Original Articles
Plutella maculipennis, Curt., its natural and biological Control in England
- J. Eliot Hardy
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- 10 July 2009, pp. 343-372
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1. Plutella maculipennis, Curt., a widespread Lepidopterous pest of Brassica was introduced into New Zealand about sixty years ago. In most countries a high degree of natural control is maintained, but in New Zealand the moth population is permanently maintained at a high level. Investigation showed that in New Zealand there were no natural enemies of importance, while in other areas these are constantly associated with Plutella.
2. The distribution of the moth throughout the world is exceedingly wide, but in England it only occasionally reaches pest proportions.
3. Preliminary work indicated that two Campoplegines, Angitia cerophaga and A. fenestralis, constantly parasitized large numbers of the Plutella larvae. Initial efforts were devoted to collecting and breeding a large supply of these in England for introduction into New Zealand as controlling agents.
4. From several thousand specimens of Plutella, fourteen species of parasites were recovered, of which eight were hyperparasites. The only parasites which were numerically important were the two parasites, Angitia cerophaga and A. fenestralis. Their efficiency is not impaired to any appreciable extent by hyperparasites. A key showing the diagnostic differences of the parasites and hyperparasites of Plutella is given.
5. These two species of Angitia are commonly recorded as parasites of Plutella throughout the world, although under different names. A large quantity was bred in the laboratory and despatched to New Zealand after overcoming certain difficulties connected with transport. It appears that both species of parasite must overwinter in other hosts than Plutella.
6. Certain experiments were performed in an endeavour to assess some of the effects of climate. The upper limiting temperature of Plutella is approximately 40°C. and the lower limit for breeding purposes about 10°C. All stages of the moth can survive short periods of cold greater than 10°C., but it is believed that hibernation is normally accomplished in the adult stage. As the immature stages of the moth live in a specialised microclimate of high humidity, changes in the moisture content of the general atmosphere have little effect. Rain, if appearing at certain critical times in the life-cycle, may be a controlling agent.
7. The most favourable areas for multiplication of the moth appear to be in the sub-tropics and warmer temperate zones. It is suggested that Plutella originated in the Mediteranean region.
8. Even in the cooler temperate countries the climate would allow an indefinite increase in the moth. It is believed that an effective check on this multiplication is supplied by parasites.
9. As the climate of England and New Zealand are essentially similar there is reason to suppose that the introduction of parasites from the former country will lead to eventual control being obtained in New Zealand.
The Selection of a Standard Insect for the Laboratory Testing of Insecticides
- H. J. Craufurd-Benson
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- 10 July 2009, pp. 119-123
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1. The standards adopted by the author for a test insect suitable for the laboratory testing of insecticides are given.
2. The inadvisability of using insects collected in the field, or insects that do not breed naturally throughout the year, is illustrated.
3. The results of a search amongst stored-product insects, involving the testing of 27 different species, are given.
4. Ahasverus advena, Oryzaephilus surinamensis and Oryzaephilus mercator have been found to be suitable laboratory test insects.
New injurious Curculionidae (Col.)
- Guy A. K. Marshall
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- 10 July 2009, pp. 1-8
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Head continuous with the rostrum, not constricted behind the eyes, which are moderately convex, the forehead as broad as the base of the rostrum. Rostrum narrowing from the base to the antennae ; mandibles squamose, mentum bare. Antennae with the scape exceeding the hind margin of the eye, the distal joints of the funicle elongate, joint 2 longer than 1. Prothorax with the base depressed, at a lower level than the apical margin, sinuate or bisinuate. Elytra obovate, widest behind the middle, with or without shoulders. Legs with only the front femora armed with a small sharp tooth ; front tibiae only finely denticulate and with the dorsal edge curved, hind tibiae with the corbels enclosed and not ascending the dorsal margin ; joint 2 of hind tarsi not transverse ; front coxae nearer to anterior margin of prosternum ; claws free. Sternum with the metasternum not longer than a median coxa. Venter with the intercoxal process about as wide as a hind coxa.
