Immature Insect Assemblages from the Early Cretaceous (Purbeck/Wealden) of Southern England

The record of immature insects from the non-marine Purbeck and Wealden groups (Lower Cretaceous) of southern England is reviewed and expanded. Fossils of adult terrestrial insects are locally common, but terrestrial immature remains are restricted to transported hemipterans, most of which are sessile nymphs or puparia resembling those of extant whiteflies (Aleyrodidae). Remains of immature aquatic insects are more diverse and comprise the extant orders Plecoptera, Ephemeroptera, Odonata, Trichoptera, Hemiptera and Diptera. The Trichoptera are represented by larval cases constructed from a variety of materials corresponding to several ichnogenera. The Wealden immature insects were preserved in predominantly freshwater fluvial settings, whereas the Purbeck ones occur in lagoonal palaeoenvironments, ranging in salinity from brackish to hypersaline. The composition of aquatic immature insect faunas in the latter offers potential for palaeosalinity analysis, although there are complicating factors relating to habitat stability. Uncommon trace fossils such as beetle borings in wood provide evidence of immature insects not represented by body fossils.

Bacteria cultured from the gut of Meccus pallidipennis (Hemiptera: Reduviidae), a triatomine species endemic to Mexico

The study of intestinal microbiota in vector insects like triatomines is paramount in parasitology because many parasitic species inhabit the vector's gut. Although knowledge on the gut microbiota in various vectors of the parasitic flagellate Trypanosoma cruzi has grown, research efforts have focused on South American triatomines. This study reports the isolation of bacterial microbiota in the anterior and posterior gut of Meccus pallidipennis (a triatomine species endemic to Mexico) by culture, as well as its identification by phenotypic and biochemical tests and its quantification by counting colony-forming units. The study was performed on fifth-instar nymph and adult specimens of M. pallidipennis, either laboratory-bred or collected in the field and either infected or not with T. cruzi. Overall, 17 bacterial species were identified, with the genera Bacillus and Staphylococcus being the most prevalent regardless of the origin of the insects. No differences were observed in the number of bacterial species in the gut of laboratory-bred and field-collected insects, neither with respect to life stage or infection status. In general, the Shannon-Weaver diversity index was higher in non-infected insects than in infected ones. Further studies using non-culture methods are required to determine whether bacterial species diversity is modified by laboratory breeding.

Aberrant ontogeneses and life cycles in Paraneoptera

The paper is a third part of the themed issue "Aberrant cytogenetic and reproductive patterns in the evolution of Paraneoptera", prepared by a Russian-Bulgarian research team on the basis of long-term collaborative studies. This chapter reviews different peculiar aberrations in the ontogenesis of Paraneoptera, such as the appearance of the quiescent apodal and/or arostrate instars, exuviatrial, pupillarial and pseudopupillarial development, cyclic parthenogenesis, etc. The material and methods, terminology and the nomenclature of the used taxonomic names are listed in the first chapter of the issue (Gavrilov-Zimin et al. 2021).

Evaluating Transmission Paths for Three Different Bartonella spp. in Ixodes ricinus Ticks Using Artificial Feeding

Bartonellae are facultative intracellular alpha-proteobacteria often transmitted by arthropods. Ixodes ricinus is the most important vector for arthropod-borne pathogens in Europe. However, its vector competence for Bartonella spp. is still unclear. This study aimed to experimentally compare its vector competence for three Bartonella species: B. henselae, B. grahamii, and B. schoenbuchensis. A total of 1333 ticks (1021 nymphs and 312 adults) were separated into four groups, one for each pathogen and a negative control group. Ticks were fed artificially with bovine blood spiked with the respective Bartonella species. DNA was extracted from selected ticks to verify Bartonella-infection by PCR. DNA of Bartonella spp. was detected in 34% of nymphs and females after feeding. The best engorgement results were obtained by ticks fed with B. henselae-spiked blood (65.3%) and B. schoenbuchensis (61.6%). Significantly more nymphs fed on infected blood (37.3%) molted into adults compared to the control group (11.4%). Bartonella DNA was found in 22% of eggs laid by previously infected females and in 8.6% of adults molted from infected nymphs. The transovarial and transstadial transmission of bartonellae suggest that I. ricinus could be a potential vector for three bacteria.

Collection of immature Dermacentor reticulatus (Fabricius, 1794) ticks from vegetation and detection of Rickettsia raoultii in them

It is commonly assumed that Dermacentor reticulatus immature life stages are nidicolous and therefore cannot be collected from vegetation. However, in June and July of 2018 and 2019, a total of 47 questing D. reticulatus larvae and two nymphs were collected by the flagging method in two different sites close to the city of Leipzig, Germany. To confirm their role in the transmission of tick-borne pathogens, 45 larvae (pooled by 2 in 21 pools and 1 pool with three individuals) and one nymph were tested either by conventional or real-time PCR for the presence of Bartonella spp., Neoehrlichia mikurensis, Rickettsia spp., and Babesia spp. All samples tested negative for Bartonella spp., N. mikurensis, and Babesia spp.; while the minimal infection rate of larvae for Rickettsia spp. was 42%, and the one tested nymph was also positive. Sequencing partial ompB genes revealed the presence of Rickettsia raoultii in larvae and nymph. Further research needs to be done to determine under which circumstances immature D. reticulatus ticks are found outside the burrows of their hosts and can be collected from vegetation.

