(1) Forcipomyia is one of the few genera of the Ceratopogoninae (Chironomidae) whose larvae are not aquatic. They retain, however, the apneustic condition typical of the entire family, and are therefore compelled to live in moist places such as beneath the rotting bark of fallen trees, in the hollow tap roots of dead plants, in wounds and rot holes in trees, in drying horse and cow manure, in decaying fungi, and in the nests of ants. The immature forms are strongly gregarious.

(2) The larvae pass through four stages, each lasting about a week; the successive changes in chaetotaxy at each moult is recorded in the discussion of F. picea. All known European species of this genus hibernate as third or fourth stage larvae. The duration of the pupal stage is about one week; the length of life of the adult has not been determined. There are usually three generations per annum. The adults are known to suck the blood of other insects.

(3) The larvae are eucephalous, more or less cylindrical, 3–6 mm. long, with eleven clearly denned segments (three thoracic and eight abdominal, the eighth divided into two apparent segments). Progression is achieved by means of a retractable, biramous, prothoracic pseudopod, and a ventral hook-studded ridge on the ultimate abdominal segment, with the occasional aid of the mandibles.

(4) The head and body bear numerous lanceolate and simple hairs of great specific importance.

(5) The mouth-parts consist of a fleshy labrum, a pair of small premandibles, a pair of long, slender mandibles working in the sagittal plane on either side of the labrum, a pair of reduced maxillae of fleshy nature with chitinous internal supports, and a simple untoothed labium. Within the head there is a complicated chitinous structure, the hypopharynx; this is figured and described in full detail and its action in comminuting the food is revealed for the first time.

(6) No investigation has hitherto been made of the internal anatomy. The alimentary canal, consisting of buccal cavity, hypopharynx, oesophagus, mid-gut, and hind-gut, is quite simple in structure, without nodules or caecal chambers. It is only slightly longer than the body, a loop occurring in the hind-gut when the larva contracts.

(7) The malpighian tubules are either two or three in number, the latter condition being unique among insects. The third is ventral, passing into the posterior part of the body only.

(8) The salivary glands are a pair of S-shaped bodies closely adhering to the walls of the anterior portion of the mid-gut; they are chiefly composed of large binucleate cells.

(9) The circulatory system consists of a dorsal vessel extending throughout the body and passing between the lobes of the brain above the oesophagus into the head. In the eighth abdominal segment it enlarges slightly to form the heart, with one pair of ostia or valves situated on its posterior extremity.

(10) The nephrocytes are arranged segmentally, four to each abdominal segment and a single mass in the thorax, all attached to the dorsal vessel. The excretory function of these cells was demonstrated by injection of ammonia-carmine into the body cavity.

(11) The nervous system is only very slightly cephalised, there being seven ganglia for the eight abdominal segments and three in the thorax; the normal bilobed brain is situated in the thorax in all larval stages. The sympathetic system is described, and differs somewhat from that of its close relative, Chironomus.

(12) Despite the absence of spiracles there is a well-developed tracheal system in the form of two main trunks with transverse connections, branch tracheae, and subcutaneous plexuses.

(13) The muscular system, oenocytes, fat-body, and gonads have also been studied in detail.

(14) The larval skin is retained upon the last four or five abdominal segments of the pupa.

(15) The characters used for determining the species, in their order of importance, are as follows: Larva: chaetotaxy, prothoracic pseudopod, markings of the head, anal blood-gills. Pupa: cuticular spines, prothoracic horns.

(16) The larvae and pupae of nine species of Forcipomyia are described with particular reference to their specific characters. Descriptions of the adults of two new species, F. radidcola and F. pulchrithorax, by Mr F. W. Edwards, are appended.

(17) Closely related forms are Euforcipomyia and other exotic subgenera not yet named, and the genus Atrichopogon (now including Kempia). Dasyhelea belongs to this group of hairy-winged flies, but its larvae partly resemble those of the bare-winged Ceratopogonines in that they have lost the pro-thoracic pseudopod and macrochaetae, but retain the anal hooks.

