Xenochironomus canterburyensis (Diptera: Chironomidae) an insectan inquiline commensal of Hyridella menziesi (Mollusca: Lamellibranchia)

Larvae and pupae of the chironomid Xenochironomus canterburyensis (Freeman) are recorded for the first time. They are inquiline commensals of the fresh water mussel Hyridella menziesi (Gray) in Lake Taupo, New Zealand. The chironomid is univoltine and closely dependent on the seasonal growth of the mussel shell for its pupation and adult emergence. The first instar larva is probably a free-swimming, dispersal stage. Second instar larvae appeared in mussels between the outer surface of the mantle and the inner surface of the valve in later summer. They overwintered there as third and fourth instars until spring when they were found at the margin of the valve opposite the inhalent siphon from where they pupated and left the host to emerge at the lake surface. Some mortality of first and second instar larvae occurred as there was an average of 25–5 whole larvae buried in the nacre of each valve of the mussels.     

Xenochironomus canterburyensis (Diptera: Chironomidae), a commensal of Hyridella menziesi (Lamellibranchia) in Lake Taupo; features of pre-adult life history

Abstract

The larvae and pupae of the univoltine chironomid Xenochironomus canterburyensis (Freeman) are inquiline commensals of the freshwater mussel Hyridella menziesi (Gray). The 1st- and 2nd-instar larvae enter the mantle/valve cavity of the mussel in midsummer, and by early winter migrate as 3rd-instar larvae to the posterior end of the valve to lodge near its margin beside the inhalant siphon. During the spring, growth of the periostracum of the valve margin between the larva and the mantle of the mussel leaves the 4th-instar larva outside the mantle/valve cavity, where it pupates before leaving the mussel for the lake surface and adult emergence.     

Incidence of deformed chironomid larvae (Diptera: Chironomidae) in Swedish lakes

The occurrence of deformed mouth parts in recent and subfossil material of mostly Chironomus, Micropsectra and Tanytarsus increased from less than 1 % of the larvae at unpolluted sites or time periods to figures in the range of approx. 5–25% at strongly polluted sites. Deformities occurred in species that are widely separate in taxonomic position and way of living. Several heavy metals are suspected causative agents. Deformities in various mouth parts are illustrated by SEM photographs.     

Grazing rate determination of Corynoneura scutellata Winnertz (Chironomidae: Diptera)

Corynoneura scutellata Winnertz (Chironomidae: Diptera) grazing rates were determined radiometrically at different temperatures. The resulting temperature-grazing function was used to calculate C. scutellata grazing rates in the littoral zone of a Rhode Island lake. These grazing rates were compared to periphyton net accumulation rates, grazing rate: accumulation rate ratios ranged from 3–15% with a maximum of 70%.     

Phenology and life history of Belgica antarctica, an Antarctic midge (Diptera: Chironomidae)

ABSTRACT.

• 1 An account of the life-history with emphasis on phenology and number of instars is presented for Belgica antarctica Jacobs, the southernmost holometabolous insect.
• 2 Contrary to earlier reports, Belgica has four instars, in common with most other chironomids. Mean head capsule lengths varied between different populations but no overlap was found between discrete size classes of successive instars.
• 3 Belgica overwinters in all four instars.
• 4 Relative frequency of different instars from samples taken through the season indicates that a 2-year life-span is the commonest pattern.
• 5 Emergence of adults is relatively synchronous. Belgica exhibits protandry, which may be established at the time of pupation.

     

Revision of the kelp family Alariaceae and the taxonomic affinities of Lessoniopsis Reinke (Laminariales,Phaeophyta)

The morphologically diverse members of the Laminariales are separated into three families, the Alariaceae, Laminariaceae and Lessoniaceae, on the basis of developmental features exhibited at the stipeblade transition zone. We have investigated the relationships of lessoniacean taxa with those of alariacean and laminariacean affinity. This was done by completing phylogenetic analyses of 3 small-subunit (SSU) rRNA gene (113 bp), first internal transcribed spacer (ITS 1), 5.8S rRNA gene and second internal transcribed spacer (ITS2)(12 bp) sequence data from a variety of taxa. In summary, the Alariaceae and Lessoniaceae are polyphyletic. We present a restricted view of the Alariaceae, including only Alaria and Pterygophora of the genera usually placed in this family, and transfer the monotypic genus Lessoniopsis to this group. Current theories of kelp evolution and biogeography must be reconsidered in view of our data.     

