Each year the study of Diptera reveals some new and often unexpected facts concerning the mode of life of their early stages. The rich entomological literature dealing with this subject clearly shows that the diversity of conditions under which the larvae of this order of insects live surpasses that of any other order of the Animal Kingdom.

The present paper deals with descriptions of some new species of parasitic mites, a fresh study of the forms of Eulaelaps stabularis (Koch), some observations on the occurrence of hypopial forms on other parasitic arthropods, and finally some observations on Radford's ‘Genera and species of parasitic mites’ (1943).

A survey of tick activity curve data for Britain shows:

There are usually two peaks of female activity per annum, one peak in ‘spring’ and a lesser one in ‘autumn’, the date limits of the ‘seasons’ being slightly elastic. For a greater or lesser period in summer female-tick activity is low or practically absent, while in winter it is practically absent.

There are exceptions to the biannual type of female activity. In three areas, only one annual peak occurs. At Hethpool, north-eastern Northumberland, and in Ettrick Valley, southern Scotland, this single peak is in April–May; in the Hill o'Fare area, north-eastern Scotland, it is in July.

The theory of temperature control of activity (the limits being the range 45–60° F. average weekly maximum shade temperature, i.e. corresponding to spring and autumn conditions in Britain) does not stand up to the following facts: At Hethpool, following a spring female activity confined to the range 45–60° F., there was no autumn recrudescence when temperatures again passed through the same range. About half the annual female activity at Crag, south-western Cumberland, and practically all in the Hill o'Fare area occurred at temperatures of 60–70° F. and 60–65° F. respectively.

Solar radiation, evaporativity and humidity, as well as temperatures, of the macro-climate were investigated in relation to female activity. The tentative conclusion is that the duration of humidity level during daylight, in conjunction with temperature, may partly decide the amount and extent of activity in summer.

In spring, where spring activity obtains, males and females appear in small numbers a few weeks before nymphs. The bulk of male, female and nymphal spring activity, however, is concurrent, the curves having peaks at approximately the same date.

Again, where spring activity obtains, spring larval activity commences later than that of males, females and nymphs, the peak being about 1 month later.

Theories of seasonal activity are discussed.

1. A study has been made of the adult female Sarcoptes scabiei de Geer var. hominis (Hering). The findings have been compared to the description of Sarcoptes of the horse given by Buxton.

2. Forty-two living adult female S. scabici de Geer var. hominis (Hering) have been measured.

3. The apparent increase in size due to mounting is demonstrated.

4. The anatomy of the birth passage is discussed with special reference to the absence, in the specimens examined, of a genital operculum.

The following is a summary of our studies on population of head lice, adults and nits.

1. Out of a total of 8702 adult lice, the male population comprised 2031. The gross infestation rate per head was 129.9 and the maximum number found on a single head was 1434. A disproportion in the distribution of the two sexes was a marked feature.

2. Patients below the age of 11 showed a lower infestation rate than those above this age, and short-haired individuals were more heavily infested than long-haired ones.

3. Frequent combing of the hair and the use of oil did not seem to dislodge the adults or to prevent the females from laying eggs.

4. The maximum larval count on a single head was found to be 4260, the average number of larvae per single head was 418·8, and 9 to 1 was the maximum proportion of larvae to females.

5. The maximum number of nits on a single hair was found to be 17 and 5·06 was calculated as the average number per hair.

6. Treatment with kerosene and pyrethrum killed all the lice and nits, and reinfestation did not occur.

7. The infestation did not spread to healthy patients in the hospital ward; it is thought that the poor migratory habits of lice are responsible for this.

8. From studies on the reinfestation of an individual after treatment it is concluded that head-lice cannot establish themselves on any part of the body except the head, and if their access to the head is prevented, the lice will not survive for more than 24 hr.