A simple method is described for eliminating the symbionts from the body louse during the egg stage, and thus producing symbiont-free larvae. The behaviour of lice freed of their symbionts by this method is described and compared with that of lice freed of their symbionts by extirpation of the larval mycetome.

The complete accord of the results obtained by the different methods warrants the conclusion that the symbionts play an essential role in the life of the louse, so much so that without them death of the larvae results. It is, therefore, justifiable to consider this relationship true symbiosis.

The diversity in a 925 bp portion of the Plasmodium vivax MSA1 gene in isolates from the Philippines, China, the Solomon Islands and Papua New Guinea was investigated. A total of 74 base pair changes was found in the amplified fragment from 18 isolates. Most of these changes were single or double base pair substitutions. In several regions, these point changes were tightly linked with one set always present or always absent in the different isolates. Seven such blocks were identified. These blocks were present in different combinations in the different isolates indicating that extensive intragenic recombination has occurred.

1. Optimum growth of E. invadens occurred in HSre + S in the presence of Bact. coli, at 24–30° C. The amoebae could not be ‘trained’ to grow above 35° C.

2. The amoebae ingested normal rat erythrocytes, but not those of chick or frog.

3. Mass encystation occurred only under conditions which favoured the growth of the amoebae, but was not dependent on an acceleration in growth rate; in certain strains, an increased production of cysts was correlated with the depletion of starch in the medium.

4. The amoebae were always killed by treatment with N/20-HCl for 1 hr. at room temperature, although usually they did not survive after treatment for only 10 min. At room temperature, the cysts survived treatment with N/10-HC1 for at least 6 days, and with 0·002% HgCl2 for at least 4 hr.

5. The amoebae of E. invadens were adversely affected by aerobic conditions.

6. The amoebae could survive for up to 35 days at 8° C. but for not more than 7 days at 37° C. The cysts survived for at least 14 days at 8° C., for 7, but not 11, days at 24° C., and for less than 7 days at 37° C.

7. It is suggested that, in view of the morphological identity of E. aulastomi, E. invadens, E. moshkovskii and E. histolytica, and the fact that the amoebae of these groups form a series growing at increasingly higher temperatures, these four organisms constitute subspecies rather than full species. The taxonomic status of E. ranarum is still open to question.

The ability of five staining techniques, originally developed for the rapid identification of Cryptosporidium spp. oocysts in faecal samples, to detect oocysts in water and water-related samples was assessed. All the stains used (modified Ziehl Neelsen, auramine-phenol (Lempert), Wright-Giemsa, safranin-methylene blue and FITC-labelled monoclonal antibody) stained oocysts after storage in water for 2 months at 4 °C (71–89 % of control values). Storage of oocysts below 0 °C greatly reduced the staining ability of auramine-phenol. With the exception of oocysts stored in raw and final waters, the histochemical stains proved less useful in detecting oocysts than the monoclonal antibody. Organisms of similar size and shape took up these stains, causing confusion in interpretation. Cold Ziehl Neelsen and the FITC-labelled monoclonal antibody were best at identifying oocysts from a waterborne outbreak. Screening with a fluorescent antibody, followed by confirmation with cold Ziehl Neelsen, where possible, are the currently recommended procedures for the detection of oocysts in water-related samples.

