Native Ladybird Research Articles

Interactions between the parasitoid wasp Dinocampus coccinellae and two species of coccinellid from Japan and Britain

The establishment, spread and increase of the invasive coccinellid Harmonia axyridis Pallas in North America and Britain have coincided with declines in native ladybirds. In Britain, this pattern was predicted soon after H. axyridis was first recorded. However, predictions of the impact that H. axyridis may have on the parasites, parasitoids and pathogens of native coccinellids have been less certain, largely because of uncertainty over whether H. axyridis would become an alternate host for such agents. Dinocampus coccinellae (Schrank) is a braconid parasitoid of ladybirds of the sub-family Coccinellinae. In Japan, this wasp uses both Coccinella septempunctata brucki Mulsant and H. axyridis as hosts, but successfully parasitizes a higher proportion of the former species. Data are here presented that indicate the same is true in Britain, but to a greater extent. This study investigates the interactions of D. coccinellae with C. septempunctata L. and H. axyridis from Japan and Britain. We show that coccinellid activity affects encounter rates with the wasp, with H. axyridis being more active than C. septempunctata in the tests. Escalation rates from investigation to ovipositional attack were higher for C. septempunctata than H. axyridis for both Japanese and British wasps. Wasp emergence was higher, relative to ovipositional attack, from C. septempunctata than from H. axyridis. Wasps did not discriminate between Japanese and British ladybirds of the same species. British wasp eclosion rates were higher from Japanese than from British H. axyridis. We consider both the effect D. coccinellae may have on H. axyridis population demography, and the effect H. axyridis may have on D. coccinellae in Europe.

Estimation of mortality by entomophages on exotic Harmonia axyridis versus native Adalia bipunctata in semi-field conditions in northern Italy

A semi-field experiment was carried out in two peach orchards in northern Italy to assess mortality due to predators and parasitoids on the exotic coccinellid Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in comparison with the native coccinellid Adalia bipunctata L. (Coleoptera: Coccinellidae). The experiments were conducted in cages to avoid the possible escape of the exotic ladybird (not yet established in Italy). Two kinds of cage experiments were included: ‘exclusion cages’ (access by walking predators impeded) and ‘free cages’ (walking predators free to enter). The cages, containing all the stages of the two ladybird species, were placed in two localities and left for 24 h. All ladybird stages used for the semi-field experiments came from a laboratory rearing. The eggs of H. axyridis experienced less mortality than those of A. bipunctata. The ant workers were the most frequent predators in ‘free cages’ but A. bipunctata cannibalism on eggs was also detected. Larvae of both coccinellid species were predated equally but larval predation of L1 and L2 was higher in comparison to predation of L3 and L4. Pupae and adults of both exotic and native ladybirds were never attacked by predators. Predation on younger larval stages was higher in the ‘free cages’ in comparison with ‘exclusion cages’. No ladybird parasitisation was observed. The ‘free cage’ technique seems to provide a standardised and realistic estimation of predation impact but more studies are needed to evaluate ladybird parasitisation in semi-field conditions.

Predation by Adult and Larval Lady Beetles (Coleoptera: Coccinellidae) on Initial Contact with Lady Beetle Eggs

Naïve adults and larvae of the native lady beetles Coleomegilla maculata (DeGeer), Cycloneda munda (Say), Hippodamia convergens Guérin-Méneville, Olla v-nigrum (Mulsant), and the exotic lady beetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) were tested for their initial response to eggs of these five lady beetle species and for egg consumption on first contact and after 3 h. Additionally, field-collected O. v-nigrum and H. axyridis adults were tested. C. maculata, H. axyridis, and O. v-nigrum adults responded similarly to all egg species on first contact. Higher numbers of C. munda adults did not eat C. maculata, H. convergens, and O. v-nigrum eggs on first contact compared with numbers that did eat C. munda and H. axyridis eggs. H. convergens adults always ate C. munda eggs but hardly ate H. axyridis eggs on first contact. Results showed that over the 3-h interval, egg predation by those predators feeding on first contact was always higher, except for adults and larvae of C. maculata, than for those that did not feed on first contact. Thus, acceptance of eggs on initial contact does impact egg survival. It is likely that eggs of all native species tested (i.e., C. maculata, C. munda, H. convergens, and O. v-nigrum), but not exotic H. axyridis eggs, are suitable food for C. maculata, H. convergens, and O. v-nigrum, whereas only C. munda eggs serve as suitable food for C. munda. In direct contrast, all egg species tested would likely serve as suitable food for the exotic H. axyridis.