Long-term exposure of cockroach Blaptica dubia (Insecta: Blaberidae) nymphs to magnetic fields of different characteristics: effects on antioxidant biomarkers and nymphal gut mass

Purpose: The main goal of this study was to analyze the long-term effects of static (SMF) and extremely low-frequency magnetic field (ELF MF) on nymphal gut mass and antioxidant biomarkers in this tissue of cockroach Blaptica dubia. Materials and methods: One-month-old nymphs were exposed to magnetic field (MF) for 5 months in three experimental groups: control, exposure to SMF (110 mT) and exposure to ELF MF (50 Hz, 10 mT). Results: The gut masses of the MF groups were significantly lower when compared to control. Superoxide dismutase (SOD) and catalase (CAT) activities were markedly higher than for the control and the differences between the MF groups were statistically significant only for SOD. The applied MF had no effect on total glutathione (GSH) content. Glutathione reductase (GR) and glutathione S-transferase (GST) activities were significantly lower in both MF groups in comparison to the control. There was a significant difference between MF groups for GR activity. Principal Component Analysis (PCA) showed that CAT and GST were the main factors contributing to the differentiation of the control group from the treated experimental groups along PCA 1, and SOD and GR along PCA 2. PCA revealed clear separation between experimental groups depends on antioxidant biomarker response. Conclusion: The applied magnetic fields could be considered a potential stressor influencing gut mass, as well as examined antioxidative biomarkers.

Olfactory Response of the Predatory Bug Orius laevigatus (Hemiptera:Anthocoridae) to the Aggregation Pheromone of Its Prey, Frankliniella occidentalis (Thysanoptera: Thripidae)

Herbivore natural enemies base their foraging decision on information cues from different trophic levels but mainly from plant odors. However, the second trophic level (i.e., the herbivorous prey) may also provide reliable infochemical cues for their natural enemies. We have evaluated the role of the aggregation pheromone from Frankliniella occidentalis (Pergande) as a potential kairomone for its natural enemy, the predatory bug Orius laevigatus (Fieber). For this purpose, we have analyzed the response of O. laevigatus to (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate, the two major components of the thrips aggregation pheromone. These compounds have been offered to O. laevigatus adult females and nymphs of the predatory bugs both in separate and as specific (1:1 or 1:2.3) blends, in experiments involving a dual choice Y-tube olfactometer. None of the compounds attracted adults or nymphs when they were individually supplied. Conversely, they were significantly attracted to both adults and nymphs when offered as a blend. A 1:2.3 (R)-lavandulyl acetate:neryl (S)-2-methylbutanoate blend was attractive to both nymphs and adults, while a 1:1 blend elicited response only in nymphs. These results suggest that specific blends of these compounds from the aggregation pheromone may be used as an attractant to O. laevigatus. The results of this work highlight the importance of studying olfactory responses of natural enemies for a better understanding of their foraging behavior. Potential uses of these results in future studies are discussed.

Haemaphysalis longicornis Ticks as Reservoir and Vector of Severe Fever with Thrombocytopenia Syndrome Virus in China

Transstadial and transovarial virus transmission occur among ticks, and transmission to mice can occur through a tick bite.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging hemorrhagic fever in East Asia caused by SFTS virus (SFTSV), a newly discovered phlebovirus. The Haemaphysalis longicornis tick has been suspected to be the vector of SFTSV. To determine whether SFTSV can be transmitted among ticks, from ticks to animals, and from animals to ticks, we conducted transmission studies between developmental stages of H. longicornis ticks and between ticks and mice. Using reverse transcription PCR, we also analyzed the prevalence of SFTSV infection among H. longicornis ticks collected from vegetation in Shandong Province, China. Our results showed a low prevalence of SFTSV among collected ticks (0.2%, 8/3,300 ticks), and we showed that ticks fed on SFTSV-infected mice could acquire the virus and transstadially and transovarially transmit it to other developmental stages of ticks. Furthermore, SFTSV-infected ticks could transmit the virus to mice during feeding. Our findings indicate ticks could serve as a vector and reservoir of SFTSV.