The localization and distribution of neuropeptides and an indoleamine (serotonin or 5-hydroxytryptamine) in the enteric nervous system (ENS) of the pig roundworm, Ascaris suum, have been determined by the application of an indirect immunofluorescence technique in conjunction with confocal scanning laser microscopy. Whole-mount preparations of pharyngeal, intestinal and rectal regions were screened with antisera to 23 vertebrate peptides, 2 invertebrate peptides and serotonin (= 5-HT). Positive immunoreactivity (IR) was obtained with antisera to pancreatic polypeptide (PP), peptide YY (PYY), FMRFamide, gastrin and serotonin. The only IR observed in the ENS was that evident in the nerve supply to the pharynx and rectal region; no IR was associated with any region of the intestine. The most extensive patterns of IR occurred with antisera to PYY, FMRFamide and serotonin. In the pharyngeal component of the ENS, IR was evident in the lateral and dorsal longitudinal pharyngeal nerves, pharyngeal commissures, nerve plexus, and associated nerve cells and fibres. In contrast, the distribution of IR to the PP and gastrin antisera was more restricted and displayed a lower intensity of immunostaining. The other component of the ENS, the rectal enteric system, only yielded immunostaining to FMRFamide. The possible role of neuropeptides and serotonin in the nutritional biology of nematodes is discussed.

Excretory/secretory (ES) products obtained by in vitro culture of infective-stage larvae of Trichinella spiralis and T. pseudospiralis were injected intramuscularly at various intervals into mice. Mini-osmotic pumps containing T. spiralis ES products were also implanted subcutaneously and intraperitoneally into rats. The introduction of ES materials into muscles elicited extensive lesions which included dissolution of myofibres, mobilization of mononuclear and polymorphonuclear leucocytes, angiogenesis, hypertrophy of myonuclei, myotube formation, mitosis, muscle bundles becoming rounded and separated from each other, disappearance of Z, I and A bands of sarcomeres, increase in endoplasmic reticulum and Golgi complexes, decrease in glycogen and relocation of mitochondria. These are considered as degenerative/regenerative changes of muscles to injury. Immunodominant epitopes of specific 45–53 kDa glycoproteins in ES antigens of T. spiralis could not be detected in hypertrophic nuclei of injected muscles by using polyclonal and monoclonal antibodies and immunocytochemical methods. ES products of T. spiralis failed to stimulate unsensitized lymphocytes in the lymphocyte transformation test. Infective-stage larvae of T. spiralis released from muscles were found capable of forming nurse cells after injection subcutaneously into rats. It is postulated that the invasion of muscles by trichinellids elicits two independent events, i.e. a general degenerative/regenerative response of muscles and a specific change in genomic expression of myonuclei. The two events are probably mediated by different effector molecules.

Leptocotyle minor is a monogenean parasite specialized for living on the denticlecovered skin of the dogfish Scyliorhinus canicula. Each adult parasite attaches itself to the outer surface of a single denticle. Small postlarvae are found on the inner surfaces of the denticles. The denticles have hard enamel on both inner and outer exposed surfaces. Haptoral hooks, such as are present in other monogenean oncomiracidia, would be unable to penetrate this hard surface and are absent in postlarval and adult parasites which attach themselves by cement. The oncomiracidium possesses six haptoral spicules which may be homologues of the marginal hooks of other monogeneans, but these spicules disappear early in postoncomiracidial development.

Adult parasites feed on the host's epidermis which lies between the denticles. The position of small postlarvae on the inner surfaces of the denticles enables them to reach the epidermis for feeding purposes. Growth then permits young parasites to migrate away from the epidermis on to the outer surfaces of the denticles.

Adult parasites move from one denticle to another in a leech-like manner, and copulation occurs between parasites which meet as a result of these movements.

I am grateful to the Director and Staff of the Plymouth Laboratory for their hospitality and particularly to Mr J. E. Green for his interest and co-operation.

Experiments using chicks of specified strain, age and sex raised under identical conditions on the same diet and infected with known strains of coccidia are described. The relationships between the infection rates and resulting oocyst productions of Eimeria acervulina and E. tenella are presented graphically and are used to demonstrate a crowding effect. Possible contributory factors to the crowding effect and possible reasons for the differences between the E. acervulina oocyst production of unmedicated birds or birds medicated with decoquinate are discussed. It is suggested that standard curves for normal infection rate — reproductive potential relationships under strictly specified conditions may be of value in choosing appropriate infection rates for critical experimental work to assess the effects of anticoccidial compounds on oocyst production.