In three experiments, the chief hosts, sheep, were withheld from a grazing until 0–3 weeks after the normal spring peak of female tick activity. This did not give rise to any appreciable prolongation of female tick activity into the normal summer offseason. More than half the female ticks actually available during the entire spring season were unfed when activity came to an end. This was due to the withholding of hosts. Hence that aspect of the ‘two-brood’ theory which claims that activity ends in spring, because all the available ticks are fed, is untenable as the complete explanation of bimodal annual activity.

Increase in sheep-stocking density, over the normal for a grazing, lowers the average infestation per sheep for that season at least.

The experimental data suggests the following:

(i) Delay in stocking a grazing with sheep results in a slightly higher-than-normal population of active female ticks which is fairly quickly absorbed after reintroduction of sheep.

(ii) A varying proportion of the tick population becomes active each week throughout the tick season, increasing up to the peak and decreasing thereafter.

(iii) The average duration of individual activity in a natural population of female ticks is probably not more than 1 month, perhaps less.

Practical applications of the findings to hill sheep farming are indicated.

1. The spores of Eimeria (not the oocysts) are the real infective agents and, as in other Sporozoa, they readily set free their sporozoites in the duodenum or in vitro under suitable conditions.

2. The protective oocyst has double walls: the ectocyst is thick and impervious to fluids but easily fractures by mechanical means, such as drying. Even though cracked, it may continue to protect the thin endocyst and spores until they reach the specially muscular regions of the alimentary canal. Free spores are probably also sometimes ingested.

3. The ectocyst is a continuous envelope without a persistent micropyle. It resembles keratin in many ways.

1. The effects of the following acids were studied: hydrochloric, nitric, sulphuric, formic, acetic, propionic, butyric, isovaleric, glycollic, lactic, oxalic, malonic, succinic, malic, tartaric, and citric.

2. The general effects of immersion in acid media include an increased stickiness of the cuticle in certain solutions, and the development of lateral bulges in the cuticle at the anterior region of the body, not necessarily in the same solutions. Movement gradually decreases, and death eventually occurs, often followed by swelling.

3. The survival times in various solutions were noted. Preliminary experiments showed that the logarithm of the survival time was approximately proportional to the logarithm of the normality of the acid. Later results showed great variability, and it was necessary to restrict the work to a single normality of each acid.

4. The toxicities of 0·206 N solutions of the sixteen acids were measured. These results showed that the mineral acids had markedly greater effects than the organic acids, and the importance of the former was further illustrated by using mixtures of HCl containing varying amounts of organic acids. The differences between the mineral acids may be explained by the lyotropic effects of the anions.

5. Equal normalities of organic acids were made up in a solution of HCl sufficiently strong to render the organic acids almost entirely undissociated. The relative toxicities of the mixtures were essentially the same as those of the dissociated acids.

6. The differences between the acids are thus partly due to the pH differences, and partly due to the dissimilar effects of the undissociated acids. The latter are believed to be due to a variety of causes, including molecular size, polarity of the molecule, and other factors as yet undecided.

Various records have, from time to time, been made of parasitic worms from marine fishes around the British Isles. Nicoll (1915) has compiled a very valuable list of the Trematoda, which class has received more attention than have the other parasitic worms of fishes. They have been recorded from Scottish waters by T. Scott (1901), from the Irish Sea by A. Scott (1904), from the Northumberland coast by Lebour (1908) and from Ireland by Bellingham in 1844 and Southern in 1912. The Cestoda have received less attention. Woodland (1927) has recorded some species from Plymouth, and a record of the trematode and cestode parasites of fishes from the Porcupine Bank, Irish Atlantic Slope, and Irish Sea has been made by Rees & Llewellyn (1941). The records of Nematoda and Acanthocephala are very scanty. Baylis & Jones (1933) include them together with trematodes and cestodes in a list of parasitic worms obtained from marine fishes at Plymouth.

The present paper includes two sections of a proposed series on the lungworms of the Odontoceti or toothed whales. Only members of the family Delphinidae among the Odontoceti have so far been reported as hosts to these lungworms.