Experimental Studies in Insect Parasitism. VI.—Host Suitability
- George Salt
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- 10 July 2009, pp. 223-246
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1. For the purposes of this paper a suitable host is defined as one on which the parasitoid can generally reproduce fertile offspring.
2. To be suitable for Trichogramma, a host must satisfy conditions required by two generations of the parasite: it must be such that it can be actually parasitized by the adult parasitoid; and it must provide an environment in which the parasite offspring can develop.
3. Some hosts prevent the attack of Trichogramma leading to parasitization by the physical resistance of their chorion; others by inhibiting the impulse to oviposition.
4. Five physical characteristics of the hosts of Trichogramma are investigated: the permeability, rigidity, and hardness of the egg-shell; and the fluidity and quantity of the egg-contents (pp. 226 to 231).
5. Eggs of Sialis lutaria, Tenebrio molitor, and Bruchus obtectus are chemically unsuitable for Trichogramma evanescens as food.
6. Two biological characteristics of the host, its viability and its age, do not directly affect its suitability for Trichogramma; a third, the ability of the embryo to move, is of some importance.
7. The various known factors of host unsuitability are given in tabular form (p. 239).
8. In spite of numerous attempts during several years it has not been possible to develop a strain of Trichogramma evanescens which could use Bruchus obtectus as a host.
9. The host list of most groups of parasites is greatly limited by the inaccessibility of many species; it is further restricted in some groups (e.g., the parasitoid Hymenoptera) by the selection exercised by the parasite; it is finally limited in all groups (and especially the parasitoid Diptera) by the unsuitability of many infected animals.
10. The division of the problem of host specificity into the three parts, host finding, host selection, and host suitability, is fundamental.
Three new Moths (Agrotidae, Pyralidae) of Economic Importance
- W. H. T. Tams
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- 10 July 2009, pp. 9-10
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The material here described has been received by the Imperial Institute of Entomology, and I am indebted to Sir Guy Marshall for the opportunity of studying it. The types have been presented to the British Museum (Natural History).
A new Species of Apanteles (Hym. Brac.) bred from Carposina adreptella attacking Raspberry in New Zealand
- D. S. Wilkinson
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- 10 July 2009, pp. 247-249
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Apanteles carposinae, sp. n.
♀. Black; the front legs entirely (save for the black feet and for some occasional slight darkening on femora above and below, on tibiae above, and on coxae and tarsi), middle legs entirely (save for the black feet and for femora darkened above and below and for some occasional slight darkening on tibiae and coxae), hind coxae at apex below, hind trochanters and trochantines, hind femora (save above and below extensively), hind tibiae, hind tarsi (save for black feet and some darkening), and palpi, red testaceous; tibial spurs pale; wings infumated evenly throughout and the setae coloured; stigma, metacarp, and all veins, brown; stigma uniformly opaque.
♂. Black; front coxae (save at base), front trochanters and trochantines, front femora (save for darkening above and below, which is sometimes strong), front tibiae (save for strong darkening above), front tarsi (save for some darkening and the black feet), middle coxae (save at base or even basal half), middle trochanters and trochantines largely, middle femora (save for extensive strong darkening above and below), hind coxae at apex below to some extent in the lighter but not in the darker examples, hind femora (save for extensive strong darkening above and below), and palpi, red testaceous; the four posterior tibiae and tarsi, and the hind trochanters and trochantines, largely darkened throughout save perhaps in an occasional lighter example; tibial spurs pale; wings infumated evenly throughout and the setae coloured; stigma, metacarp, and all veins, brown; stigma uniformly opaque.
The Reactions of Mosquitoes to Temperature and Humidity
- R. C. Muirhead Thomson
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- 10 July 2009, pp. 125-140
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Reactions to Temperature
1. The reactions of Culex fatigans to temperature were studied by means of a new type of temperature gradient apparatus based on the same principle as the humidity alternative chamber.
2. Females at different stages were exposed to a range of 5°C. at different parts of the temperature scale, and it was found that the sensitivity was very much greater at high temperatures than at low ones.
