Bark Bugs Research Articles

Synopsis of the remarkable family Phloeidae (Hemiptera: Pentatomoidea): species identification, chromatic polymorphism and updated distribution

ABSTRACT The Neotropical family Phloeidae includes three species within two genera, Phloea Lepeletier and Serville, 1825 and Phloeophana Kirkaldy, 1908, distributed in South America. Due to their large size and notable morphological features, such as cryptic colouration, extreme body flattening and lateral expansions around the body, these insects became known as Neotropical bark bugs. These characteristics also make them easily recognisable; nonetheless, the correct identification of the species is still tricky, even more so for the nymphs. In this work, we clarify the identity of the species, present new diagnoses for the family, both genera and all species, and provide an updated identification key to both adults and nymphs of the three species. We also describe and illustrate chromatic variation in Phloea subquadrata Spinola, 1837, and high-resolution photos of the three species and important diagnostic characters are provided. Literature information is synthesised and updated, and an exhaustive synonymic list is provided for the three species, including two nomenclatural corrections: Phloeocoris paradoxus Burmeister, 1835 is removed from synonymy with Phloeophana longirostris (Spinola, 1837) and considered a new junior synonym of Phloea corticata (Drury, 1773); and Phlaea paradoxa Signoret, 1863 is removed from synonymy with Phloea corticata and considered a new junior synonym of Phloeophana longirostris. Lastly, we review the distribution of the species based on collection specimens and citizen science data and, for the first time, present distribution maps for the three species of Phloeidae.

Wiederbesiedlung der Waldbrandfläche von Leuk durch Gliederfüsser

Arthropod recolonization after the forest fire in Leuk The forest fire of Leuk (Wallis) in 2003 offered the opportunity to assess the impact of fire on arthropods and their succession after the event. We used standardized traps to sample arthropods in the center and at the edge of the burned area as well as in the intact forest outside the surface, two, three, five and ten years after the fire. We investigated different taxonomic and functional groups with particular focus on deadwood dwelling and endangered beetle species. We sampled 1898 species: 949 exclusively within the burned area and 159 exclusively in the intact forest. While the species number in the intact forest hardly changed during the investigation period, it increased dramatically in the burned area immediately after the fire. This was true for the herbivores and pollinators, as well as for the deadwood dwelling and endangered beetle species. In contrast, the number of species in two ground-dwelling groups, i.e., spiders (predators) and woodlice (decomposers), in the burned area exceeded those of the intact forest plots only five or ten years after the fire. During the first three years after the fire, we also sampled pyrophilic (fire-adapted) species, such as the bark bug Aradus lugubris and the longhorn beetles Acmaeops septentrionis and A. marginatus in the burned area. In total, there were 285 indicator species of specific and 38 further indicator species of unspecific post-fire successional stages. In contrast, only 18 indicator species of intact forests could be found. As such, forest fire is an ecological disturbance that can be considered as an important driver for maintaining and enhancing biodiversity as well as fire-specialized species.

Mimicking bug-like surface structures and their fluid transport produced by ultrashort laser pulse irradiation of steel

Ultrashort laser pulses with durations in the fs-to-ps range were used for large area surface processing of steel aimed at mimicking the morphology and extraordinary wetting behaviour of bark bugs (Aradidae) found in nature. The processing was performed by scanning the laser beam over the surface of polished flat sample surfaces. A systematic variation of the laser processing parameters (peak fluence and effective number of pulses per spot diameter) allowed the identification of different regimes associated with characteristic surface morphologies (laser-induced periodic surface structures, i.e., LIPSS, grooves, spikes, etc.). Moreover, different laser processing strategies, varying laser wavelength, pulse duration, angle of incidence, irradiation atmosphere, and repetition rates, allowed to achieve a range of morphologies that resemble specific structures found on bark bugs. For identifying the ideal combination of parameters for mimicking bug-like structures, the surfaces were inspected by scanning electron microscopy. In particular, tilted micrometre-sized spikes are the best match for the structure found on bark bugs. Complementary to the morphology study, the wetting behaviour of the surface structures for water and oil was examined in terms of philic/phobic nature and fluid transport. These results point out a route towards reproducing complex surface structures inspired by nature and their functional response in technologically relevant materials.

