective. The fecundity of Cycloneda sanguinea (see picture below) was the highest of those studied and a satisfactory laboratory rearing technique has been developed for this species.
Spotless lady beetle in Florida, image copyright Judy Gallagher under a Creative Commons Attribution 2.0 Generic license Obrycki & Orr (1990) looked at the suitability of three prey species for the coccinellids Coccinella septempunctata, Hippodamia variegata, and Propylea quattuordecimpunctata. Acyrthosiphon pisum was found to be a highly suitable larval prey for Nearctic populations of these predators, so redistribution program releases in alfalfa infested with Acyrthosiphon pisum are appropriate. In corn, these coccinellids can develop on Rhopalosiphum maidis, but first instars cannot utilize eggs of the European corn borer moth (Ostrinia nubilalis as an alternate food source. Nedved & Salvucci (2008) investigated the preference of larvae and adults of Coccinella septempunctata for three aphid species: two edible species Acyrthosiphon pisum and Aphis philadelphi, and a toxic prey Aphis sambuci (see picture below).
Surprisingly, the toxic aphid was consumed at twice the rate of the two essential prey species. Under field conditions on elder (Sambucus nigra) Aphis sambuci is usually avoided by Coccinella septempunctata. Laboratory experiments demonstrated that ladybirds fed on aphids without choice in the beginning of experiment when they were hungry. The ladybirds did express preference thereafter, but they did not choose the most profitable species. Shannag & Obeidat (2008) found that partial resistance combined with predation was more effective in lessening aphid numbers on faba bean than either the predator or the plant resistance alone. Laboratory tests showed that prey, Aphis fabae, raised on susceptible cultivar was more suitable for the predator as food source, enhancing the development rate and fecundity, than aphids fed on the partially resistant cultivar. Feeding the predator on aphids from the partially resistant cultivar prolonged the embryonic larval developmental time and the time required from egg laying to adult emergence by several hours. Adult longevity was not influenced by the aphid source. Khan & Yoldas (2018) investigated the occurrence of cannabilistic behaviour in Coccinella septempunctata. They found the adults and older larvae cannibalized the eggs and young larvae of their own species. We have also noted cases of cannibalism of larger larvae by the adults (see picture below).
Host-finding behaviourIn Iowa, early in the growing season of soybean (Glycine max), Zhu & Park (2005) observed many predacious seven-spot ladybirds on plants with heavy infestations of soybean aphid, Aphis glycines. They studied whether the attraction of this beetle is caused by the release of specific volatile compounds of soybean plants inf?sted by aphids. Gas chromatography-mass spectrometry analyses revealed consistent differences in the profiles of volatile compounds between aphid-infested soybean plants and undamaged ones. Significantly more methyl salicylate was released from infested plants at both the V1 and V2 plant growth stages and methyl salicylate elicited significant electrophysiological responses in Coccinella septempunctata. In field tests, traps baited with methyl salicylate were highly attractive to adult Coccinella septempunctata, whereas 2-phenylethanol was most attractive to the lacewing Chrysoperla carnea and syrphid flies. It was concluded that Coccinella septempunctata probably uses methyl salicylate as the olfactory cue for prey location. Ninkovic & Pettersson (2003) investigated the odour mechanisms affecting habitat preferences of Coccinella septempunctata. In a field study, the frequency of adult Coccinella septempunctata was higher in barley plots containing high densities of the common weeds, creeping thistle (Cirsium arvense) and couch grass (Elytrigia repens), than in control plots with only barley. In olfactometer experiments in the laboratory, adult Coccinella septempunctata) showed a significantly more positive response to mixed odours of barley and each of the two weeds than to barley alone. Ladybirds responded differently to barley plants that were previously exposed to volatiles from the two weeds. The couch grass-exposed barley plant lost its attractivity while the creeping thistle-exposed barley plants maintained attractivity. As no aphids or pollen resources were present in the plots during the experiment, the results show that Coccinella septempunctata responds to the botanical characteristics of the habitat even if no food resources are available. These results strongly suggest that olfactory cues and plant-plant communication from diversified plant stands can be important mechanisms in predator attraction to sites with a complex botanical diversity. Aphids produce large amounts of sugar-rich honeydew which is used by many other insects, such as the Bombus hypnorum shown in the picture below feeding on honeydew from the rosy apple aphid (Dysaphis plantaginea).
Ide et al. (2007) looked at the use of honeydew as a cue to find aphids by larvae of Coccinella septempunctata. More larvae responded by climbing the plants with aphids than responded to plants without aphids. When the plants were replaced with sticks, in order to exclude visual and olfactory cues from plants and aphids, more larvae of Coccinella septempunctata climbed sticks above the area that contained honeydew than climbed sticks above the area that did not contain honeydew. It was concluded that ladybird larvae use honeydew as a contact kairomone when foraging for aphids. Aphis craccivora deposited a larger number of honeydew droplets beneath the plants than did similar numbers of Acyrthosiphon pisum. As a result, Coccinella septempunctata larvae licked more frequently the honeydew of Aphis craccivora than that of Acyrthosiphon pisum and spent longer searching on the area containing honeydew of Aphis craccivora than that of Acyrthosiphon pisum. Consequently, a larger number of larvae climbed a stick above honeydew of Aphis craccivora than that of Chang (1996) used an experimental approach to compare the value of using multiple as opposed to a single species of natural enemies for biological control. The behavior and effectiveness of predator species used either singly or in combination to control bean aphids, Aphis fabae. The predators were larvae of a lacewing, Chrysoperla plorabunda, and the coccinellid, Coccinella septempunctata. Treatments comprised similar numbers of larvae of each species versus the same total number larvae of one or the other species. The predators slowed the growth of aphid populations. No evidence of interaction between the predator species could be seen in terms of their effects on the sizes of the final aphid populations. This was explained by the finding that larvae of the lacewing and the coccinellid differed significantly in where they were most frequently found on the plant. Also no clear evidence for intraguild predation was found.
Sato et al. (2005) looked at the dropping behaviour of larvae of aphidophagous ladybirds and its effects on incidence of intraguild predation between the intraguild prey, Adalia bipunctata and Coccinella septempunctata, and the intraguild predator Harmonia axyridis. Two experiments were performed in the laboratory to assess the behaviour of dropping from a host plant as a defence against intraguild predation. In the first experiment, encounters were observed on bean plants between fourth instars of Harmonia axyridis, and first instars of the two ladybird prey species. The percentages of first instars of the two prey species that dropped from the plant in response to attack differed dramatically, with 47.5% of Coccinella septempunctata first instars dropping versus 0% of Adalia bipunctata.
In the second experiment, first instars of the two ladybird prey species and a fourth instar of Harmonia axyridis were allowed to forage together on bean plants for 3 h. During this time, 44.3% of Coccinella septempunctata larvae dropped from the plant, but less than 2% of Adalia bipunctata larvae did so. In contrast, 95.0% of i>Adalia bipunctata larvae fell victim to intraguild predation by Harmonia axyridis versus only 54.5% of Coccinella septempunctata larvae. It was concluded that Adalia bipunctata were more vulnerable to intraguild predation than Coccinella septempunctata.
Nakashimaet al. (2004) investigated the role of semiochemicals in mediating intraguild interactions between the seven-spot ladybird Coccinella septempunctata, and the aphid parasitoid, Aphidius ervi. Female parasitoids avoided leaves visited by ladybird adults and larvae during the previous 24 hr. Ethanol extracts of coccinellid adults and larvae also induced avoidance responses by the parasitoid. Two of the hydrocarbons identified, when tested individually at levels found in the adult extract, induced avoidance by the parasitoid. Further investigation of the larvae extract, and footprint chemicals deposited by adults in glass Petri dishes, confirmed the presence of the hydrocarbons. Parasitism rates of the pea aphid, Acyrthosiphon pisum, on broad bean plants, Vicia faba, which had been sprayed with a mixture of the chemicals, were lower than those on control plants. The effect, however, was no longer evident if parasitoid foraging was delayed by 24 hr after the plants were treated.
Nakashima et al. (2006) showed that females of three parasitoid species, Aphidius eadyi, Aphidius ervi, and Praon volucre, detected chemical trails on leaves vi?ited by Coccinella septempunctata and Adalia bipunctata.
Image of Aphidius ervi copyright Nikk from Peterborough, UK under a Creative Commons Attribution 2.0 Generic license.
Xue et al. (2012) showed that the presence of aphid parasitoids on shared plants could affect the ability of ladybirds to reduce aphid densities. Aphid parasitoids and ladybirds typically interact when ladybirds come in contact with parasitized aphids. In the laboratory, ladybirds (Harmonia axyridis and Coccinella septempunctata, larvae and adults) consumed un-parasitized aphids as readily as newly parasitized ones, but did not prefer consuming mummified aphids.
We especially thank Brian & Val for inviting us into their apple orchard at Picket Piece to hunt for & discuss aphids, also Plumpton College at Stanmer Park, Hadlow College and Middle Farm, East Sussex for their kind assistance, and permission to sample.
For coccinellid identification we have used Hackston and ICAR Featured Insects Factsheets for the key characteristics, together with the latest Wikipediaaccount for each species.
For aphids we have made provisional identifications from photos of living specimens, along with host plant identity using the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).
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_Katja Schulzew.jpg "Rodolia cardinalis (vedalia beetle) at Els Poblets, Alicante, Spain on 4/11/14; Katja Schulz.")