3. The most striking feature of behaviour at all stages was the strong avoidance of high temperatures. This was strongest in the hungry females, less strong in the blood-fed females and those with mature ovaries, and least strong in the newly emerged females.
4. Newly emerged females showed avoidance of high temperature below 30°C., but not below 25°C. They also showed a weak avoidance of low temperature. At 29°C. they were sensitive to a difference of 1°C. or a gradient of 0·05°C. per cm.
5. Hungry females showed a strong avoidance of high temperature below 25°C., the reaction still taking place below 15°C. There was no avoidance of low temperatures.
6. Blood-fed females and those with mature ovaries showed a strong avoidance of high temperatures below 25°C., but below 20°C. they were unaffected by temperature differences. Blood-fed females were sensitive to a difference of 1°C. or a gradient of 0·05°C. per cm. at 23°C.
7. Except in the case of newly emerged females there was quite a close relation between the reactions to temperature and the effects of temperature.
8. Reasons are given for regarding the temperature reactions of Culex as of first importance in determining the behaviour of the mosquitoes when seeking a resting place.
Reactions to Humidity
9. The reactions of Culex fatigans to humidity were studied by means of the alternative chamber, in a dark constant temperature room at 25°C.
10. At all stages the strongest humidity reaction was an avoidance of high humidities above 95 per cent. R.H.
11. This reaction was strongest in the blood-fed females and those with mature ovaries, less strong in the newly emerged females, and weakest in the hungry females.
12. The avoidance of high humidity was strongest when there was a difference of 20 per cent. R.H., such as a 78–98 per cent. R.H. gradient. Near saturation point all stages except hungry females were sensitive to a difference of 1 per cent. R.H. or a gradient of ·05 per cent. R.H. per cm. Hungry females at this point were not sensitive to a difference of less than 3 per cent. R.H.
13. All stages showed a slight but regular avoidance of low humidities, provided a sufficiently large humidity range, not less than 40 per cent. R.H., was present.
14. Hungry females, despite the onset of mortality due to desiccation, showed no sharp avoidance of low humidities which were rapidly fatal to them.
15. Between 30 and 85 per cent. R.H. all stages were unaffected by humidity differences of as much as 40 per cent. R.H.
16. The avoidance of high humidities was equally strong in blood-fed females at 20, 25, and 30°C. At 35°C., greatly increased activity eliminated the reaction.
17. The reaction was much less intense in daylight and disappeared altogether after sundown.
18. Reasons are given for considering that the measure of humidity which determines the behaviour of the mosquito is relative humidity and not saturation deficiency, even though the latter is the important one in the water relations of insects.
Notes on the Insect Enemies of Chermes with particular Reference to Pineus pini, Koch, and P. strobi, Hartig
- Frank Wilson
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- 10 July 2009, pp. 373-389
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Pineus pini has been introduced by accident into Australia and has become a pest of some importance on Pinus radiata and P. pinaster and also attacks a few other species.
The Mosquitos of the Island of Corfu, Greece
- Theodore Stephanides
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- 10 July 2009, p. 251
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The following mosquitos should be added to the list given in my earlier paper on this subject (Bull. Ent. Res. 28, 1937, pp. 405—407).
1. Anopheles elutus, Edwards.
The larvae are found in the same habitats as those of A. maculipennis, but seem to show a greater preference for waters near the sea-shore. A. elutus appears to be considerably rarer in Corfu than A. maculipennis, but sufficient data are not yet to hand to settle this question.
2. Anopheles plumbeus, Stephens.
Not common. I have obtained the larvae from the rot-holes of oak, elm and white poplar, but never so far from those of olive-trees. They favour deep holes containing plenty of rotting material.
3. Aëdes (Ochlerotatus) caspius, Pallas.
The larvae are sometimes present in fresh, but more frequently in slightly brackish waters. They are often gregarious with the larvae of O. detritus, Hal., but are much less abundant than the latter.
