1. Phaonia mirabilis eggs are laid on the surface of water in tree holes. The eggs are white and have lateral flanges and a ventral keel.

2. Trimorphism is absent during larval life, and, except for size, the newly hatched larva resembles the mature larva, having anterior spiracles, triforous posterior spiracles and complete buccal armature.

3. The larvae are carnivorous and capture and devour mosquito larvae.

4. Eggs hatch in 3–4 days. The duration of larval life is about 4 weeks and that of the pupal stage about 2 weeks.

Eight days after mother rats were injected with 4000 infective larvae of Strongyloides ratti at different stages of lactation the numbers of adult worms in their intestines were uniformly low (< 3% of the dose) compared with unmated controls (mean = 25%). Those in their litters varied from 12% on day 5 to a maximum of 47% on day 17 post partum. These data, which do not correlate with lactational performance, imply that parasite movements in lactating rats are controlled by qualitative, not quantitative, consequences of humoral events. The numbers of worms in litters are concluded to be the result of the interaction of dynamic determinants of larval routes in the mother and changes in the suitability of the neonatal gut as an environment for worm development. The timing of events leading to milk-borne infection is defined. Injected larvae were closely synchronized in their movements, which were completed in 36 h. Larvae experimentally diverted into the mother's tissues during her first lactation were not available for the infection of a second litter.

The state of Yugoslavia provides both an abundant and important source for zoological studies owing to its varied geographical, climatic and ethnographic conditions. To the student of ticks especially there is hardly a country in Europe which offers as large a field for study as Yugoslavia. Therefore I trust a short description of the Yugoslavian ticks and their biological habits, so far as known, will be of some interest.

Host nutrition plays a major role in the nutritional physiology of Trichoplusia ni parasitized by the hymenopterous insect parasite, Hyposoter exiguae. Severely reduced growth rate characterized the host association throughout the 4th developmental stadium. This effect of parasitization, however, was indirect and growth depression of parasitized larvae was entirely accounted for by the accompanying decreased rate of food consumption. Parallel-fed larvae, that is, unparasitized larvae feeding on nutrients at the same rate as observed in ad libitum-fed parasitized individuals, displayed lower rates of growth than parasitized larvae and the latter had higher rates of assimilation. Parasitization, therefore, directly resulted in an increased rate of assimilation over that observed in uninfected insects after accounting for the effects of altered food consumption. Similarly, differences in the pattern of response to decreased dietary protein levels between parasitized and unparasitized insects could be explained on the basis of differences in their rates of food consumption

Mixed infections with malarial (Plasmodium gallinaceum) and filarial (Brugia pahangi) parasites were carried out in 8 trials with filaria susceptible (REFM) and filaria refractory (REP-RR) Aedes aegypti strains. A secondary infection with B. pahangi microfilariae (mff) by intrathoracic inoculation, reduced the development rate of a pre-existing P. gallinaceum infection. The level of reduction ranged from 9·5 to 49% in REFM and from 50 to 90% in REP-RR. An immune response against oocysts was seen as melanization in mosquitoes with a double infection in the strain refractory to B. pahangi (REP-RR) and a reduction in oocyst size in both mosquito strains. Melanization was not observed in mosquitoes infected only with P. gallinaceum. This may indicate that activation of the prophenoloxidase (PPO) cascade in response to mff in the haemolymph can also be addressed against oocysts in the midgut. No significant difference in the number of filarial parasites recovered was observed when comparing groups with a single or double infection. Retardation in development of filaria larvae was observed in mosquitoes with double infection (REFM strain), together with melanization and a higher rate of abnormal development. Nutritional deficiency caused by superinfection might also be responsible for the delay in filarial development and reduced oocyst size.

In the course of an inquiry into the relation between the bionomics of certain insects and epidemic disease upon which I am engaged, the following question suggested itself to me. In the event of a larva becoming bacterially contaminated by means of its food, is it possible that the resulting pupa and imago will still be infected? The only previous work bearing upon this question with which I am acquainted is that of Faichnie, who writes:

1. Formulae developed by Anfinsen et al. (1946) for a medium used in the cultivation of Plasmodium knowlesi were used for media in which excystation of Entamoeba histolytica without bacteria was investigated.