The first section deals with the systematic relationships of the lungworms of the Odontoceti. They are held to constitute a family Pseudaliidae in the superfamily Metastrongyloidea. The nature of the female reproductive system and specifically of the ovejectoral apparatus in the suborder Strongylina is discussed and the concept expressed that the organization of the latter structure is of phylogenetic and taxonomic importance in this group. On the basis of variations in the ovejectoral apparatus three families of strongyline lungworms (except for Syngamus v. Siebold, 1836) are recognized—Dictyocaulidae Skriabin, 1941, Metastrongylidae Leiper, 1909, and Pseudaliidae Railliet, 1916.

The second section deals with the genus Halocercus Baylis & Daubney, 1925. Previous literature is reviewed. A key and table of measurements for the known species are presented. H. invaginatus (Quekett, 1841) Dougherty, 1943, is redescribed, and H. kirbyi n.sp. named and described.

During the handling of about 10,000 ticks in the course of insecticidal tests many abnormalities of the legs were encountered. Most of the cases were deficiencies due to the partial regeneration of a leg damaged in the previous nymphal stage. Two cases of special interest were not deficiencies, but exhibited supernumerary segments of leg.

1. Oviposition by L. sericata has been induced on a moist clipped fleece by incorporating ammonium carbonate and indole, hence attraction is not completely dependent on some factor produced by the living animal.

2. Chemistry of attractants. A new method for determining small amounts of hydrogen sulphide is described. Larval excreta contains hydrogen sulphide but no indole or skatole. Following incubation the ammonia and sulphydryl contents of various natural attractants are markedly increased.

3. Field trials on sheep. 0·002% ethyl mercaptan in conjunction with 0·1% ammonium carbonate was able to induce oviposition by L. sericata. The mercaptan concentration could be reduced to 0·001%, providing 0·0001% hydrogen sulphide was present. 0·01% mercaptan and aqueous solutions of hydrogen sulphide alone are not attractive.

4. The results obtained support the hypothesis that attraction is the result of the breakdown of cystine, with the production of sulphur compounds, coupled with the presence of ammonium carbonate (or of some putrefactive material).

5. Chemical baits. During the period 17 August–21 September 1943, various combinations of ammonium carbonate, hydrogen sulphide and indole in conjunction with sheep wool proved to be attractants for females of L. caesar.

1. A method for examining conditions governing anthelmintic activity in the small intestine is described. Nippostrongylus muris in the rat was the test organism and hexylresorcinol and C2C14 were the drugs examined.

2. The efficiency of hexylresorcinol was reduced by 50% in 1% sodium tauroglycocholate which reached a concentration of 1·3% in the rat small intestine. The adsorption of this drug on mucin reduced its concentration in intestinal fluids and prevented penetration to parasites under mucus. These inhibiting factors account for the inactivity of hexylresorcinol in the rat.

3. Tetrachlorethylene, which stimulated N. muris to leave mucus and enter fluids in the intestinal lumen, was not inhibited by bile salt and was found to act rapidly in the rat.

4. Sodium laurate activated hexylresorcinol more efficiently than sodium oleate at pH. 6·5. Both soaps showed intrinsic anthelmintic properties.

5. The results obtained in examining the rate of movement of fluids down the intestine and the effects of detergents, bile salts, mucin and ascorbic acid on drug activity are discussed.

A new genus, Kuhnia n.g., is created for the mazocraeidid monogenetic trematodes from the gills of mackerel. The type species, K. scombri (Kuhn), is redescribed (also K. minor (Goto), from the first specimens to be found outside Japanese waters), special attention being paid to the cuticularized parts, and the clamp skeleton is newly interpreted.

An alternation of sex phases has been found in Monogenea, which is well marked in K. scombri, resulting in changes in appearance which are described.

