Revision of Malagasy species of the genus Merma Weise (Coccinellidae: Epilachnini)

Malagasy Epilachnini are one of the least studied groups of the herbivorous ladybird beetles. Most of the species were described in the 19th and 20th centuries and their position within the modern classification has never been examined. Here we provide results of detailed study of two species Epilachna hovana Sicard, 1907 and Peralda quadriguttata, Sicard, 1909 which are proposed to be transferred to the genus Merma Weise (comb. nov.). Detailed morphological analysis, photographs of male and female genitalia and a key to species are also provided.

Revision of the genus Coccidula Kugelann (Coleoptera, Coccinellidae)

The genus Coccidula Kugelann includes five species distributed in the Holarctic, with one species in North America and four in Palearctic region. Coccidula belongs to the tribe Coccidulini which historically was treated as a separate subfamily within ladybird beetles, but recent studies confirmed its placement as a tribe within the broadly defined subfamily Coccinellinae. All species are revised and a new synonymy of Lithophilus naviauxi Duverger with C. litophiloides Reitter is proposed. Light and electron microscopy pictures support morphological descriptions. An identification key to all species is also provided.

Automatic ladybird beetle detection using deep-learning models

Fast and accurate taxonomic identification of invasive trans-located ladybird beetle species is essential to prevent significant impacts on biological communities, ecosystem functions, and agricultural business economics. Therefore, in this work we propose a two-step automatic detector for ladybird beetles in random environment images as the first stage towards an automated classification system. First, an image processing module composed of a saliency map representation, simple linear iterative clustering superpixels segmentation, and active contour methods allowed us to generate bounding boxes with possible ladybird beetles locations within an image. Subsequently, a deep convolutional neural network-based classifier selects only the bounding boxes with ladybird beetles as the final output. This method was validated on a 2, 300 ladybird beetle image data set from Ecuador and Colombia obtained from the iNaturalist project. The proposed approach achieved an accuracy score of 92% and an area under the receiver operating characteristic curve of 0.977 for the bounding box generation and classification tasks. These successful results enable the proposed detector as a valuable tool for helping specialists in the ladybird beetle detection problem.

CONTRIBUTIONS TO THE KNOWLEDGE OF THE LADYBIRD BEETLES (COLEOPTERA: COCCINELLIDAE) FROM THE FAUNA OF THE REPUBLIC OF MOLDOVA

The paper includes the fauna and ecology of ladybugs (Coleoptera: Coccinellidae) from various natural and agricultural ecosystems of the Republic of Moldova collected during 2008–2021 years and the specimens from the Museum of Entomology, Institute of Zoology collected between 1954–1979 years. In total, 23 species from 16 genera of Coccinellidae family were recorded.

Obstructs-equipped apparatus reduces cannibalism and improves larval survival of the Coccinellid, Harmonia axyridis (Coleoptera: Coccinellidae)

Background Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is an important biocontrol agent in native region of Asia, while its high propensity for cannibalism causes great obstacles in mass production. Provisioning obstructs in rearing containers could decrease the cannibalism of ladybird beetles. In this study, three different patterns of obstructs (Con-A, Con-B, and Con-C) were designed and equipped in plastic Petri dishes (95.38 cm3) as rearing units, and their efficiency for H. axyridis larval survival was tested. The potential of the high-density rearing was then evaluated using the optimal units with 16, 24, or 32 larvae per unit (named 16-L, 24-L, or 32-L, respectively). Results Larval survivals in obstructs-equipped units were generally higher than those in control, and significantly increased with the Con-C units (39.8% versus 74.2% at adult stage). With the Con-C units, the survivals were significantly higher at 16-L density (82.5%) than those at 24-L density (62.5%), but both were non-significantly different from those at 32-L density (70.0%). The weights of newly emerged adults (fit with the expected sex ratio of 1:1) at the higher densities were lower than those at 16-L density. Conclusions The results demonstrate that H. axyridis can be reared at a higher density (≈ 0.336 larvae/cm3) in a constrained unit and highlight the effects of obstructs in reducing cannibalism and improving insect survivals.

Evidence for intermolecular forces involved in ladybird beetle tarsal setae adhesion

Why can beetles such as the ladybird beetle Coccinella septempunctata walk vertically or upside-down on a smooth glass plane? Intermolecular and/or capillary forces mediated by a secretion fluid on the hairy footpads have commonly been considered the predominant adhesion mechanism. However, the main contribution of physical phenomena to the resulting overall adhesive force has yet to be experimentally proved, because it is difficult to quantitatively analyse the pad secretion which directly affects the adhesion mechanism. We observed beetle secretion fluid by using inverted optical microscopy and cryo-scanning electron microscopy, which showed the fluid secretion layer and revealed that the contact fluid layer between the footpad and substrate was less than 10–20 nm thick, thus indicating the possibility of contribution of intermolecular forces. If intermolecular force is the main physical phenomenon of adhesion, the force will be proportional to the work of adhesion, which can be described by the sum of the square roots of dispersive and polar parts of surface free energy. We measured adhesion forces of ladybird beetle footpads to flat, smooth substrates with known surface free energies. The adhesive force was proportional to the square-root of the dispersive component of the substrate surface free energy and was not affected by the polar component. Therefore, intermolecular forces are the main adhesive component of the overall adhesion force of the ladybird beetle. The footpads adhere more strongly to surfaces with higher dispersive components, such as wax-covered plant leaves found in the natural habitat of ladybird beetles. Based on the present findings, we assume ladybird beetles have developed this improved performance as an adaptation to the variety of plant species in its habitat.