A new cost‐effective and fast direct PCR protocol for insects based on PBS buffer

Insect DNA barcoding is a species identification technique used in biodiversity assessment and ecological studies. However, DNA extraction can result in the loss of up to 70% of DNA. Recent research has reported that direct PCR can overcome this issue. However, the success rates could still be improved, and tissues used for direct PCR could not be reused for further genetic studies. Here, we developed a direct PCR workflow that incorporates a 2‐min sample preparation in PBS‐buffer step for fast and effective universal insect species identification. The developed protocol achieved 100% success rates for amplification in six orders: Mantodea, Phasmatodea, Neuroptera, Odonata, Blattodea and Orthoptera. High and moderate success rates were obtained for five other species: Lepidoptera (97.3%), Coleoptera (93.8%), Diptera (90.5%), Hemiptera (81.8%) and Hymenoptera (75.0%). High‐quality sequencing data were also obtained from these amplifiable products, allowing confidence in species identification. The method was sensitive down to 1/4th of a 1‐mm fragment of leg or body and its success rates with oven‐dried, ethanol‐preserved, food, bat guano and museum specimens were 100%, 98.6%, 90.0%, 84.0% and 30.0%, respectively. In addition, the pre‐PCR solution (PBS with insect tissues) could be used for further DNA extraction if needed. The workflow will be beneficial in the fields of insect taxonomy and ecological studies due to its low cost, simplicity and applicability to highly degraded specimens.     

Ancient origin of high taxonomic richness among insects

Insects are a hyper-diverse group, comprising nearly three-quarters of all named animal species on the Earth, but the environmental drivers of their richness and the roles of ecological interactions and evolutionary innovations remain unclear. Previous studies have argued that family-level insect richness increased continuously over the evolutionary history of the group, but inclusion of extant family records artificially inflated the relative richness of younger time intervals. Here we apply sampling-standardization methods to a species-level database of fossil insect occurrences, removing biases present in previous richness curves. We show that insect family-richness peaked 125 Ma and that Recent values are only 1.5–3 times as high as the Late Palaeozoic. Rarefied species-richness data also tentatively suggest little or no net increase in richness over the past 125 Myr. The Cretaceous peak in family richness was coincident with major radiations within extant groups but occurred prior to extinctions within more basal groups. Those extinctions may in part be linked to mid-Cretaceous floral turnover following the evolution of flowering plants. Negligible net richness change over the past 125 Myr implies that major radiations within extant groups were offset by reduced richness within groups that are now relict or extinct.     

Efficiency of variable-intensity and sequential sampling for insect control decisions in cole crops in the Netherlands

A total of 24 commercial fields of cabbages and Brussels sprouts were sampled in a grid fashion with 20–25 equally spaced cells with four plants per cell. Using this data base of 80–100 plants, we conducted computer stimulations to compare the treatment decisions that would be made for the major insect pests using published sequential sampling programs and a newly developed variable-intensity sampling program. Additionally, we compared the number of samples required to make the decision. At low thresholds (10–20%) for both Lepidoptera and cabbage aphids, variable intensity-sampling required a smaller sample size and provided more reliable decisions, while at high thresholds (40–50%) sequential sampling provided more reliable decisions. In both procedures, the occurrence of incorrect decisions was minimal. The number of cases in which a decision would not be reached after a 40-plant sample was lower for variable-intensity sampling. Considering the number of samples required to make a correct decision and the greater need for reliable decisions at lower thresholds, variable-intensity sampling was superior to sequential sampling. Additionally, variable-intensity sampling has the advantage of requiring samples to be taken in a greater area of the field and thus increases the probability of detecting localized infestations. Although variable-intensity sampling was not designed to classify pest populations for treatment decisions but rather to achieve sampling precision around the population mean, our present studies indicate that it can also be an effective method to aid in treatment decisions.     

Cytoskeletal elements in arthropod sensilla and mammalian photoreceptors.

Ciliary receptor cells, typified by cilia or modified cilia, are very common in the animal kingdom. In addition to the cytoskeleton of their ciliary processes these receptors possess other specific prominent cytoskeletal elements. Two representative systems are presented: i) scolopidia, mechanosensitive sensilla of various arthropod species; and ii) photoreceptor cells of the retina of the bovine eye. Two cytoskeletal structures are characteristic for arthropod scolopidia: a scolopale typifies the innermost auxiliary cell, and long ciliary rootlets are extending well into the sensory cells. The latter element is also characteristic for the inner segment of the photoreceptor cells in bovine. The scolopale of scolopidia is mainly composed of actin filaments. In the absence of myosin, the uniform polarity of the actin filaments and their association with tropomyosin all indicate a stabilizing role of the filament bundles within the scolopale. This function and a certain elasticity of actin filament bundles may be important during stimulation of the sensilla. The ciliary rootlets of both systems originate at the basal bodies at the ciliary base of the sensory cells and project proximally. These rootlets are composed of longitudinally oriented, fine filaments forming a characteristic regular cross-striation. An alpha-actinin immunoreactivity was detected within the ciliary rootlets of scolopidia. In addition, antibodies to centrin react with the rootlets of both types of receptors. Since centrin is largely responsible for the contraction of the flagellar rootlets in green algae, contraction may also occur in the ciliary rootlets of insect sensilla and vertebrate photoreceptors. In both systems, contraction or relaxation of the ciliary rootlets could serve in sensory transduction or adaptation.     