4. Aëdes (Ochlerotatus) pulchritarsis, Rondani.
The larvae live in rot-holes of oak, elm and white poplar, and are sometimes met with in considerable numbers in the same hole. They prefer holes in which the collected water has become thick and very dark amber in colour owing to the presence of decaying wood debris.
5. Orthopodomyia pulchripalpis, Rondani.
The larvae are found in the same habitats as those of O. pulchritarsis and are often gregarious with the latter. They are less plentiful, on the whole, than O. pulchritarsis and prefer somewhat clearer water.
Note.—In my paper referred to above I mentioned that Finlaya echinus, Edw., is commoner in Corfu than F. geniculatus, Oliv. This statement is due to an error of determination arising from the fact that in many of the Corfu larvae of F. geniculatus the bristles of the abdominal tufts are somewhat more developed than those described in some text-books.
Problems concerning the Efficiency of Oils as Mosquito Larvicides.—Part I. The Stability of Oil Films on the Surface of Water
- David R. P. Murray
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- 10 July 2009, pp. 11-35
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Films of oil which have originally covered the whole of the surface of an area of water frequently break up and leave the oil only in patches, and the rest of the surface uncovered. An investigation has revealed that this may be the result of either or both of two circumstances.
It has been shown that instability may result from :—
I. Certain relationships between the volatility of the aromatic and aliphatic hydrocarbons composing the oil mixture.
II. The presence of certain polar substances dissolved in the oil.
I. The volatility relationships which determine the stability or instability are as follows :—
(a) If the aromatic hydrocarbons are more volatile than the aliphatic, a tendency exists for the oil to become concentrated into one central thick lens with the rest of the surface uncovered by oil.
(b) If the whole of the aromatics are more volatile than the whole of the aliphatics, this action is very rapid and occurs whatever the proportion of the mixture.
(c) If the difference in the volatility is only small, the phenomenon is only observed when the proportion of aromatics to aliphatics is very near to unity.
(d) If the boiling range of the aromatics overlaps the boiling range of the aliphatics (as occurs when two oils containing both types of constituents are mixed), the phenomenon is much less clearly defined.
(e) Olefinic oils, e.g., oils obtained by cracking, behave like aliphatic oils in so far as this behaviour is concerned.
It is believed that these changes would not occur if the oil was extremely pure, since lenses are only stable if subject to lateral pressure from an invisible film of contaminating material.
II.—The effect of polar materials can be summarised:—
(a) Solutions of certain organic substances in oil tend to make unstable films on the surface of water; rupture of such a film (by wind or other agitation) allows a unimolecular film of the added substance to spread at the air-water interface. This forces back the oil film. The greater the agitation the less the area of surface eventually covered by oil. In this class of substances are fats, fatty acids, naphthenic acid (a natural constituent of petroleum), some sulphonic acids and cholesterol.
(b) Certain other substances act in a contrary manner. They do not promote instability but actually counteract and, if present in sufficient proportion, overcome the instability produced by the first type of substance. The substances falling in this group are all at present of unknown composition, but include “ cracked spirit gum ” (a material derived by polymerisation of olefinic hydrocarbons), certain resins, and some substance present in petroleum and remaining in the residue after distillation. The last of these acts as a natural “ stabiliser ” and masks the instability phenomenon to some extent in commercial oils. It is found in largest quantity in the undistilled residue of aromatic concentrates.
(c) The quantitative relationship between the “ stabiliser ” and the substances promoting instability is not linear. Successive increments of “ stabiliser ” equalise larger and larger amounts of the other.
(d) Long-chain molecules such as fatty acids are the most difficult to overcome by “ stabiliser.” Naphthenic acid is more easily counteracted, cholesterol still more easily.
The following recommendations can therefore be made as to the desirable composition of anti-malarial mixtures, so far as film stability is concerned :—
1. The oil should contain either a small aromatic content or a very high one ; it should not contain 50 per cent. aromatics unless they are very high-boiling (e.g., of lubricating base fraction).
2. It should consist of a mixture of wide and overlapping cuts of oil.
3. It should not contain fats or fatty acids added as spread-aiders. If spread-aiders are desired, resins should be employed.