Evolution of insect wings and development - new details from Palaeozoic nymphs

The nymphal stages of Palaeozoic insects differ significantly in morphology from those of their modern counterparts. Morphological details for some previously reported species have recently been called into question. Palaeozoic insect nymphs are important, however - their study could provide key insights into the evolution of wings, and complete metamorphosis. Here we review past work on these topics and juvenile insects in the fossil record, and then present both novel and previously described nymphs, documented using new imaging methods. Our results demonstrate that some Carboniferous nymphs - those of Palaeodictyopteroidea - possessed movable wing pads and appear to have been able to perform simple flapping flight. It remains unclear whether this feature is ancestral for Pterygota or an autapomorphy of Palaeodictyopteroidea. Further characters of nymphal development which were probably in the ground pattern of Pterygota can be reconstructed. Wing development was very gradual (archimetaboly). Wing pads did not protrude from the tergum postero-laterally as in most modern nymphs, but laterally, and had well-developed venation. The modern orientation of wing pads and the delay of wing development into later developmental stages (condensation) appears to have evolved several times independently within Pterygota: in Ephemeroptera, Odonatoptera, Eumetabola, and probably several times within Polyneoptera. Selective pressure appears to have favoured a more pronounced metamorphosis between the last nymphal and adult stage, ultimately reducing exploitation competition between the two. We caution, however, that the results presented herein remain preliminary, and the reconstructed evolutionary scenario contains gaps and uncertainties. Additional comparative data need to be collected. The present study is thus seen as a starting point for this enterprise.

Climate of origin affects tick (Ixodes ricinus) host-seeking behavior in response to temperature: implications for resilience to climate change?

Climate warming is changing distributions and phenologies of many organisms and may also impact on vectors of disease-causing pathogens. In Europe, the tick Ixodes ricinus is the primary vector of medically important pathogens (e.g., Borrelia burgdorferi sensu lato, the causative agent of Lyme borreliosis). How might climate change affect I. ricinus host-seeking behavior (questing)? We hypothesize that, in order to maximize survival, I. ricinus have adapted their questing in response to temperature in accordance with local climates. We predicted that ticks from cooler climates quest at cooler temperatures than those from warmer climates. This would suggest that I. ricinus can adapt and therefore have the potential to be resilient to climate change. I. ricinus were collected from a cline of climates using a latitudinal gradient (northeast Scotland, North Wales, South England, and central France). Under laboratory conditions, ticks were subjected to temperature increases of 1°C per day, from 6 to 15°C. The proportion of ticks questing was recorded five times per temperature (i.e., per day). The theoretical potential to quest was then estimated for each population over the year for future climate change projections. As predicted, more ticks from cooler climates quested at lower temperatures than did ticks from warmer climates. The proportion of ticks questing was strongly associated with key climate parameters from each location. Our projections, based on temperature alone, suggested that populations could advance their activity season by a month under climate change, which has implications for exposure periods of hosts to tick-borne pathogens. Our findings suggest that I. ricinus have adapted their behavior in response to climate, implying some potential to adapt to climate change. Predictive models of I. ricinus dynamics and disease risk over continental scales would benefit from knowledge of these differences between populations.

Comparative morphology of immature stages of four species of Chinavia (Hemiptera, Pentatomidae), with a key to the species of Rio Grande do Sul, Brazil

Chinavia Orian (1965) is one of the most diverse genera of Pentatomidae, distributed in the Afrotropical, Neotropical and Nearctic Regions. Thirty-two species are recorded for Brazil, some of them having potential economic impact because they are found on crops and referred to as pests. The morphology of the five nymphal instars of Chinavia armigera (Stål, 1859), Chinavia aseada (Rolston, 1983), Chinavia brasicola (Rolston, 1983) and Chinavia runaspis (Dallas, 1851) are described here. Through a comparative study, identification keys were developed to allow an early identification of the 12 Chinavia species of Rio Grande do Sul.

Horizontal and vertical movements of host-seeking Ixodes pacificus (Acari: Ixodidae) nymphs in a hardwood forest

The nymph of the western black-legged tick (Ixodes pacificus) is an important bridging vector of the Lyme disease spirochete (Borrelia burgdorferi) to humans in the far-western United States. The previously unknown dispersal capabilities of this life stage were studied in relation to logs, tree trunks, and adjacent leaf-litter areas in a mixed hardwood forest using mark-release-recapture methods. In two spatially and temporally well-spaced trials involving logs, the estimated mean distances that nymphs dispersed ranged from approximately 0.04 to 0.20 m/day on logs vs 0.11 to 0.72 m/day in litter. Prior to recapture in either trial and within the confines of the sampling grids, the greatest estimated dispersal distances by individual nymphs released on logs, and in litter 0.5 m or 1.5 m from logs, were 2.4, 3.0, and 3.0 m, respectively. Nymphs released on logs or litter tended to remain within the same biotopes in which they were freed while host-seeking. In two simultaneous trials involving trunks spaced close-at-hand, nymphs released at the trunk/litter interface on all four aspects collectively dispersed a mean of 0.353 m/day on trunks vs 0.175 m/day in litter. In either trial, the greatest distances that recaptured nymphs climbed trunks, or dispersed in litter in an encircling 3-m grid, were 1.55 m and 2.97 m, respectively. Nymphs ascending trunks did not exhibit a preference for any one aspect, and the B. burgdorferi-infection prevalences in nymphs that climbed trunks (3.2-4.0%) did not differ significantly from those that moved horizontally into litter (10.5-17.6%). We conclude that I. pacificus nymphs use an ambush host-seeking strategy; that they disperse slowly in all biotopes studied; that they usually continue to host-seek in or on whatever substratum they access initially; and that B. burgdorferi-infected nymphs are as likely to move horizontally as vertically when offered a choice.