Aggregation of polyphagous predators in response to multiple prey: ladybirds (Coleoptera: Coccinellidae) foraging in alfalfa

AbstractThe spatial distribution of polyphagous predators may often reflect the integration of aggregative responses to local densities of multiple species of prey, and as such may have consequences for the indirect linkages among the prey sharing these predators. In a factorial field experiment in which we manipulated local prey densities within a field of alfalfa in Utah (USA), we tested whether aphidophagous ladybirds would aggregate not only in response to their primary aphid prey, but also in response to an abundant alternative prey, the alfalfa weevil (Hypera postica [Gyllenhal]). Native North American ladybirds (primarily Hippodamia convergens Guerin and H. quinquesignata quinquesignata [Kirby]) responded only to spatial variation in aphid density. In contrast, the introduced ladybird, Coccinella septempunctata L., aggregated also at local concentrations of the weevil late in the experiment when weevil density was high and aphid density was relatively low throughout all experimental plots. The results support the hypothesis that C. septempunctata is more responsive than are native ladybirds to the availability of alternative prey in alfalfa, which may account in part for the displacement of native ladybirds from alfalfa by the introduced species as aphid numbers have declined. The differing responses of the native and introduced ladybirds to spatial patterns of the alternative prey underscore the importance of extending the study of predator aggregation to understand better how polyphagous predators distribute themselves in response to spatial patterns of multiple species of potential prey.

Interference competition between ladybird beetle adults (Coleoptera: Coccinellidae): effects on growth and reproductive capacity

AbstractCage experiments were used to determine the minimum number of Aphis fabae Scopoli that females of the Azorean native ladybird beetle Coccinella undecimpunctata L. require per day to achieve maximum fecundity and to assess the effects of interference competition from conspecific and heterospecific [Harmonia axyridis (Pallas)] adult ladybirds on its growth and reproduction. The number of A. fabae at which females of C. undecimpunctata ate most aphids, achieved maximum reproduction and maintained their body weight, was 200. The presence of H. axyridis adults, unlike the presence of C. undecimpunctata, significantly affected the reproductive numerical response of C. undecimpunctata even though the resource was not in short supply. The results suggest that interference competition with heterospecifics may adversely affect the reproductive capacity of C. undecimpunctata. Based on previous results and those reported here, we suggest that the introduction of H. axyridis could endanger the population abundance and/or result in the competitive displacement of C. undecimpunctata from the Azorean ecosystem.

Interactions between introduced and native predatory ladybirds (Coleoptera, Coccinellidae): factors influencing the success of species introductions