This research was financed in its entirety by a grant contributed equally by the Anglo-Iranian Oil Company, the Asiatic Petroleum Company, and the Burmah Oil Company. To the research chemical staffs of these companies I express my thanks for samples of oil and for much technical information and advice. My thanks are also due to Professor P. A. Buxton and Professor N. K. Adam for advice and help.
A Method for investigating Membrane Permeability
- S. T. P. Brightwell
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- 10 July 2009, pp. 391-403
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Recent developments of physiology have emphasised the importance of membranes, and in entomology, studies on the permeability of membranes would offer the necessary basis for investigations on the physiological action of insecticides, particularly those applied externally, as well as on the many aspects of insect physiology.
Descriptions of some African Eulophidae (Hym. Chalc.)
- Ch. Ferrière
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- 10 July 2009, pp. 141-147
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The family of the Eulophidae, which is probably the largest family of the Chalcidoidea, is still very little known, both systematically and biologically. Being small, they are often bred in large numbers from a single host and are thus of great economic importance, but not always useful, as many species are hyperparasites. The study of the African Eulophidae is still at its beginning, since only about 60 species are known, two-thirds of which have been described by Waterston and Silvestri. The Imperial Institute of Entomology has received and is receiving many species which still remain unnamed. Most of them belong to large genera, like Euplectrus, Pleurotropis, or Tetrastichus, which should be studied monographically. The six species described below have been chosen partly for their possible economic importance, partly because they are represented by series of males and females.
On the Protection of Sheep from Maggot-fly
- J. MacLeod
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- 10 July 2009, pp. 149-163
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Research on the control of maggot-fly on sheep has in the past been seriously handicapped by the uncertainty of natural incidence of strike ; many experiments have been rendered invalid by the failure of the controls to react, the absence of controls, or by reason of the fact that the incidence of strike was so low as to make differences between comparative groups of no significance. For these reasons much of the published evidence does not bear critical examination.
There are now available, however, critical methods for the estimation of the protective value of dips and sprays, and it is essential, if further progress in maggot-fly control is to be made, that use be made of these methods for the accurate assessment of the larvicidal and repellent properties of experimental dressings, and for the duration of effect of these properties. A continuation of the present tendency to general statements that such and such substances were found to protect sheep for so long, without specification of what precisely the sheep were being protected against, and especially when unaccompanied by detailed protocols which will.allow the reader to exercise an independent judgment of the reliability of the results, will only lead to further discordance in a subject already suffering from a lack of uniformity in the standards of different workers, and the absence, even, of any precise definition of much of the technical jargon associated with it.
In the first part of this paper the nature and potentialities of the three possible functions of a maggot-fly dip or spray have been outlined, and the appropriate terms defined. It has been pointed out that field tests, for which it is difficult and sometimes impossible to furnish logically acceptable control data, are unreliable and may be definitely misleading ; at best they still leave the investigator uncertain as to which function of the dressing is responsible for the protection conferred, and consequently handicapped in his efforts to improve still further the protective value of the preparation under test.
In dealing with the maggot-fly problem, two principal lines of attack are possible ; the fly may be prevented from laying its eggs, or alternatively, the fleece may be so impregnated with toxic chemicals that the eggs, or any larvae which succeed in hatching from these, are killed. If a completely reliable repellent were available, no larvicide would be necessary ; conversely, if a thoroughly effective larvicide were available, a repellent would be not only unnecessary but also undesirable, for the more eggs which the flies could be induced to lay on sheep the better.
A third possible line of attack is the use of an antiseptic, which neutralises the bacterial activity in the fleece, and so ends the attraction of the sheep for the gravid female fly. Since, however, such neutralisation is so easily overcome by accidental fouling of the fleece, scouring or other cause, it is obviously unsafe to rely on this negative virtue alone for immunity from attack. The overcoming of the antiseptic property is the chief reason why carbolic dips, which rely on their antiseptic value, tend to have no effect, or even to have a harmful effect, after the dipping solution begins to get fouled by urine and faecal matter. With larvicidal dips, this fouling is of much less consequence, for the active protection conferred by the toxic chemicals prevents the blows which result from any such fortuitous “ attractivation ” from developing to strike.
