Rebecca R. Smyth

Lessons from lady beetles: accuracy of monitoring data from US and UK citizen‐science programs

Citizen scientists have the potential to play a crucial role in the study of rapidly changing lady beetle (Coccinellidae) populations. We used data derived from three coccinellid-focused citizen-science programs to examine the costs and benefits of data collection from direct citizen-science (data used without verification) and verified citizen-science (observations verified by trained experts) programs. Data collated through direct citizen science overestimated species richness and diversity values in comparison to verified data, thereby influencing interpretation. The use of citizen scientists to collect data also influenced research costs; our analysis shows that verified citizen science was more cost effective than traditional science (in terms of data gathered per dollar). The ability to collect a greater number of samples through direct citizen science may compensate for reduced accuracy, depending on the type of data collected and the type(s) and extent of errors committed by volunteers.

A Male-Produced Aggregation Pheromone Facilitating Acalymma vittatum [F.] (Coleoptera: Chrysomelidae) Early-Season Host Plant Colonization

We conducted field studies to investigate the involvement of volatile cues in early-season host plant colonization by striped cucumber beetle, Acalymma vittatum (F.) (Coleoptera: Chrysomelidae). Wind-directed traps were baited with male or female A. vittatum, potted cucumber (Cucumis sativus) seedlings that were of near-isogenic lines which either contained or lacked cucurbitacin, or combinations of male or female A. vittatum feeding on one or the other cucumber variety. We found no response to undamaged plants of either cucumber variety or plants that were actively being fed upon by A. vittatum females, whereas the response to volatiles associated with male A. vittatum was strong. Both male and female conspecifics and totals of up to sevenfold the number of males in the trap lures were caught overnight. Feeding males attracted more than double the number of conspecifics that responded to nonfeeding males. Active consumption of cucurbitacin in the plant on which the males were feeding, however, had no effect on attraction. A shift in sex ratio from a male to a female bias during field colonization season also supports the hypothesis that host finding is initiated by “pioneer” males. The importance of this aggregation pheromone in early-season host plant colonization and the evolutionary and adaptive significance of this pheromone are discussed.

Effects of Host Plant Phenology on Oviposition Preference of Crocidolomia pavonana (Lepidoptera: Pyralidae)

Abstract Field studies have demonstrated mixed success in trap cropping to manage Crocidolomia pavonana (=binotalis) [F.], a major pest of cruciferous crops in Asia. A possible explanation for this is an influence of host plant phenology on oviposition preference. We tested this in simultaneous two-choice oviposition bioassays under laboratory conditions. In cylindrical cardboard experimental arenas, with 5-cm2 leaf windows, individual C. pavonana females were offered eight sequential phenological stages of cabbage (Brassica oleracea L., Capitata group, cultivar Gloria) with a constant stage of preflowering Indian mustard (Brassica juncea, variety rugosa, cultivar Green Wave). Results showed a significant effect of cabbage developmental stage on oviposition preference. We continued with two-choice bioassays, using whole leaves, in screen cage experimental arenas. Females were offered the three most preferred phenological stages of cabbage and differing stages of four potential trap crop alternatives: preflowering Indian mustard; preflowering Chinese cabbage (B. rapa L., variety pekinensis [Lour.] Olsson); preflowering, flowering, and “with silique” sawi manis (B. rapa, variety parachinensis [Bailey] Tsen and Lee); and preflowering and flowering sayur pahit (B. rapa, variety parachinensis [Bailey] Tsen and Lee). Results indicated that the phenological stages of both plants had a significant effect on relative oviposition preference. However, patterns of preference changed in the context of the different plant species combinations. In addition, implicit hierarchical preference order was frequently contradicted. These results have implications for the improvement of trap cropping strategies to manage C. pavonana and for the potential success of biological control of Plutella xylostella [L.], where these pests occur in complex.

Effects of age, sex, and dietary history on response to cucurbitacin in Acalymma vittatum

The chrysomelid Acalymma vittatum is stenophagous, subsisting almost entirely on plants in the Cucurbitaceae, which generally contain cucurbitacins. Cucurbitacins are extremely bitter tetracyclic triterpenoids that are toxic to most organisms. As do other diabroticite beetles, A. vittatum sequester cucurbitacins, which have been shown to act as phagostimulants and arrestants. Our results reveal, however, that for A. vittatum the response to cucurbitacin diminishes with continued sequestration. Colony‐reared A. vittatum were fed only roots (as larvae) and foliage of either ‘Marketmore 76’ (which contains a normal amount of cucurbitacin, ‘bitter’) or ‘Marketmore 80’ (a near isogenic line that contains no cucurbitacin, ‘non‐bitter’) cucumber. Over 1200 individual beetles from the day of adult emergence to 15 days following emergence were placed in choice and no‐choice arenas containing potted cotyledons of the two cucumber varieties for 24 h. In choice tests, overall preference for the bitter cucumber cultivar was maintained, but degree of preference changed with age and became significantly less for beetles reared on bitter diets. Furthermore, in no‐choice tests, age, sex, dietary history, and interactions among these variables all significantly affected the feeding response to cucurbitacin. For A. vittatum reared without cucurbitacin, total consumption of the bitter cultivar increased over time. For beetles reared with cucurbitacin, total foliage consumption of the bitter cultivar declined, within nine days, to equal that of the non‐bitter cultivar. Feral A. vittatum, unexpectedly, consumed more of the non‐bitter than the bitter cultivar in no‐choice tests. Ecological and applied implications of this variation in response to cucurbitacin are discussed.

