Chironomidae (Diptera) of Baldwin Lake,Illinois, a cooling reservoir

The chironomid fauna of Baldwin Lake, a closed-cycle cooling reservoir for a power plant, was sampled monthly to semi-monthly for one year at four stations, two in the discharge channel and two in the main basin. Qualitative samples were also taken elsewhere and with multiple-plate samplers. Twenty-four species were collected. Annual mean population density was less than 100 larvae m^–2 in the channel, 1037 M^–2 in the main basin. Three species of Tanypodinae formed over 96 percent of the larval population in the main basin: Tanypus stellatus Coquillett, Procladius bellus (Loew), and Coelotanypus concinnus (Coquillett). The principal species on the multiple-plate samplers were Dicrotendipes nervosus (Staeger), Glyptotendipes lobiferus (Say), and Parachironomus monochromus (Wulp). Temperatures of 35°C or more in the channel virtually eliminated the chironomids, whereas temperatures up to 32°C in the main basin increased the number of generations of T. stellatus from the usual two to four at Station 3 and three at Station 4. Station 3 had almost 1,000 degree-days more heat than Station 4.     

Biology ofChironomus piger Str. (Diptera: Chironomidae) and its role in the self-purification of a river

Chironomus piger larvae are widespread in small rivers and canals strongly polluted with domestic sewage. Despite this, almost nothing is known concerning the biology of the species under natural conditions and its role in the process of river self-purification. For two years, benthic samples were collected in the Sestra River at a site about 250 m downstream of the effluent discharge drains of a sewage treatment installation where the greatest concentrations of the larvae occurred. The number and biomass ofC. piger larvae were subject to marked fluctuations,viz. 96,000–348,000 ind m^–2 and 420–1,800 g m^–2. 460 degreedays (on average) was required for development of one generation.C. piger has 5 or 6 generations per year depending on the hydrometeorological conditions during the growing season.C. piger larvae play an important role in self-purification of the river. They utilize precipitating seston for food and for building their dwelling tubes. According to our calculations the amount of organic matter assimilated in the area of maximum larval concentration ranged 80–177 g wet weight m^–2 day^–1, and 32–71 g wet weight m^–2day^–1 was mineralized.     

Hanocladius,a new orthoclad genus from China (Diptera: Chironomidae)

Hanocladius longipes gen. nov., sp. nov. from Oriental China is described from the male imago. The long metatarsus, the very broad, scale-like virga and the conspicuously scalpellate acrostichals distinguish the genus from all of the known genera in Orthocladiinae.     

Two new nearctic species of small orthocladiinae (Diptera: Chironomidae) with notes on ecology

Two new species of chironomid midges (Rheosmittia arcuata n.sp. and Mesocricotopus loticus n.sp.) are recognized. They may easily be missed in collections due to their small size, and difficulty in collecting from the larval microhabitat (sand substrates for R. arcuata n.sp., low order streams with depositional substrates including gravel, sand, and silt for M. loticus n.sp.). Some morphological features are given to distinguish the new species from similar congeneric forms. The distribution and some ecological information for each species are also briefly discussed.     

Cytogenetic characteristics of a population of Chironomus riparius Meigen 1804 (Diptera, Chironomidae) from a polluted Po river station

A population of Chironomus riparius from a Po river station near Moncalieri (a trace-metal polluted station) was studied. In this population was established a great variability of band structure of polytene chromosomes as well as paracentric heterozygous inversions, deletions, deficiencies, partial breaks, diploid chromosome fragments, and changes in functional activity and appearance of heterochromatin. In arms A through F, some bands had an increased size compared to the standard chromosomic map. Some bands appeared in a heterozygous or normal homozygous state or were amplified. In all arms, many condensed stable bands appeared in the decondensed state when compared to the standard map. Asynaptic zones in arms E and G as well as heterozygous Balbiani rings and NORs were established. Very often the 4th chromosome was almost completely heteropycnotic and looded like a pompon chromosome. For the first time in this species, a high frequency of ectopic pairings of different arms was observed. Telomeric regions involved in ectopic pairings had a granular appearance, as did some centromeres. The hypothesis is advanced that such a high frequency of structural rearrangements could be correlated with genomic distribution of specific mobile elements.     