Life cycle and production of Chironomidae (Diptera) from Lake Banyoles (NE Spain)

1. The life cycles and annual production of the eight most abundant species of chironomids (Prodadius cf. choreus, Tanypus punctipennis, Chironomus bernensis, Chironomus gr. plumosus, Cladopelma virescens, Microchironomus tencr, Tanytarsus gr. lestagei, and Cladotanytarsus atridorsum) were studied from sublittoral and profundal samples taken monthly in Lake Banyoles during 1987 at five sampling stations (depths ranging from 5 to 20 m). 2. The number of generations per year deduced from instar-frequency data varied from one to four, depending on the species, lake basin and depth. Annual temperature range, dissolved oxygen in the stratified period and presence of sulphide are the key factors that may explain the differences in the number of generations. 3. Production estimates were calculated using the size-frequency (SF) method corrected for the number of generations (SFG), and the increment-summation method (IS) when cohorts could be clearly deduced. 4. Production calculated with the SFG method gave results which were comparable with those of the IS method using smoothed-survivorship curves in the three species for which the use of the IS method was possible (C. virescens, M. tener and C. atridorsum). Using these methods production was estimated to range from 23–70 mg AFDW (ash-free dry weight) m^?2 yr^?1 at 12 m to 74–275 mg AFDW m^?2 yr^?1 in the sublittoral zone of the lake (5-m depth). 5. Calculation of production for the other five species using the size-frequency method with the number of generations (SFG) deduced from monthly instar-frequency data gave values ranging from 12 mg AFDW m^?2 yr^?1 (Chironomus bernensis at 20 m depth) to 3.75 g AFDW m^?2 yr^?1(Prodadius cf. choreus at 12 m). 6. Total chironomid production (with the SFG method) varied from 0.8 to 5 g AFDW m^?2 yr^?1 in the profundal and sublittoral, respectively. At each sampling station two species groups accounted for most of the production: Prodadius cf. choreus and Chironomus spp. Annual production/biomass ratio (P/B) varied from very high values for Prodadius (between 11 and 27, as four generations completed each year) to very low values for Chironomus gr. plumosus (2.20), which completed only one generation each year. The annual production of P. cf. choreus in Lake Banyoles is higher than any reported in the literature due to the completion of four generations and to the high densities of this species.     

Life history stages and taxonomy of Austrosimulium (Austrosimulium) tillyardianum (Diptera: Simuliidae)

The male, female, pupa, 9th‐instar larva, and egg of Austrosimulium (Austrosimulium) tillyardianum Dumbleton, 1973, are redescribed, and larval instars one to eight are described and morphologically differentiated for the first time. The relationship of A. (A.) tillyardianum to other New Zealand species is briefly reviewed.     

Some immature stages of the subgenus Chironomus (Meigen) (Diptera:Chironomidae) from Malawi,Central Africa

An account is given of the diagnostic characters of the larvae and pupae of 10 of the 18 African species of the subgenus Chironomus Meigen from a wide range of habitats in southern Malawi.     

Food preferences of tanypodinae larvae (Diptera: Chironomidae)

Analyses of the gut contents of larvae of three species of Tanypodinae, collected from four sites in north-east England and Scotland, invariably showed small particles (1–10 µm²), predominantly of detritus, to be more abundant than large particles (10–100 µm²), mostly algae and diatoms. No animal remains, such as carapaces, head capsules and chaetae, or vascular plant fragments were found in any of the intestines. In contrast, food-choice and growth experiments suggested that animal food (particularly Tubificidae and Chironominae larvae) was important in the tanypod diet. In the food-choice experiments, six different foods offered to small (4–7 mm long) and to large (8–12 mm long) larvae of Procladius choreus Meigen, were chosen in the following order: live Tubificidae spp.; detritus; live Chironominae larvae; a mixture of algae and diatoms; live Ostracoda spp.; and live Cladocera spp. However, when the results of the individual choices were examined, it was clear that the small larvae had consumed greater amounts of the small types of food (i.e. detritus, algae and diatoms) in comparison to the large larvae. In the growth experiment, those larvae of P. choreus reared solely on Tubificidae, detritus or Chironominae larvae thrived, while those fed on algae and diatoms, ostracods or cladocerans grew more slowly and fewer survived the experimental period.It was concluded that although Tanypodinae larvae are primarily predators with definite food preferences in ideal foraging conditions, in adverse conditions they will utilize a range of available stand-by foods, the most important of which appears to be detritus.     

Life cycle and production ofCladopelma virescens (Mg.) (Diptera: Chironomidae) in Lake Banyoles (NE Spain)

Life cycles and annual production of the chironomidCladopelma virescens are studied at two different depths in the sublittoral (5m) and the profundal (12m) zones of the karstic Lake Banyoles (NE Spain). Two generations were completed by this chironomid in the two sampling stations studied. Production was estimated with two different methods: increment-summation (IS) and size-frequency (SF). In the IS method the smoothed survivorship curves were estimated because of the absence of the smaller instars in the samples. The mean annual production varied from 44 to 70 mg m^–2y^–1 in the deeper station and from 215 to 270 mg m^–2y^–1 in the shallower, depending on whether the size-frequency or increment summation method was used. Annual P/B varied between 5.07 and 5.67, and 6.14 and 4.11 respectively. Due to the many assumptions to be made with the IS method, we suggest the SF method in this case, because the values given by the two methods are of the same order of magnitude.     

