During recent years in Sweden much time and work has been devoted to the devising of accurate and withal time-saving methods of estimating the number of bark-beetles breeding in a trunk as well as the total number of bark-beetles per hectare in a given instance. The results achieved by the methods finally adopted seem to us so satisfactory that we venture to think that the methods in question may be used to advantage even in other countries, when similar problems arise.

Milionia isodoxa Prout is a serious defoliator of planted hoop pine, Araucaria cunninghamii, in the Highlands of Papua New Guinea. The insect has been found in seven mainland districts, and larvae have been collected from naturally occurring hoop pine in the Madang and Southern Highlands Districts. M. isodoxa is multivoltine, the life-cycle taking approximately eight weeks. The durations of the five larval instars are 4, 4, 4, 5 and 10 days, respectively, and of the pupal period approximately two weeks. The males feed primarily on organic solutes, the females on nectar, so that the sex ratio of adult M. isodoxa in the hoop pine plantations at Bulolo varies with the time of day and locality. Pupae may be attacked by two species of Ichneumonidae and one of Braconidae, and the ants Anoplolepis longipes (Jerd.) and Oecophylla smaragdina (F.) are particularly effective larval predators in the Bulolo plantations; some adults are killed by spiders. The fungus Beauveria bassiana is responsible for high pupal mortality in the Highlands. Frass-drop frequency studies of M. isodoxa larvae in the laboratory showed that feeding activity is greatest in the early instars, and is greater at night for all instars. Larvae reared at 21°C required 14 days more for development than did those reared under the normal daily fluctuation, 19–31°C.

Plant-derived compounds can be an environmentally friendly alternative to synthetic pesticide use for pest management. Essential oils (EOs) in several plant families have been found to be toxic to various pest species of insects through topical application, ingestion, and as fumigants. Previous studies revealed that, among various environmentally friendly insecticides, the EOs of Baccharis dracunculifolia and Pinus elliottii and an ethanol extract of Solanum granulosoleprosum plus Ricinus communis, were toxic to Ceratitis capitata and Anastrepha fraterculus (Diptera: Tephritidae) when applied topically to pupae or when ingested by adults. Here, we aimed to examine the potentially toxic effects of these plant-derived compounds when these two pestiferous fruit fly species were exposed to their vapors. We also examined their fumigant effect on female fecundity and fertility and compared it with water and ethanol controls. Exposure of C. capitata and A. fraterculus sexually mature adults to volatiles and vapors of both B. dracunculifolia and P. elliottii EOs resulted in lower longevity (half-life), survivorship, and female fecundity than the water vapor control. Toxicity of C. capitata was greater for P. elliottii than for B. dracunculifolia while the reverse was true for A. fraterculus. Exposure to vapors of S. granulosoleprosum + R. communis (S + R) had no effect on longevity but reduced survivorship of adults of both species. