Search Results (7)

As a social organism, living in a communal structure is one of the most important physical barriers against environmental elements and natural enemies. Thaumetopoea pityocampa (Notodontidae, Thaumetopoeinae) caterpillars are conifer pests that spend most of their larval stage in winter. Although T. pityocampa holds economic and medical significance, the tent construction and foraging behaviour are poorly understood. We observed the tent construction behaviour in autumn (October and November) when third- and fourth-instar T. pityocampa caterpillars build the ‘winter tent’ that can withstand winter conditions. Just before sunset, with no rain and temperatures over 12 °C, tent construction was undertaken by early active individuals, primarily larger male caterpillars. Early active caterpillars emerge from the tent first and spin silk on the tent for expansion and strength. Once temperatures dropped below 12 °C and twilight had passed, the early active caterpillars went out to forage and were later joined by the late active caterpillars, which were predominantly smaller females that had remained inside the tent. Foraging behaviour was continuously monitored for the first to fourth larval instars in the field. Foraging was more frequent in younger instars when environmental temperatures were warmer and became continuous and prolonged in later instar caterpillars as temperatures dropped. The final tent structure built by later instar caterpillars had the thickest layer of silk on the southern side of the tent compared to other orientations to receive maximum solar radiation during the winter. Our study provided additional insights into the collective nest building, foraging and social behaviours observed in Lepidoptera, as well as the roles of individuals within non-eusocial insect colonies. Full article

The ‘mother knows best’ hypothesis is tested in a species of processionary moth feeding on acacias and eucalypts in Australia. The processionary moth Ochrogaster lunifer (Lepidoptera: Notodontidae; Thaumetopoeinae) is a social caterpillar living in large colonies on a number of tree and shrub species. Five nesting types—canopy, trunk, tree-hugger, hanging, and ground—have been described, and this study deals with canopy nesters on various species of acacias (Acacia spp.) and eucalypts (Eucalyptus spp. and Corymbia spp.). Reciprocal transplant experiments conducted over three years confirm the ‘mother knows best’ hypothesis, as colonies performed better on the natal host plant than on the recipient ones. Young first instar larvae were less likely to establish on a non-natal host than the mature larvae, and all acacia-sourced canopy egg masses failed to establish on eucalypts. Large larvae were able to establish on transplant hosts. This suggests a strong preference–performance link at what is likely a species level, confirming preliminary results recently published on genetic divergence. Canopy nesting forms also have a lower realised fecundity than the ground nesting form on acacias from the same geographic area, but higher than another canopy nesting form from western Australia. Further observations on ecological and genetic traits are required to draw conclusions about the separation of lineages in the canopy nesting form of O. lunifer, by including populations from other parts of the range for both the herbivore and the host plants. Full article

Caterpillars of the Alcon blue butterfly Phengaris alcon are initially endophytic and feed inside the flowerheads of Gentiana plants, but complete their development as social parasites in the nests of Myrmica ants, where they are fed by workers. Its specific and complicated ecological requirements make P. alcon a very local, threatened species, sensitive to environmental changes. We investigated an isolated and previously unknown population in an area of high nature value—the Białowieża Forest (NE Poland). Using the mark–release–recapture method we estimated the seasonal number of adults at 1460 individuals, and their density (850/ha) was the highest among all populations using G. pneumonanthe studied so far. The site is also unique due to the presence of the specific parasitoid Ichneumon cf. eumerus, and parasitoids are considered the ultimate indicators of the biodiversity of Phengaris systems. Since 75.5% of P. alcon pupae were infested we could estimate the seasonal population of adult wasps at about 4500 individuals. The high abundance of both P. alcon and its parasitoid may be explained by favorable habitat characteristics, i.e., the strong presence of host plants and the high density of nests of Myrmica scabrinodis, which is the only local host ant of the butterfly. Full article

The socially parasitic Alcon blue butterfly (Phengaris alcon) starts its larval stage by feeding on the seeds of gentians, after which it completes development in the nests of suitable Myrmica ant species. The host plant and host ant species can differ at the population level within a region, and local adaptation is common, but some host switches are observed. It has been suggested that one mechanism of change is through the re-adoption of caterpillars by different ant species, either through occupation of abandoned nests or take-over of established nests by competitively superior colonies. To test this question in the lab we introduced relatively strong colonies (50 workers) of alien Myrmica species to the arenas of weaker colonies (two caterpillars with six workers), and to orphaned caterpillars (two caterpillars without ants). We used caterpillars from a xerophylic population of P. alcon, and both local hosts, M. sabuleti and M. scabrinodis, testing the possibility of host switch between these two host ant species during larval development. Most of the caterpillars were successfully readopted by alien ants, and survived well. Our results suggest higher ecological plasticity in host ant usage of this butterfly than generally thought. Full article