A new species of Dicrotendipes (Diptera: Chironomidae) from Costa Rica

The adult male of Dicrotendipes baru is described from the Dominical area of southwestern Costa Rica. The species is characterized by its elongate club-like superior volsella. This species represents the third member of the genus known from Costa Rica.     

Cytotaxonomy of Chironomidae (Diptera) from Lake Shabla (Bulgaria): cytogenetic evidence for introgressive hydribization

Twenty-two chironomid species were found in Lake Shabla. Five species (Chironomus bonus, Dicrotendipes lobiger, Kiefferulus tendipediformis, Cricotopus suspiciosus and Cricotopus sp.) are new for Bulgaria. Their karytopes are described for the first time.Cytogenetic studies of two closely related chironomid species, Glyptotendipes glaucus and G. pallens, show that in one area of sympatry (Lake Shabla, Bulgaria) about 2.5% of the naturally occuring individuals are hybrids. In most cases, in this hybrid, 1st, IInd and IIIrd chromosomes correspond fully to the chromosomes of G. glaucus. The IVth chromosome is a hybrid, with one homologue of the species G. glaucus; the other homologue is derived from G. pallens. Introgressive hybridization is of particular importance to the production of these combinations. Despite hybridization, natural selection appears to maintain the essential integrity of each separate gene pool.     

Distribution of Chironomidae (Insecta: Diptera) Head Capsules in Recent Sediments of Canadian Arctic Lakes

Thirty-two taxa of chironomid larvae were collected from the sediments of 50 lakes from across the Canadian Arctic Islands. Most chironomid taxa living in the Arctic have wide distributions, with only one taxon, Abiskomyia, showing a clear geographic limitation in this region. Many of these taxa have habitat preferences, among which lake morphometry, pH, nutrients and temperature are important. Due to the complex environmental patterns in the Arctic, lakes in both the northern and southern portion of the Canadian Arctic Archipelago have warmer temperatures and the chironomid assemblages of these two regions resemble each other more than those of the intervening central islands. Chironomid diversity is lowest in the central arctic islands, primarily Devon and Cornwallis Island, where the combination of low nutrients and cold temperatures provide the most severe environment for chironomid survival.     

A six-year study of abundance and voltinism of Chironomidae (Diptera) in an Illinois cooling reservoir

The chironomid fauna of Baldwin Lake, an off-stream closed-cycle cooling reservoir for an 1800-megawatt coal-fired power plant, was sampled semi-monthly to monthly at four stations for six years, beginning five months after the reservoir was filled and ending 23 months after the third unit of the power plant went into operation. In the main basin three species dominated: Coelotanypus concinnus (Coquillett), Procladius bellus (Loew), and Tanypus stellatus Coquillett. The last did not become established until the lake was two years old, probably because temperatures were too low the first winter. Populations of all three species were initially large and sharply fluctuating, but later became smaller and less fluctuant in C. concinnus and P. bellus, due, probably, to more intense predation on them. Only in T. stellatus were changes in voltinism clearly evident: it changed from bivoltine to tri- and quatrivoltine as degree-days of heat increased. Photoperiod also affected its life cycle, as evidenced by synchronous development of summer generations each year. Temperature and perhaps food supply affected development time of its overwintering generation. All three species tolerated a temperature of 38 °C; their populations were kept low in the discharge channel by the current, not the temperature. Six species of Chironominae were sporadically abundant in the discharge channel.     

