B. A. Foote

MIDGE LARVAE (DIPTERA: CHIRONOMIDAE) AS INDICATORS OF POSTMORTEM SUBMERSION INTERVAL OF CARCASSES IN A WOODLAND STREAM : A PRELIMINARY REPORT

Data on colonization of rat carcasses by aquatic insects in riffle and pool areas of a small woodland stream were obtained to elucidate patterns potentially useful for determining the postmortem submersion interval of corpses in flowing water habitats. After 39 days, the carcasses had no visual signs of deterioration in the absence of large scavenging animals. Midge larvae (Diptera: Chironomidae) were the dominant insects colonizing the carcasses. No patterns in numbers of larvae over time were evident, but the diversity of genera increased after 29 days in the riffle. Also, Orthocladius larvae did not begin to colonize the carcasses until after 13 days of submersion in the riffle and after 20 days of submersion in the pool. Although separated only by 20 m, the riffle and pool rats had dissimilar faunal assemblages. This suggests that different indices for determining the postmortem submersion interval of corpses based on midge larvae colonization should be developed for these two habitats. This investigation does not provide replicated data, but does shed light on what may happen to mammalian carcasses placed in a stream at a particular time of the year.

Parallel evolution of larval morphology and habitat in the snail-killing fly genus Tetanocera.

In this study, we sequenced one nuclear and three mitochondrial DNA loci to construct a robust estimate of phylogeny for all available species of Tetanocera. Character optimizations suggested that aquatic habitat was the ancestral condition for Tetanocera larvae, and that there were at least three parallel transitions to terrestrial habitat, with one reversal. Maximum likelihood analyses of character state transformations showed significant correlations between habitat transitions and changes in four larval morphological characteristics (cuticular pigmentation and three characters associated with the posterior spiracular disc). We provide evidence that phylogenetic niche conservatism has been responsible for the maintenance of aquatic‐associated larval morphological character states, and that concerted convergence and/or gene linkage was responsible for parallel morphological changes that were derived in conjunction with habitat transitions. These habitat–morphology associations were consistent with the action of natural selection in facilitating the morphological changes that occurred during parallel aquatic to terrestrial habitat transitions in Tetanocera.

Key Aspects of the Biology of Snail-Killing Sciomyzidae Flies

The biology of snail-killing flies (Diptera: Sciomyzidae) has been studied intensively over the past half-century, especially over the past decade. Today, sciomyzids are biologically the best-known group of higher Diptera. The overarching research objectives are evaluation of sciomyzids as biocontrols of disease-carrying or agriculturally important snails and slugs and as a paradigm group for the study of the evolution of diverse feeding and associated behaviors in flies. We present reviews and analyses of some key features of particular scientific and societal interest, including behavioral and phenological groups; laboratory experimental studies on behavior and development; population biology, bioindicators, ecosystem service provision, and conservation; phylogenetics, molecular studies, and evolutionary biology; and biocontrol.

Biology and Larval Feeding Habits of Coexisting Hydroptilidae (Trichoptera) from a Small Woodland Stream in Northeastern Ohio

Abstract Hydroptila consimilis Mosely, Ochrotrichia spinosa (Ross), and O. wojcickyi Blickle exhibited a close association with the appearance of the filamentous chlorophyte Cladophora (April to June) in a small woodland stream in northeastern Ohio. Laboratory rearings showed that these microcaddisflies displayed similar life cycles and exhibited hypermetamorphosis. H. consimilis mandibles are specialized for piercing individual cells within filaments of Cladophora to facilitate removal of cellular contents, whereas Ochrotrichia spp. have robustly cusped mandibles suited for piercing Cladophora and scraping diatoms from benthic substrates. Proportional similarity analysis of videotaped behavior illustrated that the feeding habits of third-instar Ochrotrichia exhibited a low similarity (0.44) to the other instars tested (Ochrotrichia fifth and Hydroptila first, third, and fifth) because of their frequent consumption of diatoms (17% of feeding efforts); all other instars tested were highly similar to each other (0.72–0.86). This division of trophic resources (i.e., differential use of diatoms versus Cladophora) minimized niche overlap between the two genera. All instars of H. consimilis and Ochrotrichia spp. fed heavily on the apical (therefore the smallest) cells of Cladophora filaments, and the time required to consume cells decreased significantly as larvae matured (P < 0.05). Larval Hydroptilidae are well adapted morphologically and behaviorally to consume Cladophora, and these algal filaments appear to represent a heterogeneous food source just as terrestrial host plants are for the array of phytophagous insects that use them.