Oak processionary moth (Thaumetopoea processionea) or OPM was accidentally introduced into London on imported oak trees and now poses a threat to the future of oak in the urban landscape. Early attempts at eradication of the moth failed and significant resources have since been spent by government on monitoring and controlling OPM (through the use of insecticides or bio-pesticides) as it spreads into new areas. OPM is regulated in the UK to minimize risk of new introductions and reduce spread. Surveying for OPM and issuing of statutory notices for control is based on a geographical system of core, control and protected zones. While OPM will defoliate the trees leaving them vulnerable to other pests and diseases and stress factors, the caterpillars can also harm people and animals via tiny urticating hairs with the potential for dermatological or respiratory impacts. However, the biggest threat to the iconic British oak may be that the perceived risks associated with OPM, and costs of management may lead land managers to fell their oak trees, and not plant oak in the future. There is a need to better understand awareness, risk perceptions and decision-making around OPM management. We use a conceptual framework to explore decision-making and the trade-offs between the social, economic and ecological values associated with oak trees, and assessment of risk related to both the moth and control options. Twenty nine interviews were conducted in two London boroughs and across Greater London and in some surrounding counties covering a range of land types (e.g., parks, school grounds, amenity areas and private gardens) with infested or non-infested oak. We found a lack of evidence of human health impacts from OPM although land managers were concerned about public duty of care and potential reputational damage if they do not manage OPM. To address the challenges of dealing with OPM, land managers were taking a risk-based approach and managing OPM where it posed the highest potential risk to people. Respondents expressed strong emotional attachments to oak but it also has high biodiversity value which can lead to difficult decisions about management options. A risk-based approach moves beyond a ‘one-size-fits-all’ control method and focuses available resources where they are most needed and socially acceptable. An approach that allows for multiple values and perspectives on risk may provide a more sustainable long-term option for OPM management to ensure the future of oak in the city. Full article

In environments undergoing constant transformation due to human action, such as deforestation and urbanization, the emergence of pests has become a challenge for agriculture and human welfare. In Brazil, over a thousand tonnes of pesticides are used annually, causing serious environmental damage such as the decline of insect populations. It is necessary to search for control alternatives in order to reduce the environmental impact caused by insecticides. This review aims to describe the use of social wasps as agents of biological control, focusing on the perspectives of their use in small farms and urban gardens, and to discuss the benefits of using this method. Studies have shown that 90–95% of the prey captured by wasps in small crops is made of leaf-eating caterpillars. In urban gardens, wasps diversify their prey, among which potential disease vectors, such as dipterans, stand out. We outline techniques for managing social wasp colonies in small farm and urban garden settings, including the use of artificial shelters. Among the advantages of using wasps as control agents, we highlight the practicality of the method, the low operational cost, the absence of prey resistance and the decrease of the use of insecticides. Full article

The behavioral biology of the first instar larva of Cactoblastis cactorum was studied from the time of eclosion until the colony penetrated and initiated excavation of the host plant. Hatching from an egg stick was asynchronous, requiring 20 h for the entire cohort to eclose at 50%–70% RH and significantly longer at a lower range of RHs. On eclosion, neonates aggregated in an arena at the base of their egg stick and did not attempt to excavate the cladode until an average of 25 caterpillars had collected, approximately 15 h after the onset of egg hatch. Typically only a single entrance hole was formed, limiting the active process of excavating to one or a few individuals at-a-time until the host was fully penetrated and enlarged internally. Olfactometer tests showed that the neonates are strongly attracted to volatile chemicals released when caterpillars chewed into the cladode, accounting for the strong fidelity of the whole cohort to the initial site of penetration. In one instance, the caterpillars were observed to deal with an explosive release of mucilage by imbibing the liquid until the flooded zone was drained and the caterpillars could reenter the plant through the original entrance hole. Once inside the cladode, marked individuals adopted a regular cycle of defecating at the surface at a mean interval of approximately 10 min when followed for 35 successive cycles. Blanket spraying cladodes with a mandibular gland extract prior to hatching led to the independent dispersal of neonates and a failure to form an arena. When the cladode was impenetrable at the site of eclosion, the active cohort of unfed neonates set off together in search of a new site, marking and following a persistent trail that allowed late-to-eclose caterpillars to join their departed siblings. The adaptive significance of these observations is discussed in the context of the life history of the caterpillar. Full article