Abstract. 1. Why some exotic species invade successfully while others do not is poorly understood. This study focuses on the inability of the exotic predatory ladybird Adalia bipunctata (L.) (Coleoptera, Coccinellidae) to establish and spread in Japan. In particular, this study considers the interactions between A. bipunctata and three native Japanese ladybird species, Harmonia axyridis Pallas, Coccinella septempunctata Linn., and Propylea japonica Mulsant.2. The number of aphids occurring on the host plants declined dramatically over the course of larval development in the presence of H. axyridis or C. septempunctata. In contrast, many aphids remained at the end of the experiment when only A. bipunctata or P. japonica was present.3. The survivorship of A. bipunctata from second instar to adult was significantly reduced in the presence of H. axyridis, but not in the presence of C. septempunctata or P. japonica. Most deaths were the result of intra‐guild predation when H. axyridis or C. septempunctata larvae were present. Larvae of H. axyridis and C. septempunctata suffered very high mortality in this experiment, but survived better when co‐occurring with A. bipunctata than when occurring only with conspecifics. In contrast, P. japonica survived better when occurring with conspecifics than with A. bipunctata.4. The finding that larvae of the exotic species A. bipunctata died at high rates from intra‐guild predation by the native Japanese ladybirds H. axyridis and C. septempunctata may bear on the question of why A. bipunctata has not established more successfully in Japan whereas H. axyridis and C. septempunctata have been very successful in establishing themselves in North America.

Effects of native ladybirds on oviposition of the exotic species, Adalia bipunctata (Coleoptera: Coccinellidae), in Japan

Effects of native ladybird females of Harmonia axyridis Pallas and Coccinella septempunctata L. on oviposition behavior of the exotic species, Adalia bipunctata (L.), were assessed by pairing females of the exotic species with conspecific or heterospecific females. Pairs of females were provided with aphids in excess for 30 days, during which time there were no significant differences in weight, rates of mortality, or selections of sites for oviposition among the treatments. However, females of A. bipunctata laid significantly fewer eggs over the 30-day experimental period when paired with females of H. axyridis or C. septempunctata than when paired with conspecifics, even though aphids were abundantly available in all three cases. The number of eggs laid by a female of A. bipunctata paired with conspecifics gradually declined over the 30-day experimental period, while egg production declined especially rapidly during the second ten-day period when females were paired with females of H. axyridis and C. septempunctata. Thus, egg production by females of the exotic species was reduced in the presence of the native ladybirds.

Expansion of the geographical distribution of an exotic ladybird beetle,Adalia bipunctata(Coleoptera: Coccinellidae), and its interspecific relationships with native ladybird beetles in Japan

AbstractThe first record of the exotic ladybird beetle,Adalia bipunctata(Coleoptera; Coccinellidae), in Japan was in 1993 at Osaka Nanko Central Park. Since that time, studies on the life history and geographical distribution ofA. bipunctatahave been ongoing, and its establishment in the Osaka Nanko area has been confirmed.A. bipunctatais a predacious ladybird beetle and a member of a guild that overlaps in habitat and prey with that of native ladybird beetles such asHarmonia axyridisandMenochilas sexmaculatus. We investigated the distribution ofA. bipunctataand its interspecific relationships with native predacious ladybird beetles. In some areas,A. bipunctatawas dominant in interspecific relationships with native ladybird beetles. For the first 10 years afterA. bipunctatawas discovered, it occurred only in the Osaka Nanko area, but the present geographical distribution indicates that it has expanded its range. Though the population density of this species was highest at the area recorded first, and tended to decrease in inverse proportion to the distance from Osaka Nanko Central Park, a satellite occurrence was observed in a remote area. The numbers of aphid and tree species (leaf shelter for aestivation and over‐wintering) utilized byA. bipunctatahave recently increased. Such increases will cause the rate of distribution ofA. bipunctatato accelerate. Interspecific competition betweenH. axyridisandA. bipunctata, which occurs earlier thanH. axyridis, may be avoided by desynchronization of the occurrence seasons, and another common predacious ladybird beetle,Coccinella septempunctata, may escape interspecific competition by habitat segregation.

