Vertical Stratification of Insect Species Developing in Water-Filled Tree Holes

Forest ecosystems have a distinct vertical dimension, but the structuring of communities in this three-dimensional space is not well understood. Water-filled tree holes are natural microcosms structured in metacommunities. Here, we used these microcosms as model systems to analyze how insect communities and the occurrence and abundance of individual species are influenced by biotic and abiotic microhabitat characteristics, the vertical position of the tree hole, and stand-scale habitat availability. We found that both the characteristics of water-filled tree holes and their insect communities differ significantly between canopy and ground level. Individual insect species showed contrasting responses to the vertical position of the tree holes when important environmental factors at the stand and the tree-hole scale were considered. While some species, such as the mosquito Aedes geniculatus and the beetle Prionocyphon serricornis, decreased in abundance with increasing tree-hole height, the biting midge Dasyhelea sp., the non-biting midge Metriocnemus cavicola and the hoverfly Myiatropa florea increased in abundance. Our results suggest that vertical stratification in forests is most likely driven not only by variation in tree-hole microhabitat properties, i.e., niche separation, but also by individual species traits, such as adult dispersal propensity, food preferences and mating behavior of adult stages, and interspecific competition of larval stages. Therefore, communities of insect species developing in tree holes are likely structured by competition–colonization trade-offs predicted by metacommunity theory.

First Report of Culicoides Biting Midges (Diptera: Ceratopogonidae) Attacking People in Italy, With the Description of Extreme Larval Breeding Sites and Diurnal Activity of Culicoides riethi

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) play a paramount role in medical and veterinary entomology worldwide, particularly as vectors of pathogens which cause animal diseases. Biting midges are also infamous for the nuisance they provoke to people involved in outdoor activities. Nonetheless, attacks to man by midges from any Culicoides species have not been reported in Italy. An entomological investigation was performed following repeated attacks to man in a nature park near Rome (central Italy). The study area is a natural degassing zone, characterized by widespread hazardous gas emissions of CO2 and H2S, with several water bodies including permanent lakes, ponds, and pools. The biting midge C. riethi Kieffer, 1914 was very active during daytime in the period April–June. The species has been identified as responsible for attacks on people in the area. An in-depth analysis of the extreme environmental conditions revealed the ability of larvae to thrive in several water bodies, characterized by an extremely low pH and a high concentration of sulfates.

Culicoides Latreille (Diptera: Ceratopogonidae) as potential vectors for Leishmania martiniquensis and Trypanosoma sp. in northern Thailand

Biting midges of genus Culicoides (Diptera: Ceratopogonidae) are the vectors of several pathogenic arboviruses and parasites of humans and animals. Several reports have suggested that biting midges might be a potential vector of Leishmania parasites. In this study, we screened for Leishmania and Trypanosoma DNA in biting midges collected from near the home of a leishmaniasis patient in Lamphun province, northern Thailand by using UV-CDC light traps. The identification of biting midge species was based on morphological characters and confirmed using the Cytochrome C oxidase subunit I (COI) gene. The detection of Leishmania and Trypanosoma DNA was performed by amplifying the internal transcribed spacer 1 (ITS1) and small subunit ribosomal RNA (SSU rRNA) genes, respectively. All the amplified PCR amplicons were cloned and sequenced. The collected 223 biting midges belonged to seven species (Culicoides mahasarakhamense, C. guttifer, C. innoxius, C. sumatrae, C. huffi, C. oxystoma, and C. palpifer). The dominant species found in this study was C. mahasarakhamense (47.53%). Leishmania martiniquensis DNA was detected in three samples of 106 specimens of C. mahasarakhamense tested indicating a field infection rate of 2.83%, which is comparable to reported rates in local phlebotomines. Moreover, we also detected Trypanosoma sp. DNA in one sample of C. huffi. To our knowledge, this is the first molecular detection of L. martiniquensis in C. mahasarakhamense as well as the first detection of avian Trypanosoma in C. huffi. Blood meal analysis of engorged specimens of C. mahasarakhamense, C. guttifer, and C. huffi revealed that all specimens had fed on avian, however, further studies of the host ranges of Culicoides are needed to gain a better insight of potential vectors of emerging leishmaniasis. Clarification of the vectors of these parasites is also important to provide tools to establish effective disease prevention and control programs in Thailand.