Widespread and persistent invasions of terrestrial habitats coincident with larval feeding behavior transitions during snail-killing fly evolution (Diptera: Sciomyzidae).

BackgroundTransitions in habitats and feeding behaviors were fundamental to the diversification of life on Earth. There is ongoing debate regarding the typical directionality of transitions between aquatic and terrestrial habitats and the mechanisms responsible for the preponderance of terrestrial to aquatic transitions. Snail-killing flies (Diptera: Sciomyzidae) represent an excellent model system to study such transitions because their larvae display a range of feeding behaviors, being predators, parasitoids or saprophages of a variety of mollusks in freshwater, shoreline and dry terrestrial habitats. The remarkable genus Tetanocera (Tetanocerini) occupies five larval feeding groups and all of the habitat types mentioned above. This study has four principal objectives: (i) construct a robust estimate of phylogeny for Tetanocera and Tetanocerini, (ii) estimate the evolutionary transitions in larval feeding behaviors and habitats, (iii) test the monophyly of feeding groups and (iv) identify mechanisms underlying sciomyzid habitat and feeding behavior evolution.ResultsBayesian inference and maximum likelihood analyses of molecular data provided strong support that the Sciomyzini, Tetanocerini and Tetanocera are monophyletic. However, the monophyly of many behavioral groupings was rejected via phylogenetic constraint analyses. We determined that (i) the ancestral sciomyzid lineage was terrestrial, (ii) there was a single terrestrial to aquatic habitat transition early in the evolution of the Tetanocerini and (iii) there were at least 10 independent aquatic to terrestrial habitat transitions and at least 15 feeding behavior transitions during tetanocerine phylogenesis. The ancestor of Tetanocera was aquatic with five lineages making independent transitions to terrestrial habitats and seven making independent transitions in feeding behaviors.ConclusionsThe preponderance of aquatic to terrestrial transitions in sciomyzids goes against the trend generally observed across eukaryotes. Damp shoreline habitats are likely transitional where larvae can change habitat but still have similar prey available. Transitioning from aquatic to terrestrial habitats is likely easier than the reverse for sciomyzids because morphological characters associated with air-breathing while under the waters surface are lost rather than gained, and sciomyzids originated and diversified during a general drying period in Earths history. Our results imply that any animal lineage having aquatic and terrestrial members, respiring the same way in both habitats and having the same type of food available in both habitats could show a similar pattern of multiple independent habitat transitions coincident with changes in behavioral and morphological traits.

Biology and Immature Stages Of Snail-Killing Flies Belonging To the Genus Tetanocera (Diptera: Sciomyzidae). IV. Life Histories Of Predators Of Land Snails and Slugs

Abstract The biology and immature stages of snail-killing flies (Diptera: Sciomzyidae) that are predators on land snails and slugs are presented, including the geographic distribution, habitat occurrence, life cycle, and larval feeding habits of three species of Tetanocera Duméril preying on slugs (Tetanocera clara Loew, Tetanocera plebeja Loew, and Tetanocera valida Loew), and one species attacking land snails (Tetanocera phyllophora Melander).

Biology and Immature Stages of Snail-Killing Flies Belonging to the Genus Tetanocera (Diptera: Sciomyzidae). V. Biology of Three Additional Species Having Larvae that Prey on Aquatic Pulmonate Snails

ABSTRACT Information is presented on the distribution, life histories, and larval feeding habits of three species of Tetanocera Duméril (T. bergi Steyskal, T. plumosa Loew, T. stricklandi Steyskal) that prey as larvae on pulmonate aquatic snails. Tetanocera bergi is widely distributed in the western United States and Canadian provinces, T. stricklandi is known only from Alberta, and T. plumosa has a transcontinental distribution. Larvae of all three species are general feeders and consume several taxa of aquatic snails.

Pherbellia anitae, a New Species of Snail-Killing Fly (Diptera: Sciomyzidae) from Arizona

Abstract. Pherbellia anitae Foote, sp. nov., from southeastern Arizona, is described, and the male postabdomen is illustrated.

Biology and Immature Stages of Snail-Killing Flies Belonging to the Genus Tetanocera (Insecta: Diptera: Sciomyzidae). VI. Descriptions of Immature Stages and Keys to the Larvae and Puparia of the Nearctic Species

ABSTRACT The eggs, third-instar larvae, and puparia of 18 species of Nearctic Tetanocera are described and illustrated. Species keys to third-instar larvae and puparia are presented.