The comparison of heterauxesis curves constructed from the summarized data from six sets of dimensions shows that retardations in the rates of growth may be correlated with the onset of maximal reproductive activity, and accelerations with the relief from reproductive drain. Localized growth influence (similar shaped curves, with low post-larval coefficients of growth) has been found in the haptoral region, which is in marked contrast to the growth picture of the cuticularized oral suckers and the width of the body—the latter having both the highest and most variable growth coefficients between the six arbitrary length groups compared. Thus, neither absolute measurements nor ratios are, by themselves, of any value in specific diagnosis.

Graphical representation of allomorphosis for the genus Kuhnia affords a synoptic view of the changes brought about by the different types of differential growth of similar organs in each species throughout post-larval life. The dissimilar growth coefficients for certain dimensions are utilized in specific diagnosis. The relative diagnostic value of different entities is examined: the eggs of K. scombri are shown to be highly variable in size and shape.

The new facts obtained from the application of this metrical treatment, and its further application as a test for conspecificity of specimens outside the known size range, are discussed.

The systematics of the family Mazocraeidae are reviewed, and emended diagnoses of three species of Kuhnia are given in tabular form.

A re-examination of the haptoral sclerites forming the clamps, or ‘armoured suckers’, in Diclidophoroidea shows that they can be grouped into four main types, representing lines of evolution from what is here regarded as the primitive, or more generalized, form of clamp, that of the family Mazocraeidae. It has been shown that the form of the clamp skeleton must be regarded as of primary importance in the classification of the superfamily, since not only is it correlated with certain diagnostic characters of the soft parts of these worms, but it is usually fully developed some time before these parts make their appearance. Due attention has not always been paid to the detail of the clamps in systematic works, so that the position of some forms must remain uncertain until they can be redescribed. Owing to the sclerites often being twisted bars, curving through three dimensions, with the primary bars often jointed or fused, the appearance of different types of clamp is at first sight highly complex. The difficulty of interpreting them is increased by their being semi-transparent, and appearing of different shapes when viewed from various angles. These obscurities disappear when they are regarded as modifications of the fundamental plan found in Mazocraës and its allies.

1. The inactivation by γ-rays of tobacco mosaic virus is studied at various concentrations. It is found that the inactivation dose is independent of concentration at high concentrations, and at low concentrations also attains a constant, but lower, value. Over an intermediate range the inactivation dose increases with increase of concentration.

2. These facts are explained on the basis that when irradiated dry or in concentrated solution the inactivation is direct and due to ionization produced inside the virus particle. At lower concentrations the inactivation is largely indirect and due to ionization of the water.

3. Gelatin added to the solution protects the virus against the indirect action of radiation.

4. Curves are given of the inactivation of dry preparations of ribonuclease and adenylpyro-phosphatase (myosin) by X-rays.

5. It is shown that on the assumption that a single ionization in an enzyme molecule leads to its inactivation, measurement of the inactivation dose leads to a rough estimate of the molecular weight of the enzyme.

6. There appears to be no fundamental difference in the mechanism of radiation-inactivation of viruses and enzymes.

All irradiations were carried out at the Strangeways Laboratory. The virus was prepared and tested at the Plant Virus Station and the Molteno Institute. The enzymes were prepared and estimated at the Biochemical Laboratory. We are indebted to the British Empire Cancer Campaign for defraying the cost of the X-ray equipment at the Strangeways Laboratory.

Reasons are given for rejecting a recent proposal to change the names Anisakis simplex to Capsularia marina, Anisakis to Capsularia, Anisakinae to Capsulariinae and Porrocaecum decipiens to P. piscium. The question of the possibility of identifying the larval forms of Ascaridae occurring in fishes is discussed.

A new species of cephaline gregarine, Gregarina rhyparobiae n.sp., parasitic in the gut of a tropical cockroach Rhyparobiae maderae, from East Africa, is described.