1. The availability of Nematodirus infection to sheep was followed by grazing successive pairs of worm-free lambs on a contaminated plot. It was shown that lambs did not become infected during the summer following pasture contamination in the spring, but became infected when they were grazed on the plot the following spring.

2. The development and hatching of the eggs and larval stages of N. battus and N. filicollis were followed by the periodical examination of infected faeces set out during May-November. The results showed that development to the infective larval stage occurred during the summer, taking normally about 3 months, but that the larvae then remained dormant within the egg membranes until the following spring.

3. Laboratory studies confirmed the hypothesis that the hatching of the infective larvae was a response to a rise in temperature in the spring, following sensitization by exposure to low temperature during the winter. A rise in temperature to 50° F. was necessary before a high percentage hatch occurred.

4. The epidemiology of Nematodirus infection is discussed in relation to these observations.

Enzymes moonlight in a non-enzymatic capacity in a diverse variety of cellular processes. The discovery of these non-enzymatic functions is generally unexpected, and moonlighting enzymes are known in both prokaryotes and eukaryotes. Importantly, this unexpected multi-functionality indicates that caution might be needed on some occasions in interpreting phenotypes that result from the deletion or gene-silencing of some enzymes, including some of the best known enzymes from classic intermediary metabolism. Here, we provide an overview of enzyme moonlighting in parasitic protists. Unequivocal and putative examples of moonlighting are discussed, together with the possibility that the unusual biological characteristics of some parasites either limit opportunities for moonlighting to arise or perhaps contribute to the evolution of novel proteins with clear metabolic ancestry.

This paper describes patterns of infection with Opisthorchis viverrini within a human community assessed by egg count, parasite-specific antibody levels and worm burden determined by expulsion chemotherapy. All three measurements increased significantly with age, reaching a plateau in young adults. There were no significant sex-associated differences in the prevalence or intensity of infection, antibody levels, or in the frequency of heavy worm burdens. A striking 81·5% of the total Opisthorchis population and 74% of the total egg output were expelled by the most heavily infected 10% of the humans sampled. This extreme over-dispersion, together with recent findings that hepatobiliary disease frequently accompanies heavy infections, argues that the priority for community-based parasite control programmes should be to maximize treatment and health promotion efforts toward heavily infected individuals.

An account is given of the seasonal occurrence, maturation and population changes of Caryophyllaeus laticeps in its intermediate host Psammoryctes barbatus and in its definitive host Leuciscus leuciscus in the River Avon. Infective larvae were found in the tubificid in all months except August, but occurrence and maturation of C. laticeps in fish showed a clear seasonal periodicity. Infections were acquired between December and March, the parasite matured in April and May and disappeared by July. Maturation of C. laticeps appeared to be governed by changes in fish hormone levels. Changes in the parasite population in fish bore no relationship to the availability of infective larvae nor probably to the feeding behaviour of fish but were closely correlated with water temperature changes. The most important factor controlling the dynamics of the C. laticeps–dace system appears to be a temperature dependent rejection response to the parasites by dace, and it is suggested that a similar mechanism may operate to control the dynamics of other freshwater fish–tapeworm systems.

I should like to thank the Avon and Dorset River Authority, and in particular Mr A. S. Grater, for their help in capturing the fish and for their ready co-operation.