Larval Performance in Relation to Labile Oviposition Preference of Crocidolomia pavonana [F.] (Lepidoptera: Pyralidae) Among Phenological Stages of Cabbage

Abstract Crocidolomia pavonana (=binotalis) [F.] demonstrates oviposition peaks in the field that we believe to be correlated with host plant phenology. In previous two-choice laboratory experiments, we found the highest relative proportion of oviposition on cabbage to correspond either to plant growth stages ≈7–8 wk or ≈9–11 wk old, depending on the alternate host plant with which it was presented. In cabbage-only trials, leaves from 7- to 8-wk-old plants were preferred. Inconsistency in preference led to the question of whether oviposition on either cabbage growth stage would confer adaptive advantages in offspring performance. We simulated oviposition on four phenological stages of cabbage in two ways. In a study of complete immature development, growth rate, pupal weight, and survivorship were measured. We also compared food utilization efficiency during the fourth larval instar by analyzing growth rate, efficiency of biomass accumulation, and frass production by analysis of covariance (ANCOVA). For both experiments, cabbage plants of defined phenological stages were designated at the time of oviposition, and larvae were fed from these as plants continued to grow throughout larval development. Our data indicate adaptive advantages in larval growth rate and food conversion efficiency to oviposition on cabbage at ≈7–8 wk from planting. Oviposition on later cabbage growth stages resulted in comparatively poor larval performance. Possible explanations for C. pavonana oviposition behavior in light of these results are discussed.

Seasonal incidence of two co-occurring adult parasitoids of Acalymma vittatum in New York State: Centistes (Syrrhizus) diabroticae and Celatoria setosa

We report the incidence of striped cucumber beetle (Acalymma vittatum [Fabricius]) (Coleoptera: Chrysomelidae) parasitism in bi-weekly samples from diverse farm locations in central New York State over the course of two growing seasons. Two parasitoid species not previously verified in this geographic region were found: Celatoria setosa (Coquillett) (Diptera: Tachinidae) and Centistes (Syrrhizus) diabroticae (Gahan) (Hymenoptera: Braconidae). Parasitism by C. setosa, up to 43%, [mean 8.67%] was comparable to previously published rates. Contrary to the expectations of earlier authors, however, C. diabroticae was found to be ubiquitous and maximum rates of parasitism (~54%) were >threefold greater than the only other published report for this species [C. diabroticae mean 14.36%]. In laboratory assays, we investigated C. diabroticae larval development. We also tested the effects of wasp clone and host beetle sex on C. diabroticae larval development. This is the first documentation of life cycle information for this braconid.

Correspondence between rates of host plant consumption and responses to the Acalymma vittatum male-produced aggregation pheromone

Abstract In field studies, wind‐directed traps were used to investigate the resource‐based properties of the male‐produced aggregation pheromone of Acalymma vittatum (F.) (Coleoptera: Chrysomelidae). Responses to early season overwintered field‐collected male A. vittatum without food were compared with those feeding on pollen, and in turn these were compared with those feeding on cucurbit seedlings. These comparisons were modelled after transitions as they would occur at the initiation of A. vittatum host plant colonization.

Lady Beetles in New York: Insidious Invasions, Erstwhile Extirpations, and Recent Rediscoveries

Abstract Over the past 40 years, the complex of coccinellid (lady beetle or ladybug) species in New York has undergone substantial changes. Primarily, these changes have involved the decline of native species and the increase and spread of adventive species. Species declines have proceeded to the extent that several native species were feared to be extirpated from New York. Here we report that two of these native species, Adalia bipunctata (Two-spotted Lady Beetle) and Coccinella novemnotata (Nine-spotted Lady Beetle), were rediscovered in New York, in 2009 and 2011, respectively, by volunteers and specialists working for the Lost Ladybug Project. We found that the current coccinellid complex in New York is significantly less diverse and has a significantly higher proportion of foreign species compared to the complex in the past. We discuss the potential causes and implications for these shifts and rediscoveries.