晚侏罗世摇蚊科新属、种

本文描述了我国冀北和鲁东上侏罗统摇蚊科化石3属、3种,其中,1新属和3新种。冀北大北沟组中不存在Chironomaptera gregaria种化石,以前被鉴定为幽蚊科的这个种实际上应为摇蚊科的1个新种。并对如何区分上侏罗统这两个科成虫化石作了简述。     

Distribution of second generation European corn borer,Ostrinia nubilalis, egg masses in field corn and relationship to subsequent tunneling damage

The relationship between second generation European corn borer (Ostrinia nubilalis Hübner) egg mass numbers and subsequent field corn damage, as measured by stalk cavity numbers, was studied in 79 fields in northeastern North Carolina over three years. A mean of 0.028 egg masses per plant (645 egg masses/23400 plants) was found over the course of the study. Significant differences in oviposition rate were detected between fields and years. Ca. 85% of egg masses were deposited in a five leaf zone surrounding the primary ear; of these, 89% were found on the lower four leaves in this zone. Egg masses appeared to be distributed randomly within fields but at low rates of incidence, and oviposition was relatively uniform between sampling areas within individual fields. Under moderate to high oviposition pressure (mean number of egg masses per plant over the duration of the oviposition period >ca. 0.02), eggs laid during the early phases of the oviposition period account for more subsequent stalk damage than eggs laid during the later phases of the oviposition period. Variations in second generation egg mass numbers accounted for ca. 70% of variation in stalk cavity numbers.     

Structures related to pheromone storage in alar androconia and the female abdominal scent gland of Heliconius erato phyllis,Heliconius ethilla narcaea,and Heliconius besckei (Lepidoptera: Nymphalidae: Heliconiinae)

We describe the morphology of alar androconia and the female abdominal scent gland of Heliconius erato phyllis, Heliconius ethilla narcaea, and Heliconius besckei. Androconial scales of Heliconius, which are arranged in overlapping wing bands, release pheromones during courtship, probably through vibratory movements of male wings over the female to induce her to mate. An antiaphrodisiac is produced by glands located in the valves of the male and is transferred during copulation to the yellow dorsal abdominal sac present in the virgin female, causing this sac to emit a scent that reduces the attractiveness of the female for courtship with other males. Stereomicroscopy, SEM, and TEM analyses were conducted to describe the morphology of the internal and external scales and the external abdominal scent sac. The findings revealed different sizes of external androconial scales and an internal group of porous structural vesicles that are probably related to the preservation of internal space, reception and storage of secretions, and elimination of volatiles when the male is actively involved in courtship. Translucent projections on the female abdominal scent sac create open reservoirs for the reception, storage, and emission of antiaphrodisiac volatiles along with stink clubs. Male valve denticles vary in form and probably attach securely to the female sac during mating, thus ensuring secretion transfer. These features are discussed in the context of a comparative analysis.     

Host age and pathogen exposure level as factors in the susceptibility of the house fly,Musca domestica (Diptera: Muscidae) to Beauveria bassiana

Adult house flies, Musca domestica L., of four ages, <1, 3, 7, and 14 day post-eclosion, were exposed to three strains of Beauveria bassiana (P89, L90 and 447). Flies were exposed to moistened filter paper treated with either a low (1.57×10⁴ conidia/cm²) or high (1.57×10⁵ conidia/cm²) concentration of each fungal strain for 6 h. Strain 447 was superior to the two house fly-derived B. bassiana strains in inducing host infection and mortality. Significant spikes in infection and mortality occurred as early as 5 days post-exposure with higher concentration exposures acting more quickly. Few differences were observed in either infection or mortality among the four fly age classes. On Day 10 post-exposure, 77% of the high-concentration, 447-exposed flies were infected, compared with only 24% of the flies from the P89 low-concentration exposure. Potential applications of these results in integrated house fly management programs are discussed.     

Chitin production by arthropods in the hydrosphere

Chitin is widely distributed in nature and its annual production is thought to be huge. However, the chitin production has been rarely estimated in aquatic ecosystems, despite the growing economic interest in this polymer. Arthropods are one of the main chitin producers in the hydrosphere and a correct evaluation of the chitin production by these organisms in the different marine and freshwater ecosystems is of prime interest to understand their importance in the biogeochemical cycles of carbon and nitrogen. Such evaluation is also worth considering to achieve a rational exploitation of crustaceans which are currently the major source of chitin for the industry. Annual chitin production of crustaceans and insects in aquatic ecosystems was estimated on the basis of annual tissue production estimates and body chitin content measurements. About 800 annual tissue production estimates were collected from the literature. Estimates mainly concerned continental fresh waters and neritic ecosystems. Data were almost inexistent for athalassohaline and oceanic ecosystems. On the whole, 60% of the production estimates fell between 0.1 and 10.0 g dry weight m^–2 yr^–1. Published chitin levels in crustaceans and insects ranged from 3 to 16% of the whole body dry weight. Data were, however, lacking for some major groups such as trichopterans or amphipods. Aquatic insects and crustaceans were therefore collected and assayed for chitin using a highly specific enzymatic method. The chitin content of the collected insects (Coleoptera, Diptera, Ephemeroptera, Odonata, Plecoptera, Trichoptera) varied from 3 to 10% of the whole body dry weight; that of the collected crustaceans (Amphipoda, Branchiopoda, Copepoda) from 2.5 to 8.5% of the whole body dry weight. Total annual chitin production by arthropods had been estimated to 28 × 10⁶ T chitin yr^–1 for the freshwater ecosystems, to 6 × 10⁶ T chitin yr^–1 for athalassohaline ecosystems and to 1328 × 10⁶ T chitin yr^–1 for marine ecosystems. The importance of the chitin production corresponding to the formation of exuviae and peritrophic membranes in arthropods and the chitin production by non-arthropod organisms in the chitin budget of aquatic ecosystems was highlighted and discussed.