Two new species of the orientalis group of Rheocricotopus (Psilocricotopus) from China (Diptera: Chironomidae)

Rheocricotopus (Psilocricotopus) calviculus sp. n. and R. (P.) villiculus sp. n. from China are described as male imagines. The species are closely related to the previously described R. (P.) orientalis Wang forming a new group, the orientalis group, which eventually may deserve the rank of subgenus or even genus. The group is distinguished by lacking a humeral pit, numerous sensilla clavata on third palpomere, cuneiform wings, no or few setae on squama, long legs, banded abdomen, very long inferior volsella, gonocoxite with apical extensions, and gonostylus with a median triangular projection.     

Natural establishment of a parasitoid complex on Bactrocera latifrons (Diptera: Tephritidae) in Hawaii

Bactrocera latifrons (Hendel) (Diptera: Tephritidae) is the most recent of four tephritid fruit fly species accidentally introduced into Hawaii. Although parasitoids have been released against other tephritid fruit fly species and have shown partial success in Hawaii, no parasitoids were released until 2004 to suppress populations of B. latifrons. The present study was conducted to document the parasitoid complex that has naturally established against B. latifrons in Hawaii and to assess whether there is a need for improving the biological control of this species. Based on ripe turkeyberry (Solanum torvum Sw) fruit collections over three consecutive years B. latifrons was the dominant tephritid fruit fly infestating turkeyberry at all four sites surveyed, across three major islands in Hawaii. The overall percentage parasitism of B. latifrons ranged from a low of 0.8% (Hana, Maui) to a high of 8.8% (Kahaluu, Oahu). Five primary parasitoid species were recovered from individually held B. latifrons puparia: Fopius arisanus (Sonan), Psyttalia incisi (Silvestri), Diachasmimorpha longicaudata (Ashmead), D. tryoni (Cameron), and Tetrastichus giffardianus Silvestri. F. arisanus was the predominant parasitoid at three of the four sites. Low levels of parasitism suggest that there is a need to improve biological control of B. latifrons, to minimize chances of this species causing economic impacts on crop production in Hawaii. We discuss the possibility of improving biological control of B. latifrons through augmentative releases of F. arisanus or introduction and release of specific and efficient new parasitoid species.     

Identification of instars and species in some larval Polypedilum (Polypedilum) (Diptera: Chironomidae)

Instars II and III of Polypedilum aviceps Townes, Polypedilum convictum (Walker), and Polypedilum illinoense (Malloch) can be identified to species by associating them with instar IV because key taxonomic characters remain relatively unchanged from instar to instar. Instars I cannot be identified to species or genus unless they are associated with older, identifiable larvae reared from the same egg masses. No single character evaluated on slide material can be used to clearly separate instars in all three species. Larvae of P. aviceps can be separated into instars based on any four of seven characters; P. convictum by either of two characters; and, P. illinoense by a combination of two characters. Changes in structures of instars II, III, and IV are described for all three species. Growth ratios for some structures are compared and discussed with regard to Dyar's Rule.     

A review of selected South- and East Asian Tanytarsus v.d. Wulp (Diptera: Chironomidae)