(E)-4-Oxo-2-hexenal Dimers in the Scent Glands of the Bark BugPhloea subquadrata(Heteroptera, Phloeidae)

Bark bugs belonging to the family Phloeidae are known for their camouflage on tree trunks. The nymphs store in dorsal abdominal glands defensive secretions with a pungent odor mainly constituted of (E)-2-hexenal, (E)-2-octenal, and (E)-4-oxo-2-hexenal. The metathoracic glands of adults (male and female) store (E)-2-hexen-1-ol and (E)-2-hexenyl acetate, which are less irritating than their corresponding aldehydes. Additional compounds of m/z 224 were detected in the scent glands of these insects and were previously suggested to be dimers of the (E)-4-oxo-2-hexenal. Thus, the aim of this study was to elucidate the details of the chemical structure of the dimers found in the scent glands of Phloea subquadrata. These dimers were obtained by synthesis and were compared with the natural products, confirming the dimeric structures of the latter. These (E)-4-oxo-2-hexenal dimeric compounds are novel and have not been reported before.

Genetic differentiation in sympatric but temporally isolated pine bark bugs, Aradus cinnamomeus (Heteroptera)

The pine bark bug Aradus cinnamomeus is a Eurasian insect pest of Scots pine. Each generation lives for two years in most areas in Europe, but in the north and in the Aland archipelago the generation time is three years. In western Finland, the 2-year bugs reproduce mainly in odd years, while in eastern Finland (as well as in eastern Sweden) the even-year generation predominates. Odd-year bugs are very rarely found in the even-year area, and even-year bugs are very rarely found within the odd-year area. The existence of sympatric but isolated alternate-year generations offers a possibility to study the effect of ecological genetic factors in a natural test situation since all environmental variables should be otherwise identical. In the north and in the Aland archipelago, the preponderance of one generation is not so pronounced, and three generations usually coexist in almost equal numbers. The Finnish parapatric odd and even-year generations (which are in the majority) are genetically virtually identical, while the odd and even-year minority generations deviate genetically (and morphologically) from the majority ones. In the three-year area the sympatric but allochronic bug generations differ genetically from each other to about the same extent as the allopatric but synchronic populations differ from each other. The sympatric differentiation can be explained as being a result of within species competition, although several other possible explanations exist. Furthermore, the two-year bugs collected from eastern Sweden appeared to diverge genetically, although they represent the locally predominating generation.

New data on distribution of bark bugs in Siberia and the Far East of Russia (Heteroptera: Aradidae)

New data are given on distribution of 17 species of Aradus in 15 administrative regions of Siberia and the Far East of Russia.

Anatomical Symptoms in the Wood of Scots Pine Damaged by Frost and Pine Bark Bugs

This study deals with the comparison of damage caused by frost and pine bark bugs (Aradus cinnamomeus Panzer) to the anatomical wood structure of Scots pines (Pinns sylvestris L.). Both damages are typical of pine saplings in a dry heath forest. A scanning electron microscope was used in identifying the damages.The location and manner of manifestation of the frost and pine bark bug damage differed from one another. The anatomical symptoms of the two types of damage in the annual rings were very similar to one another. However, the identification of frost damage is made easier by the collapsed appearance of the cells and the considerable accumulation of cell wall material to the damaged areas. The abnormal wood structure may disturb the water and nutrient transport in trees.

Nutritional disturbances of young Scots pines caused by pine bark bugs in a dry heath forest

This study deals with the effect of pine bark bugs (Aradus cinnamomeus Panzer) on the nutrition of young Scots pines (Pinus sylvestris L.). Soil and needle samples for analytical purposes were collected from a young pine stand growing on a dry barren mineral soil afflicted by pine bark bugs.

Morphological Variation in Aradus cinnamomeus (Heteroptera): Geographic Patterns and Character Displacement

Morphological variation in the pine bark bug Aradus cinnamomeus Panzer was studied in 43 metric measurements of the head, thorax and abdomen of adult males and 40 of females. The extent of geographic variation in males and females was studied among Finnish two-year bug populations, 14 of which belonged to the eastern even-year reproducing cohort and 11 to the western odd-year cohort. These allochronic cohorts have a parapatric distribution. The first three dimensions obtained in canonical discriminant analysis together accounted for 57% of the variation present in the males and 60% in the females, respectively. The first three canonical variables were statistically significantly correlated in both sexes with the latitude and longitude of the locality. The alternate-year cohorts formed two separate groups of populations. The closer the allochronic bugs originated to each other, the greater the morphological difference between them. The possibility of intraspecific character displacement is discussed in this context, and a new definition is presented for the concept of character displacement including within-species cases.

