Animal communication systems are often exploited by eavesdropping antagonists, especially predators and ectoparasites. Female frog‐biting midges (Diptera: Corethrellidae) are known to use male anuran advertisement calls to locate their blood hosts, frogs. Here, we use acoustic midge traps broadcasting synthetic and recorded calls to identify those frog call parameters that affect midge attraction. At our study site in Pacific lowland Costa Rica, we found that overall midge attraction was influenced by both spectral and temporal acoustic parameters. Low dominant frequencies (below 1 kHz) and short pulse durations (between 125 and 500 ms) attracted the highest numbers of midges in tests with synthetic sinusoidal pure tones. These preferences partially explained the relative attractiveness of the advertisement calls of ten local frog species. The advertisement calls of the common and widespread Giant Bullfrog, Leptodactylus savagei (Anura: Leptodactylidae), attracted by far the largest number of midges, suggesting that this frog species might be a key resource for frog‐biting midges in Costa Rica. Although we found that calls of different frog species attracted different midge species/morphospecies in statistically different proportions, acoustic niche differentiation among midge species appeared to be moderate, suggesting either a limited degree of host specialization or the use of additional short‐range, that is, chemical, host recognition cues.

1. Female frog‐biting midges (Diptera: Corethrellidae) eavesdrop on the nocturnal mating calls of their blood hosts – male frogs. Available data suggest variable degrees of specialisation among Corethrella‐host associations, with limited information on the mechanisms involved in host selection and partitioning on a community level. 2. Our study provides a first comprehensive analysis of host interactions for a neotropical community of frog‐biting midges, based on both morphological and molecular genetic species delimitation. We used quantitative bipartite interaction networks to investigate host specificity among the midge‐frog community of La Gamba, Pacific lowland Costa Rica. 3. Midges that were collected directly from frog hosts (16 frog species) showed more pronounced levels of specificity (network‐wide degree of specialisation: H2′ = 0.3) than those caught with acoustic traps broadcasting their calls (12 frog species; H2′ = 0.08). This indicates that, despite a rather generalist acoustic foraging behaviour, frog‐biting midges discriminate between potential hosts by using additional close‐range recognition cues. 4. Based on COI and ITS2 sequencing data, we identified considerable levels of cryptic diversity within our five Corethrella morphotypes, with at least 17 distinct MOTUs of Corethrella in La Gamba. Including these MOTUs in bipartite network analyses produced higher resolution in species interactions, and increased estimators of network specificity (H2′ = 0.42).

Hematophagous arthropods often choose predictable feeding sites on their hosts´ body, presumably to maximize blood uptake while minimizing costs. Feeding sites can be host-specific, mediated by intrinsic host characters and/or specific preferences of the blood feeder. We investigated feeding site specificity in a community of frog-biting midges (Corethrella spp.) and frog hosts in La Gamba, Costa Rica. Midge distribution on hosts differed significantly between 12 investigated frog species, indicating that intrinsic host properties influence potential feeding sites. However, realized feeding sites were also significantly different between four investigated Corethrella morphotypes, across all hosts but also within certain shared hosts, indicating feeding site partitioning among Corethrella. We propose that the diversity of feeding sites in Corethrella-frog associations is determined by an interaction of host traits, e. g. calling site, defensive behavior or skin thickness, and midge traits, especially body size and corresponding mouthpart size/structure.

Hematophagous arthropods often choose predictable feeding sites on their hosts´ body, presumably to maximize blood uptake while minimizing costs. Realized feeding sites can be host specific, mediated by intrinsic host characters or/and specific preferences of the blood feeder. We investigated feeding site specificity in a community of frog-biting midges (Corethrella spp.) and frog hosts in La Gamba, Costa Rica. Midge distribution on hosts differed significantly between 12 investigated frog species, indicating that intrinsic host properties influence potential feeding sites. However, realized feeding sites were also significantly different between four investigated Corethrella morphotypes, across all hosts but also within certain shared hosts, indicating feeding site partitioning among Corethrella. We propose that the diversity of feeding sites in Corethrella-frog associations is determined by an interaction of host traits, e. g. calling site, defensive behavior or skin thickness, and midge traits, especially body size and corresponding mouthpart size/structure.

Females of frog-biting midges (Corethrellidae) obtain their blood meals from male calling frogs. While the morphology of the feeding apparatus is well studied in hematophagous Diptera that impact humans, frog-biting midges have received far less attention. We provide a detailed micromorphological examination of the piercing blood-sucking proboscis and maxillary palpus in three Corethrella species using scanning electron microscopy and histological semi-thin sectioning. We also compare the sensilla found on the proboscis tip and the palpus of Corethrella with other piercing blood-sucking Diptera. Corethrella spp. have a proboscis length of about 135 µm, equipped with delicate mandibular piercing structures composing the food canal together with the labrum and hypopharynx. Their proboscis composition is plesiomorphic and more similar to other short-proboscid hematophagous Culicomorpha (e.g., Simuliidae), in contrast to the phylogenetically more closely related long-proboscid Culicidae. As in other short-proboscid taxa, the salivary canal in Corethrella spp. transitions into an open salivary groove with one mandible forming a seal, whereas in Culicidae the salivary canal is closed until the tip of the proboscis. We discuss the possible functional constraints of very short, piercing blood-sucking proboscises (e.g., dimensions of host blood cells) that may limit the size of the food canal.