Life history and osmoregulatory ability of Telmatogeton amphibius (Diptera,Chironomidae) at Marion Island

Although the non-crustacean arthropod fauna of the intertidal zone in the sub-Antarctic is both diverse and abundant, little is known about the biology of the species that occur in this habitat. Here, we provide information on the biology and osmoregulatory ability of the marine intertidal midge Telmatogeton amphibius (Eaton) (Diptera, Chironomidae) at Marion Island. Larval densities of this species in the lower shore zones can be as high as 16,000 individuals m^–2 in their preferred habitat during peak abundance in summer. Winter abundances are substantially lower, and adults are much less abundant than larvae. Like other chironomids, this species has four larval instars and the flightless adult females have obligatory parthenogenesis. It is a strong osmoregulator. Larvae show little variation in body mass irrespective of whether they find themselves in freshwater or seawater, or are switched between the media. Haemolymph osmolality [ca. 400 milliosmol (mOsm)] varies by only 61 mOsm over a 1,520 mOsm range of the external medium. T. amphibius is similar in many respects to intertidal telmatogetonine midges found in other geographic regions.     

The identity of Dactylocladius commensalis (Diptera: Chironomidae) revealed

A new dipteran species, Parapsectra wagneri sp. n. (Chironomidae), is described from emergence traps on Breitenbach, Schlitz, Germany. It differs in antennal ratio and characteristics of the genitalia from the three known species.     

Life History of Bittacomorpha clavipes (Fabricius) (Diptera: Ptychopteridae) in an Ozark Spring,U.S.A.

A population of Bittacomorpha clavipes was studied in an Ozark spring from July 1987- August 1988. Measurement of larval head capsules (N=4,544) showed B. clavipes has four distinct larval instars. Seasonal distribution of immature and adult life stages suggests that this population has an asynchronous, non-seasonal, multivoltine life history with at least three cohorts. First instar larvae and pupae were collected during all months except December through March and December through February, respectively. Adults and larval instars II-IV were collected throughout the year. Larval recruitment generally paralleled adult flight periods, and the presence of adults during all months sampled indicates a correlation with ovipositional periods. The life history documented here for B. clavipes suggests that limiting factors for growth and reproduction are not seasonally dependent for this population.     

Feeding and sexual dimorphism in adult midges (Diptera: Chironomidae)

Adult chironomids feed readily on materials containing sucrose and glucose, and the addition of dyes is an easy way of demonstrating that food passes through the gut. Male and female flies are shown to make very different use of the food they take in. Males show no change in longevity but extend their flight time for an average of 160% over unfed males. Females, by contrast, show no detectable increase in flight time, but increase longevity by about 40%. Sexual dimorphism in the use of food seems appropriate to the roles of the sexes. We infer that males improve their swarming performance while females may benefit from increased longevity both in gaining time to find suitable mates and in the distance dispersed after mating. Males, and to a less extent females, are found on aphid infested trees near fresh water, and the suggested biological value of feeding is in sustaining the swarming flight especially for the males. Trichoptera adults are found feeding on aphid infested trees and the earlier findings that adult Trichoptera feed are confirmed.     

The larva and habitat ofParakiefferiella nigra Brundin (Diptera: Chironomidae)

Collections of adults ofParakiefferiella nigra Brundin indicate that this chironomid occurs widely in arctic and subarctic zones. In addition, it has occasionally been collected in cool temperate and boreal forest lakes of both North America and Europe. Although widely distributed, the larva and its habitat have not previously been described. Identity of the larva ofP. nigra has been established by studying associated reared specimens. The distinctive larva, with reduced second lateral mental teeth, is stenotopic, and on the basis of modern collections appears to be most abundant in cold, oligotrophic lakes. More data is required to establish the range of thermal environments inhabited by the larva. Larval head capsule remains ofP. nigra are common in late-glacial sediments of southwestern British Columbia lakes and provide important evidence for oligotrophic conditions during late-glacial time.     

Taxonomic review of the Pterostichini and Loxandrini fauna of New Caledonia (Coleoptera, Carabidae)

The generic-level taxa included in Pterostichini and Loxandrini from New Caledonia are reviewed and a key to genera and species provided. Two new genera are described, Paniestichus and Abacophrastus, with the following new species: Paniestichus subsolianus, Abacophrastus millei, Abacophrastus chapes, Abacophrastus carnifex, Abacophrastus hobbit, Abacophrastus megalops, Abacophrastus reflexus and Abacophrastus bellorum. Abacoleptus curtus new species, is described. Notonomus irideus and Notonomus savesi are moved to Prosopogmus. Four new species of Prosopogmus are described: Prosopogmus koghisensis, Prosopogmus lescheni, Prosopogmus fortis and Prosopogmus aoupiniensis. Homalosoma griseolum is moved to Sphodrosomus. Cerabilia is newly recorded from New Caledonia and the genus is moved from Platynini to Loxandrini and therefore is the first report of Loxandrini from New Caledonia. An apparent adventive from Australia, Darodilia, is newly reported from New Caledonia.