2. The following media were used: (i) an inorganic fluid containing carbon dioxide and chlorides, phosphates, and bicarbonates, of sodium, potassium, magnesium, and calcium; (ii) an inorganic fluid of chlorides and phosphates of the above metals without bicarbonates; (iii) the same respective fluids plus glucose, and (iv) the same plus enrichments with B vitamins, cocarboxylase, vitamin C, purines, pyrimidines, folic acid, glucosamine, cholesterol, and amino-acids. The oxygen content of all media was lowered either by cysteine or glutathione.

3. Some excystation occurred in all media, the percentages were lowest in the inorganic fluid without bicarbonates, highest in fluid with bicarbonates plus all of the listed organic compounds, and intermediate in the inorganic bicarbonate fluid plus glucose. Amino-acids were not required for good percentages of excystation.

4. Excystation occurred when cysts were isolated in medium with Trypanosoma cruzi.

5. The data show that organic compounds in the medium are necessary for high percentages of excystation.

Genetic exchange is now known to occur during the life-cycle of many parasitic protozoa, including malaria parasites, coccidia and trypanosomes. The process is studied by making deliberate crosses between cloned organisms differing in clearly defined markers. In malaria parasites, crosses have been made between parasites differing in characters such as isoenzymes, antigens and other proteins, drug sensitivity, and chromosome and other DNA polymorphisms. Crosses are made by transmitting a mixture of gametes of each clone through mosquitoes to allow cross-fertilization to take place, and examining the resulting progeny by cloning for organisms exhibiting non-parental combinations of characters. The inheritance of many characters, such as antigen and protein variants, is in accordance with Mendelian expectations for a haploid organism. Recombination occurs at a higher than expected frequency. Studies on chromosomes have show that crossing-over events commonly occur following meiosis of hybrid zygotes. Repetitive DNA and subtelomeric regions of chromosomes appear to be particularly susceptible to such recombination events. In trypanosomes, crosses between clones of Trypanosoma brucei have shown that hybrids are formed during tsetse fly transmission. The organism appears to be mainly diploid, but some characters including certain chromosomes seem to be inherited in a non-Mendelian manner.

Surface aminopeptidase (APase) in the acanthocephalan, Moniliformis dubius, was studied using leucylleucine, leucylglycylglycine, glycylglycine, alanylalanine, tri-alanine and tetra-alanine as substrates. In the presence of intact worms all peptides, except glycylglycine, were hydrolysed liberating amino acids and/or peptide subunits into the incubation medium. In 5 min incubations with 5mM leucylleucine, 93% of the liberated leucine was absorbed by the worms indicating a kinetic advantage for absorption of the leucine. In media with leucylleucine plus 10 mM methionine as an inhibitor of leucine uptake, the liberated leucine was not absorbed by the worms, but accumulated in the incubation medium.The inhibitory effects of leucylleucine and alanylalanine (or products of hydrolysis) on the uptake of 0·1 mM [14C]leucine in 2 min incubations were examined. Inhibition of [14C]leucine uptake by these peptides was non-linear up to 5 mM inhibitor concentration. Concentrations of either peptide greater than 5 mM did not produce further inhibition. A significant portion of [14C]leucine transport was not inhibited by these peptides. Inclusion of 0·5 mM Pb2+, an APase inhibitor, blocked the inhibition of [14C]leucine uptake by leucylleucine indicating that the inhibition is caused by the liberated leucine alone, and that interaction of the intact dipeptide and the leucine transport system is negligible.It is concluded that the surface membrane of adult worms has APase which can hydrolyse peptides in the ambient medium. The spatial arrangement of the APase and the leucine transport system is such that the hydrolysis of a peptide confers a kinetic advantage for absorption of the liberated amino acids.Encysted or mechanically excysted cystacanth larvae from the haemocoele of the cockroach showed no APase activity. Activation of the APase required a 30 min treatment in lipase, [Na+]taurocholate or other surface active agents. Since the APase in adult worms was unaffected by washing, the data strongly suggest that this enzyme is of parasitic origin.