With regard to the two principal lines of attack mentioned above, it may be stated here that prolonged and thorough tests have failed so far to reveal any substance possessing a reliable repellent action, which remains completely reliable for more than a few days. In all the commonly used repellents tested, the protection was found to be uncertain and seldom of a high degree, It appears, therefore, that we have yet to find the ideal repellent, and until such time it is obviously safer to rely on larvicidal protection.
It is equally obvious that, to ensure thorough penetration of the larvicide, it must be applied by actual immersion of the sheep. Spraying, though the ideal method for applying a repellent, cannot be regarded as suitable in the case of a larvicide, since it coats only the outer part of the wool staple with the spray fluid, and does not thoroughly saturate the fleece down to the skin surface.
With regard to the experimental evidence given in detail in the present paper, the results may be held to suggest the following conclusions:—
1. Carbolic dips neither repel the adult fly nor prevent larvae from establishing active strike on the skin.
2. Cresylic acid, incorporated in a mineral oil base, is not effective as a spray or as a dip in protecting susceptible sheep or preventing development of strike from blow.
3. Arsenic remains in the fleece, and continues to exercise a protective effect against development of strike for some weeks after application. This protection may be only partial (Table III) or almost complete (Table II, IV and VII) ; under winter conditions it lasts for about four weeks, and in the case of one form of soluble arsenic at least, it has been shown to be only slightly affected by heavy rain.
Neue Indo-Australische Tachinidae
- Von N. Baranov
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- 10 July 2009, pp. 405-414
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Die folgenden Beschreibungen beziehen sich auf die Tachiniden (s. 1.), welche ich vom Imperial Institute of Entomology in London zum Bestimmen erhielt. Für die Zusendung dieses sehr wertvollen und schönen Materials möchte ich auch an dieser Stelle dem Herrn Direktor Sir Guy A. K. Marshall meinen Dank aussprechen.
On the Ecology of the Citrus Red Spiders in Palestine
- H. Z. Klein
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- 10 July 2009, pp. 37-40
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On the basis of ecological data, breeding experiments, and activity trials, the two species of red spiders (Anychus orientalis, Zacher and Epitetranychus althaeae, Hanst.) found in Palestine are differentiated. The reason for the different distribution of the two species throughout the world is explained. The common red species is found to be a cosmopolitan, the Oriental red spider a subtropical element.
Physiological Conditions of Cold-hardiness in Insects
- I. W. Kozhantshikov
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- 10 July 2009, pp. 253-262
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The results of the present investigation can be summarized as follows:—
1. Cold-hardiness in insects depends on the physiological state of the organism; the most resistant are the phases in diapause (prepupae of Croesus septentrionalis, eggs of Lymantria dispar, pupae of Acronyctinae); not so hardy are the caterpillars of Lasiocampa quercus stopped in their development and prepupae of Agrotis segetum; practically non cold-hardy are developing (or growing) insects, viz., the full-grown larvae of Calliphora erythrocephala, the growing caterpillars of Loxostege sticticalis and Agrotis segetum.
2. The difference in the cold-hardiness of these three groups depends on the specificity of their cellular respiration. Growing insects show in their cellular respiration the prevalence of oxydases, the activity of which is connected with characteristics of their cellular structures; in cold-hardy insects the cellular respiration is closely connected with the anoxybiotic processes caused by the dehydrases; their activity is not bound up with the structural elements of the cells, but is closely connected with the presence of non-saturated fat-acids (Dixon, 1929; Meldrum, 1934) peculiar to insect fats.
3. The respiration of growing or developing insects is entirely and rapidly destroyed by narcotics, cyanide and low temperatures; the effect of these agents is due to the destruction of the cellular structures. The respiration of cold-hardy insects is characterised by its definite thermostable part and is also resistant to narcotics (or cyanide, Bodine, 1934). Destroying the cellular structures does not affect that respiration. Cold-hardiness increases with the increase of the percentage of thermostable respiration.