Susceptibility of lady beetles (Coleoptera: Coccinellidae) to entomopathogenic nematodes

We investigated differential susceptibility of lady beetles to entomopathogenic nematodes, for two reasons: (1) to estimate potential nontarget effects on natural lady beetle populations, (2) to compare the susceptibility of exotic versus native lady beetle species. We hypothesize that successful establishment of some exotically introduced arthropods may be due, in part, to a lower susceptibility relative to competing native species. In laboratory studies, we compared the pathogenicity, virulence, and reproductive capacity of Heterorhabditis bacteriophora and Steinernema carpocapsae among two native ( Coleomegilla maculata and Olla v-nigrum) and two successfully established exotic ( Harmonia axyridis and Coccinella septempunctata) lady beetles, and a known susceptible lepidopteran host, Agrotis ipsilon. After 1 and 2 days of exposure to either nematode species, mortality of A. ipsilon was higher than in all lady beetles. Thus, we predict that nematode field applications would have significantly less impact on lady beetle populations than on a susceptible target pest. Additionally, the impact of soil-applied nematodes may be lower on lady beetles than on soil-dwelling hosts because the former spends relatively less time on the soil. Exotic lady beetles were less susceptible to nematode infection than native species. Reproductive capacity data also indicated lower host suitability in H. axyridis, but not in C. septempunctata. Overall, the hypothesis that low susceptibility to pathogens in certain exotic lady beetles may have contributed to competitive establishment was supported (especially for H. axyridis). Additional studies incorporating different hosts and pathogens from various geographic locations will be required to further address the hypothesis.

Suitability of exotic and native lady beetle eggs (Coleoptera: Coccinellidae) for development of lady beetle larvae

Abstract Predation upon lady beetle (Coleoptera: Coccinellidae) eggs in the field is most often instances of egg cannibalism by larvae or adults while the majority of the remaining predation events upon coccinellid eggs is done by other species of Coccinellidae. Thus the recent introduction and establishment of Harmonia axyridis in the US could negatively affect native species of Coccinellidae via egg predation. However, little is known regarding the suitability of interspecific coccinellid eggs as a food source for larval development. In this study, it was found that native first or third instar Coleomegilla maculata and Olla v-nigrum larvae were incapable of surviving to the adult stage when provided solely exotic H. axyridis eggs. In stark contrast, H. axyridis larvae survived equally well when cannibalizing eggs or eating eggs of either native species. When C. maculata and O. v-nigrum were grouped as ‘native’ and compared with the exotic H. axyridis, more native eggs were attacked than exotic eggs and a higher percentage of eggs was attacked by H. axyridis larvae. Native and exotic larvae attacked a similar percentage of native eggs but native larvae attacked significantly fewer exotic eggs than did exotic larvae. These data suggest that H. axyridis may prey upon the eggs of these native species, when encountered in the field, compared with the likelihood of the native species preying upon H. axyridis eggs. Therefore, eggs of the native species C. maculata and O. v-nigrum will continue to be subjected to cannibalism and also to possible predation by other native species and the exotic H. axyridis.

Competitive interactions between an exotic and a native ladybeetle: a field cage study

AbstractWe conducted field‐cage studies on the direct interactions between a coccinellid species native to North America, Coleomegilla maculata De Geer, and a species introduced from Asia, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). We compared the mortality and weight gain of larvae of both species in field cages that enclosed one or both species with corn plants containing high or low aphid numbers. We did not find a significant effect of the presence of H. axyridis on the survival or weight gain of C. maculata, but H. axyridis larvae weighed more when kept with C. maculata for 5 days than when kept with equal numbers of conspecifics. This suggests that intraspecific competition was stronger for H. axyridis than the interspecific competition with C. maculata. The spatial distribution of C. maculata over the plants differed between single‐species and two‐species treatments in a manner that suggested that this species avoided interactions with H. axyridis.

