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In cold climates most aquatic habitats are frozen for many months. Nevertheless, even in such regions the conditions in different types of habitat, in different parts of one habitat, and from one year to the next can vary considerably; some water bodies even allow winter growth. Winter cold and ice provide challenges for aquatic insects, but so do high spring flows, short, cool summers, and unpredictable conditions. General adaptations to cope with these constraints, depending on species and habitat, include the use of widely available foods, increased food range, prolonged development (including development lasting more than one year per generation), programmed life cycles with diapause and other responses to environmental cues (often enforcing strict univoltinism), and staggered development. Winter conditions may be anticipated not only by diapause and related responses but also by movement for the winter to terrestrial habitats, to less severe aquatic habitats, or to different parts of the same habitat, and by construction of shelters. Winter itself is met by various types of cold hardiness, including tolerance of freezing in at least some species, especially chironomid midges, and supercooling even when surrounded by ice in others. Special cocoons provide protection in some species. A few species move during winter or resist anoxia beneath ice. Spring challenges of high flows and ice scour may be withstood or avoided by wintering in less severe habitats, penetrating the substrate, or delaying activity until after peak flow. However, where possible species emerge early in the spring to compensate for the shortness of the summer season, a trait enhanced (at least in some lentic habitats) by choosing overwintering sites that warm up first in spring. Relatively low summer temperatures are offset by development at low temperatures, by selection of warm habitats and microhabitats, and in adults by thermoregulation and modified mating activity. Notwithstanding the many abiotic constraints in cold climates, aquatic communities are relatively diverse, though dominated by taxa that combine traits such as cold adaptation with use of the habitats and foods that are most widely available and most favourable. Consequently, except in the most severe habitats, food chains and community structure are complex even at high latitudes and elevations, including many links between aquatic and terrestrial habitats. Despite the complex involvement of aquatic insects in these cold-climate ecosystems, we know relatively little about the physiological and biochemical basis of their cold hardiness and its relationship to habitat conditions, especially compared with information about terrestrial species from the same regions.
Systematics and morphology / Systématique et morphologie
This study deals with two species of the genus Phtheiropoios, redescribing P. tucumanusCicchino, 1990, previously known from five specimens collected on Ctenomys tucumanus Thomas, 1900, and describing P. inaequalissp. nov. from C. tuconax Thomas, 1925, both from different localities in Tucumán Province, Argentina. Diagnostic features for the new species include proportion of the male forficula, male external genitalia, and counts of setae and body measurements in both sexes. Brief comments on the morphological affinities of these species with other species of Phtheiropoios, and a key to males of all species of the genus Phtheiropoios known to parasitize rodents of the genus Ctenomys, are included.
The millipede Perunosoma trojanicagen. nov., sp. nov. is described on the basis of specimens from the Prekonoška Pećina Cave in southeast Serbia. Scanning electron micrographs of the gonopods and legs are presented. Comparative photomicrographs of the closely related genus SerbosomaĆurčić and Makarov, 2000 are also presented. The central part of the anterior gonopods in these genera can be species-specific and provide grounds for initial recognition of species. The Anthroleucosomatidae occupy three disjunct areas globally: one on the west coast of North America, the second in Asia, and the third in Europe. The North American anthroleucosomatid fauna is composed of one monotypic genus, while the Asian one includes six genera with seven species and the much more diverse European anthroleucosomatids include 14 genera with 39 species.
The larvae of the four species of primary flea parasites of the mountain beaver, Aplodontia rufa (Rafinesque), are described and illustrated for the first time, and a key to their identification is provided. The larva of Hystrichopsylla schefferi Chapin is very large, with a total body length of more than 10 mm in the late third instar. Its mandible, with a series of marginal teeth along a scoop-shaped tip, is characteristic of members of the formerly recognized subgenus Hystroceras. The larvae of Paratyphloceras oregonensis Ewing and Trichopsylloides oregonensis Ewing are very similar to one another, but the former is much larger, with a total body length of about 8 mm in the late third instar, compared with 5 mm for the latter. These two species can also be separated in all instars on the basis of the setation on the abdominal segments. The larva of Dolichopsyllus stylosus (Baker) is extraordinary. The mandible bears two enormous, tusklike setae on a swollen base, the hypopharynx is a spiny, trilobed structure without setae, and there are five processes on the labial palps instead of the four typical in other species.