4. Freezing of the protoplasmic water causes the death of an insect only in the absence of thermostable respiration. Many insects in diapause (characterised by a high percentage of thermostable respiration) can be frozen without any lethal effect (Pyrausta nubilalis, Croesus septentrionalis, Lasiocampa quercus). It is clear that the freezing of the free protoplasmic water cannot be considered as an obligatory cause of “ anabiosis.”
5. The quantity of fat does not show any direct connection with thermostable respiration and cold-hardiness in insects. It is probable that the important factor is the quality of the fats, namely, the rôle of non-saturated fat-acids. The increase of cold-hardiness in insects after dehydration can be connected with the changes in cellular respiration; the same can be said regarding the general connection of the water content of the protoplasm and cold-hardiness.
An improved Method for testing Liquid Contact Insecticides in the Laboratory
- H. J. Craufurd-Benson
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- 10 July 2009, pp. 41-56
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1. Methods for laboratory testing of contact insecticides are reviewed, and some of the disadvantages of these methods are discussed. Reasons are given for preferring an immersion to a spraying method, and the necessity for a supply of “ standardised ” insects is stressed.
2. An improved immersion method for laboratory testing of contact insecticides is described, and the rigid technique necessary is detailed.
3. The effect on the resistance of Ahasverus advena to a derris insecticide of varying the time of immersion, the age of the insects, the temperature and the humidity before, during, and after immersion is illustrated and shows the necessity of controlling all these factors.
4. Results with a standard derris insecticide are given to show the great accuracy that can be obtained by the new method ; that the same result with the same insecticide can be repeated from day to day; and that two workers using the same insecticide have obtained identical results.
5. The reaction to starvation is correlated with variations in age, temperature, and humidity, to show that the starvation death rate is a measure of the insects' powers of resistance to an insecticide.
6. Statistical analysis and discussion of methods of expressing mortality is reserved for a later communication.
The Life-history and Growth of the Cockroach Blatta orientalis, Linn.
- M. A. H. Qadri
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- 10 July 2009, pp. 263-276
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The life-history of Blatta orientalis has been studied from the time of the deposition of the ootheca by the female till the nymphs of the third generation emerge, viz., through two embryonic and one post-embryonic lives.
The cockroach passes through one pronymphal and six nymphal stages and moults seven times after its exit from the ootheca.
The post-embryonic growth, including the increase of the antennal and cercal joints, and the modification of the external genitalia, is described. It has been shown that nymphs of various instars and their sexes can be distinguished, especially with the help of the genitalia, the number of cercal joints, and the growth of the wing-rudiments.
The average time taken by 27 nymphs to mature at 27·5C. is 279 days. The males mature earlier than the females and also die before the latter.
The formation and structure of the spermatophore are described and also the exact mode of copulation, including the use of various parts of the male genitalia.
The ootheca is deposited with special care by the female in that she digs a pit with the help of her mandibles and the fore legs and covers the ootheca afterwards. The nymphs emerge without the help of the female and the latter does not take any care of the ootheca after it has been safely deposited.
Notes on the Taxonomy and Synonymy of Zele, Curtis, and Macrocentrus, Curtis (Hym., Braconidae)
- G. E. J. Nixon
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- 10 July 2009, pp. 415-424
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This paper is the outcome of an attempt to identify certain species of Braconidae received from the Forest Research Institute, Dehra Dun. The material comprises parasites of various Lepidopterous pests defoliating teak, shisham and deodar. Three of them are dealt with in the following pages ; the others will be discussed in a later paper.
On African Sandflies.—III
- Oskar Theodor
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- 10 July 2009, pp. 165-173
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The following paper deals with collections of sandflies made by Professor P. A. Buxton in Nigeria, and by the late Professor J. G. Thomson in Nyasaland, and collections sent by Sir Guy Marshall, Director of the Imperial Institute of Entomology, and by Dr. F. W. Edwards of the British Museum (Nat. Hist.), for identification.