Occurrence of Biting Midges (Diptera: Culicoides) on Dairy Farms in Eastern Slovakia in Relation to Abiotic Factors

Within the scope of our research, we have performed 59 trapping sessions and collected 15,756 biting midges from 20 species at four farms (Kluknava, Ostrov, Turňa nad Bodovou and Zemplínska Teplica), The most frequent types of captured insects were representatives of the Avaritia subgenus, C. obsoletus/C. scoticus, representing on average 85.1 % (13,295 individuals) of the fauna of the biting midges, with the exception of the farm in Ostrov where this group represented only 41.7 % of the fauna. At this particular farm, the most frequently trapped insects belonged to the Culicoides subgenus (54.1 %), in particular the C. bysta, C. lupicaris, C. newsteadi, C. Pulicaris and C. Punctatus species. During the trapping sessions, we monitored factors affecting the number of trapped biting midges, such as the temperature, relative air humidity and airflow rate: the air temperature during the trapping of the biting midges ranged from 9.8 to 26.2 °C; the relative air humidity ranged from 35.1 to 100 %; and the air flow rate ranged from no wind to a wind velocity of 8.2 m.s-1. However, in the final evaluation, we failed to observe a statistically significant correlation between the air flow and the number of trapped biting midges. The largest amounts of biting midges were trapped at temperatures ranging from 15.8 to 24.6 °C and at a relative air humidity ranging from 54.2 % to 68.6 %. While monitoring the seasonal dynamics of the physiological conditions of biting midge females at the selected farms, we confirmed that during the period from June to August, the most frequently trapped females were parous (50.1 %; 7,826 individuals). In addition, nulliparous females comprised 43.8 % (6,842 individuals) and were continuously trapped throughout the season (April— November).

Transcriptome profiling reveals the developmental regulation of NaCl-treated Forcipomyia taiwana eggs

Background The biting midge, Forcipomyia taiwana, is one of the most annoying blood-sucking pests in Taiwan. Current chemical control methods only target the adult, not the immature stages (egg to pupa), of F. taiwana. Discovering new or alternative tactics to enhance or replace existing methods are urgently needed to improve the effectiveness of F. taiwana control. The egg is the least understood life stage in this pest species but may offer a novel point of control as addition of NaCl to the egg environment inhibits development. Thus, the objective of this study was to use RNA profiling to better understand the developmental differences between wild-type melanized (black) and NaCl-induced un-melanized (pink), infertile F. taiwana eggs. Results After de novo assembly with Trinity, 87,415 non-redundant transcripts (Ft-nr) with an N50 of 1099 were obtained. Of these, 26,247 (30%) transcripts were predicted to have long open reading frames (ORFs, defined here as ≥300 nt) and 15,270 (17.5%) transcripts have at least one predicted functional domain. A comparison between two biological replicates each of black and pink egg samples, although limited in sample size, revealed 5898 differentially expressed genes (DEGs; 40.9% of the transcripts with long ORFs) with ≥2-fold difference. Of these, 2030 were annotated to a Gene Ontology biological process and along with gene expression patterns can be separated into 5 clusters. KEGG pathway analysis revealed that 1589 transcripts could be assigned to 18 significantly enriched pathways in 2 main categories (metabolism and environmental information processing). As expected, most (88.32%) of these DEGs were down-regulated in the pink eggs. Surprisingly, the majority of genes associated with the pigmentation GO term were up-regulated in the pink egg samples. However, the two key terminal genes of the melanin synthesis pathway, laccase2 and DCE/yellow, were significantly down-regulated, and further verified by qRT-PCR. Conclusion We have assembled and annotated the first egg transcriptome for F. taiwana, a biting midge. Our results suggest that down-regulation of the laccase2 and DCE/yellow genes might be the mechanism responsible for the NaCl-induced inhibition of melanization of F. taiwana eggs.