HABITAT DISPLACEMENT OF NORTH AMERICAN LADYBIRDS BY AN INTRODUCED SPECIES

How introduced species displace native species is often poorly understood. Various studies suggest that several species of native ladybird beetles (Coleoptera: Coccinellidae) have declined in abundance in particular habitats (especially crops) and/or geographic regions following the colonization of North America by the seven-spotted ladybird beetle (Coccinella septempunctata L.). However, the factors responsible for such declines are unclear. Long-term sampling of alfalfa fields in northern Utah revealed that as C. septempunctata established itself and increased in numbers, densities of native species decreased significantly over the period 1992–2001. The decline in numbers of native ladybirds mirrored a decline in numbers of their principal prey in alfalfa, pea aphids. Field experiments with induced aphid outbreaks were conducted to test the hypothesis that dispersing native adults have shifted their foraging efforts away from alfalfa as the introduced species has increased in numbers and depressed prey availability. As predicted by the hypothesis, native ladybirds rapidly reaccumulated in alfalfa when prey became abundant. Their presence was brief, however, as they and especially the more numerous C. septempunctata quickly suppressed experimental aphid outbreaks. The ratio of densities within experimental plots with high aphid numbers to densities in the surrounding field was greater for native ladybirds than for C. septempunctata. Also, densities of native ladybirds varied more closely with aphid densities among fields in late May 2001 than did densities of C. septempunctata. Hence, native ladybirds appear especially responsive to local aphid density. C. septempunctata's impact on aphid density in alfalfa appears to have reduced significantly the degree to which the habitat retains foraging native adults. Thus, introduced species may influence the distribution and abundance of native competitors not only by reducing survivorship in local habitats, but also by altering the dynamics of dispersal and habitat use across the landscape.

Changes in A Lady Beetle Community Following the Establishment of Three Alien Species

A number of recent studies indicated that establishment of exotic lady beetles (Coleoptera: Coccinellidae) may have adverse affects on native lady beetle species. In the present study, we analyzed changes in coccinellid community inhabiting potato crops in northern Maine over the past 31 years. Prior to 1980, lady beetle communities were comprised almost exclusively of the two native species, Coccinella transversoguttata Brown and Hippodamia tredecimpunctata(Say). Starting 1980, an exotic species Coccinella septempunctata L. became permanently established in potato crops and quickly started to dominate lady beetle community. Two other exotic species, Harmonia axyridis(Pallas) and Propylea quatordecimpunctata(L.) became prominent members of the lady beetle community in 1995 and 1996. Invasion by exotic species was followed by a significant decline in the abundance of C. transversoguttata and H. tredecimpunctata, and a significant increase in the overall diversity of lady beetle community. The abundance of aphid prey was substantially reduced after the establishment of H. axyridis. The observed trends demonstrate the profound effects that exotic natural enemies may have on target and non-target native species, and highlight the importance of their thorough evaluation before initiating biological control programs.

Susceptibility of a native and an exotic lady beetle (Coleoptera: Coccinellidae) to Beauveria bassiana

The exotic multicolored Asian lady beetle, Harmonia axyridis, became established and recently spread across much of North America and southern Canada. In a habitat now used by both the invading H. axyridis and a native lady beetle, Olla v-nigrum, we discovered that the native lady beetle was commonly infected by Beauveria bassiana; whereas, the exotic H. axyridis, was not. Laboratory assays revealed that B. bassiana isolates collected from naturally infected O. v-nigrum were pathogenic to adult O. v-nigrum but not to adult H. axyridis. In contrast, the GHA strain of B. bassiana was not significantly pathogenic to O. v-nigrum nor H. axyridis. Late-season field collections revealed significantly higher B. bassiana infection of O. v-nigrum than H. axyridis. Our results lead us to hypothesize that low susceptibility of H. axyridis to B. bassiana (found to infect O. v-nigrum) may provide an intraguild advantage to H. axyridis over O. v-nigrum; this may also occur with other species of native lady beetles and other endemic entomopathogens in different habitats and regions.