The acute toxicities of an extract obtained from a plant within the Piperaceae family and related synthetic analogues were tested against four common Canadian forest pest insects. The acute toxicity of the extract from black pepper, Piper nigrum L., was assessed after 1, 24, and 72 h by the percent larval mortality. The 24 h LC50 estimates for the P. nigrum extract were (in order of decreasing sensitivity) 0.012% for the introduced pine sawfly, Diprion similis (Hartig) (Hymenoptera: Diprionidae), 0.053% for the forest tent caterpillar, Malacosoma disstria Hubner (Lepidoptera: Lasiocampidae), 0.282% for the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), and 0.998% for the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Torticidae). There was no significant increase in mortality after 72 h. Seventy percent of L. dispar larvae dropped off or moved from branches within 1 h of application of 0.2% P. nigrum extract, indicating that these compounds have a repellent effect. Pipercide and nor-pipercide were more toxic to L. dispar and M. disstria larvae than piperolein A and a P. sarmentosum Roxb. amide 72 h after either oral or topical administration of these compounds. Toxic effects of piperamides were more pronounced by oral ingestion. Ninety percent mortality of L. dispar larvae occurred following an oral dose of 5 μg pipercide in diet, whereas mortality was only 40% following topical treatment at 5 μg pipercide/insect. Whole Piper extracts might be useful for the control of sawflies and tent caterpillars in small-scale applications, based on the demonstrated efficacy and reduced risk potential.
High levels of azinphos-methyl (0.4–0.8 μg/L) were detected in the Wilmot River, Prince Edward Island, Canada, following runoff from an agricultural field after a heavy rainfall on 19 July 2002. Benthic macroinvertebrate abundance and diversity were sharply lower in samples collected 1 d after the event compared with samples collected in the same manner in July or October 2001. The greatest effects were noticed on the aquatic insects, whose abundance declined from >10 000 individuals per 3-min kick sample in July 2001 to <900 individuals per 3-min kick sample in July 2002. One family of Diptera, one family of Plecoptera, and three families of Trichoptera disappeared entirely from the study reach after the runoff event, and several other families were severely depleted in number. This led to low taxonomic similarity values between the communities before and after the runoff event and a change relative to reference streams on PEI. Examination of biological metrics (including indices such as % EPT (Ephemeroptera, Plecoptera, or Trichoptera), % chironomids, % burrowers, etc.) confirmed that aquatic insects were more heavily targeted by the insecticide than non-insect invertebrates. This resulted in a shift in the community towards non-insect taxa that were better able to avoid or tolerate this type of pollution.
Laboratory experiments were conducted to evaluate the contact and oral toxicity of commercial formulations of spinosad and deltamethrin to adults of the crucifer flea beetle, Phyllotreta cruciferae (Goeze). Method of exposure had a significant effect on flea beetle mortality and feeding damage to canola seedlings. Topical treatment of flea beetles with deltamethrin or different concentrations of spinosad resulted in significantly lower mortality and higher feeding damage than exposure to treated canola cotyledons. Results indicated that spinosad was more toxic by ingestion than by topical contact. Mortality from treated cotyledons was significantly higher with 60 ppm deltamethrin than with 80 or 120 ppm spinosad after 24 h exposure but not after 120 h exposure. Delayed mortality in the spinosad treatments did not result in high feeding damage; damage after 120 h was not significantly different in the spinosad and deltamethrin treatments. Low concentrations of spinosad (40 ppm) strongly inhibited feeding activity within 24 h after exposure. Mortality from spinosad was higher after beetles were exposed to treated cotyledons for 120 h than for 24 h. Mortality from spinosad, but not deltamethrin, was significantly higher at 25 °C than at 15 °C. An ionic surfactant, polyethylenimine, increased the toxicity of 40 ppm spinosad. Our study suggests that spinosad has potential for use as an insecticide against crucifer flea beetles on canola.