Praziquantel is widely used for the treatment of human schistosomiasis. However, in recent years, there has been increasing concern about the resistance of Schistosoma species to praziquantel. The study described here was designed to evaluate the current susceptibility to praziquantel in S. japonicum in China. During the non-transmission period of schistosomiasis, a random sample of 4760 subjects from the main endemic foci of China were examined using parasitological stool examination. In total, 584 subjects were identified as being infected with S. japonicum, with a prevalence rate of 12 27%. Among them, 565 stool-egg-positive subjects were treated with praziquantel in a single oral dose of 40 mg/kg. Six weeks post-treatment, among the 505 villagers re-examined, 480 (95 05%) had no detectable S. japonicum eggs. Twenty-one subjects still excreting eggs after the first treatment were treated with praziquantel for the second time. All stool samples, including those from those participants with second treatment were re-examined 6 weeks after the second treatment, and no stool-egg-positives were found. The results indicate that the current efficacy of praziquantel against S. japonicum is still high and has not changed after more than 2 decades of repeated, expanded chemotherapy in the main endemic areas of China. It is suggested that no evidence of tolerance or resistance to praziquantel in S. japonicum was detected in China.

Observations that growth of Plasmodium falciparum in vitro is inhibited by high temperatures have led to hypotheses that malaria fever may influence the parasite population dynamics, regulating parasite density and synchronizing parasite growth. In order to investigate the fever hypotheses, we have developed an age-structured coupled Markov chain model that describes the parasite erythrocyte cycle and its interaction with the host fever response. We estimated the model parameters using data collected from laboratory parasite cultures that were exposed to febrile or normal temperature. Using the experimental parameter values, quantitative predictions were made of the effect of fever in determining the parasite population dynamics. It was concluded from the model behaviour that, during the primary infection of a non-immune host, a typical episode of fever can effect density-dependent regulation of the parasite population, maintaining cycles of parasitaemia and promoting synchronous parasite growth.

Plasmodium falciparum merozoites have an array of 2–3 subpellicular microtubules, designated f-MAST. We have previously shown that colchicine inhibits merozoite invasion of erythrocytes, indicating a microtubular involvement in this process. Colchicine inhibition of invasion was reduced by the Taxol®-stabilization of merozoite microtubules prior to colchicine exposure. Immunofluorescence assays showed that the number and length of f-MASTs were reduced in colchicine-treated merozoites, confirming that microtubules were the target of colchicine inhibition. The dinitroaniline drugs, trifluralin and pendimethalin, were shown by immunofluorescence to depolymerize the f-MAST and both drugs were inhibitory in invasion assays. These results demonstrate that the integrity of the f-MAST is important for successful invasion. Fluorescence imaging demonstrated the alignment of mitochondria to f-MAST, suggesting that mitochondrial transport might be perturbed in merozoites with disorganized f-MAST. Depolymerizing mt in late-stage schizonts did not affect the allocation of mitochondria to merozoites.

On the basis of partial amplification of a cloned fragment of kDNA of Leishmania infantum which is specific for this species, we developed a PCR–ELISA technique which avoids the problems associated with classical diagnostic techniques. This technique was tested on 33 L. infantum strains from 19 different zymodemes, which were recognized equally. It was also used on human and canine clinical samples. PCR–ELISA has a higher sensitivity than the other techniques used (IFAT, parasite cultures, optical microscopy of stained samples) and permits detection of a minimum of 0.1 promastigotes or 1 fg of genomic DNA. PCR–ELISA can be used to diagnose human cutaneous leishmaniasis using material obtained by scraping the lesion margin, and human visceral leishmaniasis in HIV(+) individuals and canine leishmaniasis with peripheral blood samples. The presence of L. infantum in dogs with low antibody titres with IFAT technique (20 and 40) was demonstrated indicating that seroprevalence data from epidemiological studies underestimate the true rates of infection.

1. The r.q. of whole Neoaplectana glaseri rose from 0·56 to 1·10 when glucose was added to the medium. The Qo2 was only slightly affected. Respiration of other nematode parasites was largely unaffected by exogenous glucose. Pyruvate had little or no effect.