Male and pupa of Tanytarsus calorifontis sp. n. are described. Diagnoses, hypopygium drawings for the examined species and distribution are given for: Tanytarsus akantertiusSasa & Kamimura, T. angulatus Kawai, T. atagoensis Tokunaga,T. bathophilusKieffer, T. boninensis Tokunaga, T. formosae (Kieffer), T. formosanusKieffer, T. infundibulusChaudhuri & Datta, T. kikuchiiSasa, Kawai & Ueno, T. konishii Sasa & Kawai, T. mcmillani Freeman, T. mendax Kieffer, T. miyakobrevis Sasa & Hasegawa, T. monstrosus Chaudhuri et al., T. ogasaquartus Sasa & Suzuki, T. ogasatertius Sasa & Suzuki, T. okuboi Sasa & Kikuchi, T. oscillans Johannsen, T. ovatus Johannsen, T. oyamai Sasa, T. pollexus Chaudhuri & Datta, T. shouautumnalis Sasa, T. shoudigitatus Sasa, T. takahashii Kawai & Sasa, T. tamaundecimus Sasa, T. tonebeceus Sasa & Tanaka, T. tusimatneousSasa & Suzuki, T. unagiseptimus Sasa, T. uraiensis Tokunaga, T. yakuheiusSasa & Suzuki and T. yunosecundus Sasa. Tanytarsus ikiefeus Sasa & Suzuki is a new junior synonym of T. konishii. Tanytarsus ikifegeus Sasa & Suzuki, T. miyakoflavus Sasa & Hasegawa,T. oyabepallidus Sasa, Kawai & Ueno, T. simantoopeus Sasa et al. and T. tusimatheius Sasa & Suzuki are new junior synonyms of T. okuboi. Tanytarsus nippogregarius Sasa & Kamimura is a new junior synonym of T. bathophilus. Tanytarsus cultellus Chaudhuri & Datta and T. sibafegeus Sasa et al. are new junior synonyms of T. oscillans.Tanytarsus insulus (Guha et al., 1985) is a new junior synonym of T. ovatus. Tanytarsus sakishimanus Sasa & Hasegawa, T. vinculus Chaudhuri et al., T. parvistylus Chaudhuri & Datta, T. fusciabdominalis Guha et al. and T. euformosanus Kikuchi & Sasa are new junior synonyms of T. formosanus. Tanytarsus tsutaprimus Sasa, T. tokarajekeus Sasa & Suzuki, T. tusimatlemeus Sasa & Suzuki, T. tusimatopeus Sasa & Suzuki and T. yakugeheuus Sasa & Suzuki are new junior synonyms of T. shouautumnalis. Tanytarsus togasiroidus Sasa & Okazawa is a new junior synonym of T. shoudigitatus. Tanytarsus tusimatjekeus Sasa & Suzuki and T. tusimatkeleus Sasa & Suzuki are new junior synonyms of T. akantertius, and Tanytarsus tusimatpequeus Sasa & Suzuki is a new junior synonym of T. tusimatneous. Virgatanytarsus toganiveus (Sasa & Okazawa), Cladotanytarsus utonaiquartus (Sasa) and Zavrelia tusimatijeus (Sasa & Suzuki), all previously placed in Tanytarsus, are new combinations.     

A structural study of the anal papillae of the midge Chironomus riparius Meigen (Diptera: Chironomidae)

Larvae of the midge, Chironomus riparius Mg., have four anal papillae arranged as two pairs, one dorsal to and the other ventral to the anus. Structural study with light and electron microscopes has revealed that their integument consists of a thin cuticle overlaying a thick, syncytial epidermis which is specialised to facilitate ion transport. There is a distinct neck or collar region at the junction of each papilla with the rest of the body wall. Although in many respects these structures resemble those in mosquitoes, there are both morphological and physiological features which suggest that differences exist in the means by which ion exchange with the environment is controlled and effected in the two families.     

Seasonal dynamics of Chironomidae (Diptera) on the Bulrush Schoenoplectus lacustris in a chalk stream

SUMMARY. The chironomid fauna of a chalk stream in southern England is described from 1 year's catches of emerging adults and 2 year's quantitative samples of larvae on Common Clubrush, Schoertoplectus lacustris. The number of species in eaeh higher taxon as adult males and larvae on Schoenoplectus were: Tanypodinae, nine and three; Diamesinae, two for both; Orthoeladiinae, 26 for both; Chironomini. twelve and six; Tanytarsini, seven and five, respectively. A total of 66 species was recorded for both life stages. Adult Orthocladiinae were caught throughout the year. Tanytarsini were absent for a few weeks in winter, and Tanypodinae and Chironomini were caught for shorter periods in warmer months. Chironomids 93.5% of the total invertebrates on Schoenoplectus. Life histories are deseribed for seven speeies that formed 91% of the identified chironomids (32% of the total were unidentifiable first and second instar larvae). Four of these life histories appear for the first time. All seven species were multivoltine and had continuous recruitment for part of the year. The species diversity of larvae was mostly in the range 1.5–3.0 and it was determined more by equitability than by species richness. The numbers of chironomids through time were dependent on the weight of detritus on the leaves (r²= 0.69) and the availability of detritus therefore partly controlled their population size.     