The main features of the life-history of Mermis nigrescens, so far as it is known, are briefly discussed. Some data have been collected on its distribution in the British Isles, and on the seasonal appearance of the egg-laying females. The insect hosts of the worm are discussed, and feeding experiments on various invertebrates are recorded, including the experimental infection of the common earwig (Forflctila auricularia). This insect, which has also been found naturally infested, is regarded as an important host for the species, more especially where grasshoppers are absent. Observations by other workers on the influence of the number of larvae per host on the sex of the developing worms, and on the survival of the host, have been confirmed. Two new species, closely related to M. nigrescens, are described: M. kenyensis and M. tahitiensis, from Africa and Tahiti respectively.

1. Seven species of lungworms are so far known to occur in North American deer of the genus Odocoileus: Dictyocaulus filaria (Rudolphi, 1809) Railliet & Henry, 1907; D. viviparus (Bloch, 1782) Railliet & Henry, 1907; Varestrongylus alpenae (Dikmans, 1935) n.comb.; Pneumostrongylus tenuis n.sp.; Elaphostrongylus odocoilei Hobmaier & Hobmaier, 1934; Protostrongylus coburni Dikmans, 1935; and P. macrotis Dikmans, 1931. Specimens (from deer) of all these species except Dictyocaulus filaria and Protostrongylus coburni have been studied in the course of this work.

2. Two subspecies of Odocoileus virginianus (Boddaert) and two of O. hemionus (Rafinesque) have been reported as hosts for lungworms. These may be listed with their established lungworm parasites as follows:

Common white-tailed or Virginia deer, Odocoileus v. virginianus (Boddaert): Dictyocaulus viviparus, Varestrongylus alpenae—new record, Pneumostrongylus tenuis—new record.

Northern white-tailed deer, Odocoileus v. borealis Miller: Dictyocaulus filaria, D. viviparus, Varestrongylus alpenae, Protostrongylus coburni.

Rocky Mountain mule deer, Odocoileus h. hemionus (Rafinesque): Dictyocaulus viviparus, Protostrongylus macrotis.

Columbian black-tailed deer, Odocoileus h. columbianus (Richardson): Dictyocaulus filaria, D viviparus—new record, Elaphostrongylus odocoilei.

3. A new species, Pneumostrongylus tenuis, is based on a single male lungworm from a bronchiole of Odocoileus v. virginianus. Pneumostrongylus tenuis differs from P. calcaratus Mönnig, 1932, genotype of Pneumostrongylus Mönnig, 1932, in spicular, gubernacular, and bursal characters.

4. Pneumostrongylus alpenae Dikmans, 1935, is transferred to the genus Varestrongylus Bhalerao, 1932, as a result of the study of specimens of Pneumostrongylus alpenae and Varestrongylus pneumonicus Bhalerao, 1932, genotype of Varestrongylus. The former becomes Varestrongylus alpenae (Dikmans, 1935) n.comb. Also placed in this genus are Varestrongylus sagittatus (Mueller, 1890) n.comb. (syn. Strongylus, or Protostrongylus sagittatus) and Varestrongylus capreoli (Stroh & Schmid, 1938) n.comb. (syn. Protostrongylus capreoli).

5. The reports of Protostrongylus coburni from Odocoileus v. virginianus by Goble (1943) were based on larvae and adult lungworms in sections of lung tissue. Subsequent observations by Cheatum (in litt.) strongly indicate that these were actually Varestrongylus alpenae.

6. The structure of the gubernaculum in Protostrongylus macrotis is redescribed, and the conclusion reached that this form may be regarded as an aberrant species of Protostrongylus. Appendages at the distal ends of the gubernacular crura are given the name pedes (sing, pes), and the sclerotized are, found in the bursa of a number of genera of the Protostrongylinae, the name arcus.

7. The fact that crura have not been described for the gubernaculum of Elaphostrongylus cervi Cameron, 1931, genotype of Elaphostrongylus Cameron, 1931, whereas E. odocoilei Hobmaier & Hobmaier, 1934, possesses them must be regarded as a possibly significant difference between the two species; but it is suggested that E. cervi may be found to have these structures. Therefore E. odocoilei is left in Elaphostrongylus.