Indirect interactions between an introduced and a native ladybird beetle species mediated by a shared parasitoid

Abstract We studied parasitism rates by Dinocampus coccinellae (Schrank) of the native species Coleomegilla maculata De Geer and the introduced Harmonia axyridis (Pallas) in the laboratory and in the field. The rate of successful parasitism for H. axyridis was lower than for C. maculata , but the proportion of the population that had immature stages of the parasitoid was similar for both species. We used a population dynamics model to predict interactions between C. maculata , H. axyridis , and D. coccinellae , incorporating the differences in suitability we found between the two hosts. In the model, parasitoid attacks on non-suitable hosts contribute to parasitoid egg depletion without causing host death or parasitoid recruitment. Thus, hosts with low suitability could act as sinks for parasitoid eggs. Simulations of this model suggest that there is a critical value of the growth rate ( r ) for C. maculata below which C. maculata goes extinct. The critical r value is an increasing function of the attack rate on C. maculata (as expected) and a decreasing function of the attack rate on H. axyridis because the strength of H. axyridis as an egg sink increases with the attack rate on this species. Simulations of the model using experimentally derived parameter values suggest that the presence of H. axyridis leads to an increase in equilibrium densities of C. maculata . This outcome is due to the wastage of parasitoid eggs in the relatively unsuitable H. axyridis hosts.

Morphology of invasion: body size patterns associated with establishment of Coccinella septempunctata in western North America

The Old World ladybird Coccinella septempunctata has rapidly established itself as an abundant, widespread species throughout North America. Overwintering individuals of this species, and of native ladybirds, were collected from early season alfalfa in northern Utah during the period of initial establishment of the invader (1989 to 1999), and were measured for body size. Adult body size can vary widely within insect species, often reflecting differential success of individuals as immatures in obtaining food. Here I examine patterns of ladybird body size to address two questions associated with the establishment of C. septempunctata: (1) is there evidence for adverse impact on native species?, and (2) why has the invader has been so successful in establishment? As an indirect test of adverse competitive effect of the invader on native species, I determined whether mean body size of adults of the five most common native species (Coccinella tranversoguttata, Hippodamia convergens, H. quinquesignata, H. sinuata, and H. tredecimpunctata) declined over the period 1991-1997 as the invader increased rapidly in abundance. No such decline was observed for any of these species, thus providing no evidence that the invader's establishment has significantly increased scramble competition for food among immature ladybirds. I 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 (i.e., in having relatively high proportions of both unusually large and small individuals). Such results are consistent with the hypothesis that the invader's success derives from being a generalist with much ecological flexibility in regard to the conditions under which it engages and succeeds in reproduction.

Efficiency of Ladybeetles (Coccinellidae: Coleoptera) in Insect Control

A most remarkably effective control and often total elimination of some scale insects and exposed mealybugs by ladybeetles—Coccinellidae: Coleoptera—occurred on the tropical Island of Puerto Rico, affecting such introduced plants as coconut palm, grapefruit, bamboo, and Australian pine. No comparable control resulted of aphids, either by introduced ladybeetles or endemic species, presumably in ecologically balanced adjustment to their environment. Indeed, the native ladybeetles became scarce, or tended to disappear. None feeds on Myzus persicae, a major pest of eggplant and pepper, and most recently on tobacco. No instance of effective control of the yellow aphid of sugarcane, Sipha flava, due to ladybeetles, has been observed.

AN EXPERIMENT IN THE IMPORTATION OF BENEFICIAL INSECTS

In the February number of the Canadian Entomologist I gave the results of an experiment in the exportation of a few of our native lady beetles to South Africa. I now have the pleasure of giving the resurt of an experiment in the importation of some South African lady beetles.March 27th, Mr. C. W. Mally, Assistant Government Entomologist, sent me several specimens of Exochomus nigrmaculatus, and, quite a large number of two smaller, unnamed species. All of these attack more especially the Mealy bug, Dactylopius, in their native home. The consignment was made by simply fastening twigs of Oleander very badly affected with Mealy bug, to the bottom of the box, and putting the lady beetles among them. The package reached me April 23rd, and, strangely enough, there were but very few of the specimens that were not alive and active. The importation was thus an entire success.