Chromosomal variability in natural populations of Chironomus cingulatus meigen (Diptera, Chironomidae)

Chromosomal polymorphism has been studied in seven natural populations of Chironomus cingulatus from Western Europe, Western Siberia, and the Republic of Sakha (Yakutia). The banding sequences pool of the species includes 15 banding sequences. Chromosomal polymorphism was revealed in five out of seven chromosomal arms. Arm B is the most polymorphic with four banding sequences. There are three banding sequences in arm A. Arms D, E, and G have two banding sequences. None of the chromosome rearrangements were revealed in arms C and F. The populations of C. cingulatus differ clearly in their number and frequency of banding sequences, which indicates that different gene sequences are adaptive in different populations.     

Site specific differentiation in metal tolerance in the midge Chironomus riparius (Diptera,Chironomidae)

Metal tolerance in Chironomus riparius (Diptera) populations from contaminated streams was studied by comparing the effects of cadmium, zinc and iron on first generation laboratory reared midges. First instar larvae were exposed for four days, after which surviving larvae were counted and their length measured. Larvae from two highly polluted sites, kept under control conditions, grew substantially slower than those from other populations. All populations showed the same growth responses to increased zinc concentrations, but differences were found in the responses to both cadmium and iron. Since population differentiation was demonstrated in first generation laboratory animals, it is suggested that the differences between populations of C. riparius have a genetic basis.     

The role of glycogen during the ontogenesis of Chironomus anthracinus (Chironomidae, Diptera)

Large fluctuations in glycogen content were found in larvae, pupae and adults of Chironomus anthracinus (Zetterstedt) from the profundal zone of Lake Esrom, Denmark. In 2nd, 3rd and 4th instar larvae the glycogen concentration (expressed as percentage of dry weight) increased during periods of aerobic conditions to a maximum of 25%, but decreased in periods of hypoxia longer than two months to 10–12% in young larvae. A further decrease to about 5% took place, when moulting from 2nd to 3rd or from 3rd to 4th instar occurred after overturn. Prior to pupation the glycogen concentration was restored to 26–28%. The glycogen concentration approximated 22% in young pupae, but decreased during the pupal stage and newly hatched adults contained 12–15%. Finally, the glycogen store of both males and females was further reduced during the swarming period. Thus, glycogen seems to be an important energy source (1) during periods with hypoxic conditions, (2) during periods with high internal energy requirement such as ecdyses and metamorphosis, and (3) during the non-feeding adult life stage.     

New species of Oukuriella (Diptera: Chironomidae) from Costa Rica

The males of three new species of Oukuriella Epler are described from Costa Rica. The genus had been previously recorded only from South America. Oukuriella annamae sp. nov. has genitalia similar to O. albistyla Epler, but differs in having transverse bands on abdominal segments In, IV, VI and VII, a lower AR, no humeral setae and fewer dorsocentral setae. Oukuriella costaricense sp. nov. differs from other described species in the genus by its brown abdomen, unnotched posterior margin of tergite IX and distinctive superior volsella, with its sharply bent, thin upper arm directed medially, and digitus small and directed caudad. Oukuriella rushi sp. nov. has apices of femora tipped with brown, a brown abdomen and distinctive superior volsella, with upper arm shorter and broader, and digitus longer then O. costaricense. The female of Oukuriella costaricense is also described. This is the first female described for the genus. Based on male and female genitalia, Oukuriella is closely related to Epedilum Townes and Zavreliella Kieffer. A key is provided to separate the males of the six described species.