1. Experiments are described in which various concentrations of pyrethrum in oil are tested for speed of stimulation of Ornithodorus larvae. There is a logarithmic relation between concentration and speed of stimulation, except with concentrated solutions (stronger than 0·015% by weight of pyrethrin I) in which there is a relative retardation of response.

2. As larvae grow older they respond more slowly, and this is probably due to an increase in thickness of the cuticle in natural growth.

3. Mineral oils induce much swifter penetration of the pyrethrum than any of the vegetable oils tested.

My thanks are due to Prof. Buxton in whose department the work was done, and also, to Dr J. T. Martin of Rothamsted Experimental Station, who kindly analysed samples of Pyremist ‘L’ for pyrethrin I.

LLC-MK2 cell monolayers infected with Trypanosoma cruzi were shown by immunofluorescence to present parasite antigens on the surface of both parasitized and non-parasitized cells after completion of the first intracellular cycle and rupture of infected cells. The cell-culture supernatant fluid at this stage, as well as the supernatant fluid of parasites left overnight in culture medium were concentrated and contained antigen capable of binding to uninfected cell monolayers. The origin of this antigen, as well as its eventual role in the pathogenesis of Chagas' disease, are discussed.

In 1835 Westwood described Nycteribia sykesii and N. hopei, and mentioned the possibility of both being male and female of the same species. He also described N. dubia. In 1860 Bigot described N. oxycephala. In 1863 Kolenati created the genus Cyclopodia for N. sykesii and N. hopei, but did not include N. dubia in the new genus. Kolenati did not see any specimens, but based his diagnosis solely on Westwood's figures and very short descriptions. In 1878 Rondani described C. albertisi and N. ferrarii. In 1884 Karsch described C. greeffi and in 1889 de Meijere described C. horsfieldi. All these descriptions, except that of C. horsfieldi, are incomplete, and the first paper dealing in detail with ten species, of which four were new, is Speiser's monograph of 1901. Since then only three species have been described (C. inclita Falcoz, 1927; C. pembertoni Scott, 1932; and C. tenuis Schuurmans Stekhoven & Hardenberg, 1938). Speiser re-defined the genus. He mentioned the pigmented eyes with two ocelli, the broad antennae, the long anterior coxae and the three rings on the tibiae.

The prevalence of patent schistosome infections of intermediate host snails often shows seasonal variations. For schistosome, mainlySchistosoma haematobium, infections of Bulinus globosus field data from Zimbabwe show annual ranges in prevalence from 2% to 30%. In this paper a mathematical model is developed for B. globosus population dynamics and the epidemiology of schistosome infection. The model is a discrete-time analogue of a catalytic model, with an added recruitment term. Snail fecundity and survival are functions of age, infection, and temperature. The pre-patent period of infection is dependent on temperature.Parameter values, and relationships with temperature, are taken from earlier field and laboratory studies. The force-of-infection is estimated from analysis of age-prevalence data. Model predictions, making use of temperature data recorded in the field, are in good agreement with observations over a 2-year period at a study site in Zimbabwe. The key features of interest are a fall in the prevalence of patent infections during the cold season and a rapid rise to a peak early in the hot season. This pattern results from the accumulation of pre-patent infections which fail to develop at low temperatures, but mature en masse, together with new infections, after a few weeks at higher temperatures. Model analysis demonstrates that seasonal patterns in the prevalence of patent infections may be due largely to the influence of temperature on the pre-patent period. Seasonal and year-to-year variations in temperature may therefore have significant epidemiological effects.