Mitochondrial cytochrome oxidase I and II genes were sequenced for two invasive alien birch (Betula L. [Betulaceae]) leaf-mining sawflies, Profenusa thomsoni (Konow, 1886) (Hymenoptera: Tenthredinidae) and Scolioneura betuleti (Klug, 1816) (Hymenoptera: Tenthredinidae), accidentally introduced from Europe to North America. Ten North American and two European populations of P. thomsoni were sampled. As no genetic variation was observed for this parthenogenic species in Europe or North America, there is no evidence that this species was introduced more than once into North America. A single Canadian population of putative S. betuleti was genetically characterized and compared with populations of S. betuleti and Scolioneura vicina Konow, 1894 in Europe to resolve the species identity of the introduced Canadian population. Three haplotypes were present in European material but only one haplotype was represented in material collected in Canada. The haplotype in the Canadian population occurred in both S. betuleti and S. vicina in Europe. Thus, this preliminary genetic work cannot provide certain identity of the Canadian species. Moreover, there was no significant genetic difference between putative S. betuleti and S. vicina in Europe, leading us to suggest that S. vicina may not be reproductively isolated from S. betuleti, despite ecological differences.
Each fall, honey bee (Apis mellifera L. (Hymenoptera: Apidae)) colonies in northern temperate regions rear a population of long-lived winter bees that maintains a broodless nest throughout the winter and resumes brood-rearing activities in the spring. Pollen supply in colonies is closely tied to this phenomenon; winter bees sequester large reservoirs of pollen-derived nutrients in their bodies and the brood-rearing capacity of colonies is dictated by the availability of pollen. We determined the effects of manipulating pollen supply during the fall on the number of winter bees present in colonies by spring, their mass and protein content before and after winter, and their capacity to rear brood during the spring. Colonies were either supplemented with or partially deprived of pollen during the fall, while a third group of colonies was not manipulated (control). We found that the performance of winter bees was not enhanced by supplementing colonies with pollen in the fall, nor did worker function suffer if pollen supply was restricted. Similar numbers of winter bees survived to spring in colonies and workers had similar physiology and brood-rearing efficiencies. These results suggest that beekeepers would not benefit by investing in fall pollen supplements to maximize colony growth in early spring.
A dual-choice behavioral bioassay and gas chromatography – electroantennogram detection (GC–EAD) were used to determine the effect of host terpenes and nonhost green-leaf volatiles (GLVs) on the oviposition preference of the spruce budworm, Choristoneura fumiferana (Clemens). Some emphasis was placed on assessing the ability of females to distinguish between enantiomers of chiral monoterpenes because ( )-α-pinene but not (−)-α-pinene or (±)-α-pinene had been shown previously to promote oviposition. Headspace volatiles from white spruce, Picea glauca (Moench) Voss (Pinaceae), and balsam fir, Abies balsamea (L.) Mill. (Pinaceae), were sampled using solid-phase microextraction and identified by gas chromatography – mass spectrometry with the aid of a chiral column. Females deposited significantly more egg masses on filter paper substrate treated with host monoterpenes than on controls. Contrary to expectation, substrates treated with several GLVs were also preferred over the controls. None of the GLVs or terpenes was deterrent. Females showed no significant ability in either the behavioral or the GC–EAD bioassays to distinguish between enantiomers of selected chiral monoterpenes, including α-pinene, in contrast to earlier findings. We conclude that host terpenes serve as general rather than host-specific oviposition stimuli for spruce budworm.
Laricobius nigrinus Fender is being reared for release as a biological control agent for hemlock woolly adelgid (HWA), Adelges tsugae Annand. HWA is an introduced insect lethal to hemlock trees (Tsuga canadensis (L.) Carr. and T. caroliniana Engelm.) in the eastern United States. In nature, the predator (Laricobius nigrinus) and its prey (HWA) undergo a dormant period in the summer (aestivation). In the laboratory, the aestivation of L. nigrinus has not been synchronized with that of HWA, resulting in significant predator mortality. Four factors (genetics, temperature, photoperiod, and moisture) were investigated for their effects on aestivation in L. nigrinus. Both the number of individuals and the time at which they emerged from aestivation were measured in response to these factors. Temperature was the most important cue for termination of aestivation, and photoperiod was a modifying factor. High temperature and long day length delayed emergence and high moisture levels resulted in greater emergence but did not affect emergence time. Genetics, as represented by broods, was not a major factor in aestivation termination. These results have led to improvement in rearing L. nigrinus, since emergence from aestivation can now be synchronized with the active period of HWA. Increased success in rearing has expedited field releases of L. nigrinus in the eastern United States.
Biodiversity and evolution / Biodiversité et évolution
New records of the ptyctimous mites from the Nearctic Region are given. The new material includes 27 species of ptyctimous mites. The geographical distributions of seven species are more extensive than previously known.