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.

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 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.

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.

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.

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.

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.

It has been shown that Atropa belladonna acts as a symptomless carrier of Hyosoyamus Virus I. Some symptoms caused by this virus on other solanaceous plants are described.

A naturally occurring virus complex in Hyoscyamus niger was found to consist of Solanum Virus I (potato virus X) and Brassica Virus I. During the course of the investigation it was found that potato virus X forms local lesions on the cotyledons of ridge cucumber without systemic infection and that Brassica Virus I behaves similarly on the inoculated leaves of Nicotiana sylvestris.

1. The composition of the perienteric fluid of Ascaris lumbricoides of the pig, immediately after removal from the host and after varying periods of in vitro starvation, is recorded.

2. Apart from the more frequently observed constituents of invertebrate tissue fluids, the body fluid of Ascaris was found to contain ascorbic acid, amino sugar and small amounts of uronic acid.

3. Large amounts of anion other than chloride, probably fatty acid, must have been present in the body fluid, though chloride was probably the predominant anion in fluids of parasites which had passed several days of in vitro life.

4. The chief factors (starvation, osmotic pressure and the nature of the medium, etc.) affecting the composition of the body fluid are briefly discussed.