Obligately intracellular microsporidia regulate their host cell life cycles, including apoptosis, but this has not been evaluated in phagocytic host cells such as macrophages that can facilitate infection but also can be activated to kill microsporidia. We examined two biologically dissimilar human-infecting microsporidia species, Encephalitozoon cuniculi and Vittaforma corneae, for their effects on staurosporine-induced apoptosis in the human macrophage-differentiated cell line, THP1. Apoptosis was measured after exposure of THP-1 cells to live and dead mature organisms via direct fluorometric measurement of Caspase 3, colorimetric and fluorometric TUNEL assays, and mRNA gene expression profiles using Apoptosis RT2 Profiler PCR Array. Both species of microsporidia modulated the intrinsic apoptosis pathway. In particular, live E. cuniculi spores inhibited staurosporine-induced apoptosis as well as suppressed pro-apoptosis genes and upregulated anti-apoptosis genes more broadly than V. corneae. Exposure to dead spores induced an opposite effect. Vittaforma corneae, however, also induced inflammasome activation via Caspases 1 and 4. Of the 84 apoptosis-related genes assayed, 42 (i.e. 23 pro-apoptosis, nine anti-apoptosis, and 10 regulatory) genes were more affected including those encoding members of the Bcl2 family, caspases and their regulators, and members of the tumour necrosis factor (TNF)/TNF receptor R superfamily.

This is a personal account of how tumour necrosis factor (TNF) the prototype of a group of host-origin mediators, often known as pro-inflammatory cytokines, came into parasitology, and was subsequently realised to be central to the pathogenesis of most disease pathology. This contribution summarizes an example of how a curiosity-driven outsider, with initially no intention of heading this way, and no relevant experience, and with no more than the simplest of plans but an ambition to read as widely as it takes, and (most importantly) allowed to follow his head, can be what is required to give fresh insight into understanding a disease. It also gives the author's views on aspects of how the field of malaria disease pathogenesis seems to be developing. The hope is to inspire another generation to follow a similarly original course.

General nutritional effects on female CFLP mice harbouring larval Taenia crassiceps were investigated using groups of mice fed ad libitum on purified diets containing 2%, 4%, 8% and 16% (w/w) protein respectively. When uninfected and infected mice were compared over an experimental period of 20 weeks, it was established that a significantly higher proportion of uninfected mice survived the course of the experiment than infected mice. There was no evidence of the presence of the parasites having any effect on the overall food intake of the mice. Infected mice, however, were found to be significantly heavier, on a fresh weight basis, than their uninfected partners, but the pattern was reversed when the dry weights of mouse carcasses were compared following the removal of parasites. In general, more parasite tissue was recovered from mice feeding on the higher protein diets (8% and 16%).

Phase-interference microscopic examination of the infective, post-infective 3rd-stage and 4th-stage larvae of Dirofilaria immitis has identified a single cell body in each of the paired lateral amphidial nerves which undergoes characteristic morphological change during the development from 3rd- to 4th-stage larvae. Acetaldehyde—fuchsin staining of worm sections revealed fuchsinophilic material in the precise location of the amphidial nerve-cell bodies observed by phaseinterference microscopy. This material was found in 70% of infective larvae recovered from mosquitoes and in 100% of larvae recovered from micropore chambers 24 h after implantation into BALB/C mice. In pre-moult larvae recovered at 42 h (Experiment 1) and at 48 h (Experiment 2) fuchsinophilic material was demonstrable, but no staining was observed in those larvae in which separation of the 3rd- and 4th-stage cuticles had occurred. No such material was observed in 4thstage larvae recovered from chambers after 74 h, and in these larvae the amphidial nerve-cell bodies were not discernible. These cytological observations are consistent with a cycle of elaboration and release of neurosecretion associated with moulting in D. immitis.

The coccidium of mice (Mus musculus) was discovered by Eimer (1870) who named it Eimeria falciformis. It is round or oval. According to Reichenow the round oocysts measure 13·5–15μ and according to Reimer (1923) 14–18·9μ The oval oocysts measure 13–14×8–9μ or 16–21×11–17μ A residual body may, or may not, be present in the oocysts, but is present in the sporocysts. There is no polar granule in the oocyst.

Ancylostoma tubaeforme infective larvae have been tracked in agar and the dominant features of their tracks subjected to a numerical analysis. Very few of the features are uniformly random, most follow a well described normally random frequncy distribution. The mean size of an ‘are’ was 3·61 mm in radius and subtended an angle of 123° at the centre. The length of track per unit time declined with larval age and reversals were the main features to disrupt the pattern of tracks.