The Status of Coccinella undecimpunctata (L.) (Coleoptera: Coccinellidae) in North America: An Updated Distribution from Citizen Science Data

Coccinella undecimpunctata L. is an Old World aphid predator that is native to central Asia, North Africa, Iceland, and much of Europe. The species was introduced accidently (Gordon 1985) and first reported in North America by Schaeffer (1912) based on two specimens from near Boston, Massachusetts. Since then, the species was found again in Massachusetts (Dobzhansky 1931), Vermont (Parker et al. 1976), Maine and New Jersey (Belicek 1976), and Ohio (Dailey et al. 1978) in the eastern USA and in Canada in New Brunswick, Prince Edward Island, and Quebec (Brown 1940), Nova Scotia and Newfoundland (Chapin 1956), and Ontario (Brown 1962). By the 1960s, C. undecimpunctata had also been found in the Pacific Northwest, near Seattle, Washington (Russell 1968), Vancouver, British Columbia (Belicek 1976) and Corvallis, Oregon (Wheeler and Hoebeke 1981). Wheeler and Hoebeke (1981) also added Connecticut, New York, Pennsylvania, and Rhode Island to update the distribution of C. undecimpunctata and noted the importance of this predator’s role in pest suppression. On Long Island, C. undecimpunctata had been found to represent 55% of all coccinellids found on potatoes (Day 1965). It has been proposed that C. undecimpunctata successfully extended its range with the help of the St. Lawrence Seaway as well as the railroad (Larochelle 1979; Watson 1979; Wheeler and Hoebeke 1981). But following a period of increase in the mid-20th century, the species appears to have declined to the point of extirpation from much of its former North American range. Wheeler and Hoebeke (2008) posed the question of whether or not C. undecimpunctata was still present in North America. Those authors reported that no additional USA states or Canadian provinces had been added to the distribution of C. undecimpunctata since the 1980s and documented the lack of recent records of C. undecimpunctata in Ontario, Québec, the Atlantic Provinces of Canada, New England, the midAtlantic states of Pennsylvania, Delaware, Maryland, and Virginia, and New York State. They suggested that C. undecimpunctata may persist in low numbers in some parts of the Northwest and Northeast of the USA, and in southwestern British Columbia and the eastern Maritime Provinces of Canada; they invited anyone who encountered this species to document the finding. Here we confirm the presence ofC. undecimpunctata in the Pacific Northwest and lend further evidence to its possible extirpation elsewhere in North America. Two C. undecimpunctata were located through postings to BugGuide.net – a continuing online collection of insect photographs curated by a community of naturalists. Twelve more C. undecimpunctata were located through submissions to the Lost Ladybug Project (www. lostladybug.org) a continent-wide coccinellid survey funded by the National Science Foundation since 2008. The Lost Ladybug Project is a webbased, citizen science program in which participants provide a digital photograph of the insect, contact information, location details, and habitat information via an online form. All specimens are photo-vouchered and identifications are made by researchers at Cornell University. During the five years between 2008 and 2012, the Lost Ladybug Project has received and identified over 20,000 photographic specimens. This relatively inexpensive method of data collection has permitted an abundance of data to be collected over a broad geographic range. Much as predicted by Wheeler and Hoebeke (2008), all 14 recently located C. undecimpunctata were found in the Pacific Northwest: Coquitlam, British Columbia; Puyallup and Bothell, Washington; Salem and Scio, Oregon. The Lost Ladybug Project has not received any reports from two eastern locations suggested by Wheeler and Hoebeke (2008) where C. undecimpunctata may persist: Sable Island and Brier Island, both in the Maritime Provinces of Canada.

The Influence of Exotic Lady Beetle (Coleoptera: Coccinellidae) Establishment on the Species Composition of the Native Lady Beetle Community in Missouri

Abstract The diversity and abundance of native lady beetles (Coccinellidae) in North America has declined in recent decades. This decline is often correlated with the introduction and establishment of exotic lady beetle species, including Coccinella septempunctata L. and Harmonia axyridis Pallas, suggesting that exotic species precipitated the decline of native lady beetles. We examined species records of native coccinellids in Missouri over 118 yr and asked whether the species composition of the community experienced a shift following the establishment of the exotic species. We found that the contemporary native coccinellid community is different from the community that was present nearly a century ago. However, there was no evidence for a recent abrupt shift in composition triggered by the establishment of exotic species. Instead, our data suggest that the native lady beetle community has been undergoing consistent and gradual change over time, with some species decreasing in abundance and others increasing. While not excluding exotic species as a factor contributing to the decline of native lady beetle species, our findings suggest that other continuous factors, like land use change, may have played a more influential role in determining the composition of the native coccinellid communities within our region.