Morphological variation in Aradus cinnamomeus (Heteroptera: Aradidae): patterns within parapatric alternate-year populations

AbstractMorphological variation in the pine bark bug Aradus cinnarnomeus Panzer was studied by making 43 metric measurements of the head, thorax and abdomen of adult males and 40 of the females (n = 1884). The amount of individual variation in males and females was studied both in pooled bug material and separately in two parapatric alternate-year cohorts, i.e. in the Finnish eastern even-year and the western odd-year reproducing populations. The first three dimensions in a principal components analysis accounted for 36% of the variation present in males in the pooled data and for 43% of the variation in females, respectively. There appeared to be different trends in individual variation within the western odd-year cohort and within the eastern even-year cohort. The first principal component describes the general size of the bug in all analyses, while the second and third components correlate best with different measurements depending on the sex and the cohort examined.

Heavy metal levels in two biennial pine insects with sap-sucking and gall-forming life-styles

The concentrations of cadmium, copper, nickel and lead were studied in two biennial pine insects in relation to the deposition of heavy metals in the environment around the industrialised town of Harjavalta in southwestern Finland. Sap-sucking pine bark bugs, Aradus cinnamomeus (Heteroptera, Aradidae), and gall-forming pine resin gall moths, Petrova resinella (Lepidoptera, Tortricidae) were collected on sample plots located at logarithmic distances along 9 km-long transects from the distinctive emission source. The responses of these insects representing different life-style were compared. Heavy metal concentrations in A. cinnamomeus were highest (Cd 17 μg g −1, Cu 1900 μg g −1, Ni 220 μg g −1, Pb 32 μg g −1) in the vicinity of the factor complex, and lowest in the outermost zones. This trend followed a linear regression model. The pattern was less clear in P. resinella, the concentrations being only one-tenth of those recorded in A. cinnamomeus. Correlations between metal levels in A. cinnamomeus and previously examined Sphagnum moss bags proved to be highly significant in every case. The differences in the heavy metal concentrations of these two insect species, which occupy the same trophic position, would appear to be due to the differences in their feeding characteristics. Heavy metals accumulate in the posterior bulb of the midgut in the discontinuous alimentary system of A. cinnamomeus, while P. resinella is likely to secrete most of the metals into the walls of the galls. The almost total absence of these two insect species near the factory complex seems to be associated with the high concentrations of metals.

Bugs in Bags: Intraspecific Competition Affects the Biogeography of the Alternate-Year Populations of Aradus cinnamomeus (Heteroptera)

Aradus cinnamomeus, a pest of pines, shows a two-year life cycle with two widely distributed parapatric alternate-year populations and a narrow overlap zone in southern Finland. To explain the dynamics of this unique biogeographical pattern the intraspecific competition hypothesis was tested by field experiments involving crowding, transplantation and mixing the two reproductively isolated populations. The study was carried out simultaneously in both the evenand odd-year populations areas (defined according to the reproduction year of the locally dominant population) and in the narrow overlap zone. In addition to the mortality of both age-classes, the growth rate of larvae and the adult size were studied in the tests. The results suggest that younger larvae are better exploitation competitors than older larvae or adults. They can penetrate deeper into smaller crevices in the bark than the larger bugs, and thus exploit a wider range of resources. However, exploitation (within test bags) competition plays only a minor role in the regulation of the biogeographic pattern of the pine bark bug. The presence of the natural background population in the test trees (mostly outside the test bags) increased the mortality of the transplantated bugs of the other age-class to about the same extent as on a highly unfavourable site. Interference competition between the two age-classes, reinforced by the impact of exploitation competition and parasitism, can reasonably well explain the parapatry of the alternate-year populations, although direct evidence for interference is still lacking.

Camouflage by Integumentary Wetting in Bark Bugs

Unlike most insect integuments, the body surfaces of certain bark-inhabiting bugs are wettable. A thin film of water reduces the reflectivity of the insect, resulting in a close match with the wettable bark upon which it rests. Wettability probably aids in concealing the insects from predators.

Morphology of the Neurosecretory System and the Retrocerebral Endocrine Glands of Adult Halys dentatus (Heteroptera: Pentatomidae)1

The neurosecretory system of the bark bug, Halys dentatus F., was studied with aldehyde fuchsin and performic acid-victoria blue techniques. Two groups of cells, each group with 6–7 “Type A” neurosecretory cells, and their neurosecretory pathways are described. “Type B” fells are probably absent in this insect. The nervi corporis 1 run ventrolateral to the corpus cardiacum and innervate the aortal wall after bypassing the gland. Neurosecretory material is present, in the aortal wall, in the axons of the nervi corporis 1, and not in the intercellular spaces. In H. dentatus, neurosecretory material is stored and released from the axons of the nervi corporis 1 and not from the aortal wall.