2. Inorganic phosphate increased when Ascaris lumbricoides muscle brei was incubated. In the presence of fluoride, or when aqueous extracts were used, easily and difficultly hydrolysable phosphate was formed. Phosphatase activity was dominant even in aqueous extracts of A. lumbricoides intestinal tissues and fluoride inhibited Po formation only slightly. Ptot., and PresIdual fell markedly in whole A. lumbricoides which had been incubated anaerobically. Under aerobic conditions Po fell slightly, but the other components rose considerably. Phosphorylative activity of A. lumbricoides ovary was greater than in the muscle. Phosphorus compounds in perienteric fluid did not change during incubation.

3. The breakdown of glycogen and the formation of glucose in aqueous extracts of Ascaridia galli was inhibited by fluoride and phloridzin. Polysaccharide was synthesized in fluoride-poisoned preparations when glucose 1-phosphate was added. Polysaccharide formation in Ascaris lumbricoides fluoridepoisoned muscle preparations was demonstrated without the addition of Cori ester.

4. Fructose 1:6-diphosphate added to aqueous extracts of Ascaridia galli and Nematodirus spp. was rapidly metabolized at pH 6·5. At pH 7·2 the fructose content increased.

5. In aqueous extracts of Nematodirus or Ascaridia brei which had been autolysed for short periods, 55–60% of the glycogen utilized appeared as glucose. Only small amounts of lactate were formed. Aqueous extracts of Nematodirus and Ascaridia brei which had been autolysed for long periods formed glucose in excess of the glycogen disappearing. When perienteric fluid, which contained amylase, was removed from A. galli before autolysis, the amount of glucose formed was very much reduced. It is suggested that the excess glucose was formed from dextrins which were not estimated as glycogen and which were hydrolysed by perienteric fluid amylase during incubation.

Lactate decreased during the incubation of extracts prepared from brei which had been autolysed for long periods.

6. Bicarbonate decreased during the anaerobic incubation of aqueous extracts of Nematodirus spp. and Ascaridia galli which were buffered with CO2-bicarbonate. The decrease in bicarbonate was in excess of the CO2 expelled from the medium by acid formation.

7. The acid-soluble phosphorus compounds of the different tissues of Ascaris lumbricoides were examined. Compounds similar to a.t.p. were found in the intestine, ovary, muscle and possibly also in the perienteric fluid. The acid-unstable phosphorus compounds did not appear to be either creatine- or arginine-phosphate. Compounds similar to Embden ester were found in the ovary and muscle. The occurrence of the phosphate compounds found in the parasite is compared with figures given for other organisms.

8. It is concluded that carbohydrate fermentation as far as lactate in nematode parasites was similar to that found in yeast and mammalian muscle. Energy was transferred by means of high-energy phosphate bonds.

9. Phospholipids, which were found in considerable amounts in the tissues of A. lumbricoides, were estimated as lecithin, sphingomyelin and serine- and ethanolamine-containing phospholipids. The amounts of the phospholipids found in the parasite tissues are compared with figures given for other organisms.

The authors are deeply indebted to Prof. D. Keilin and Dr T. Mann of the Molteno Institute, Cambridge, for their advice and critical reading of the manuscript. Thanks are also due to Dr E. F. Gale and Dr E. Friedemann for advice on analytical procedures.

The effect of host resistance on the feeding and development of Rhipicephalus appendiculatus, the African brown ear tick, was investigated. In this 3-host species the percentages of larvae and nymphs engorging on resistant cattle, and also of those subsequently moulting, were significantly less than those of ticks feeding on susceptible rabbits (i.e. without previous tick-feeding experience). The mean weights of engorged larvae, nymphs and females were significantly reduced on resistant hosts. Fewer nymphs and females engorged, even when fed on susceptible hosts, if their previous feed had been on a resistant host, and the engorged weight was also less. If only one feed during the life-cycle was on a resistant host the final egg production was reduced by a factor of 13· 2· and l· for the larval, nymphal and adult feed respectively. The egg production of a tick population with all 3 stages feeding only on resistant hosts could be reduced by more than 98% if these effects were combined.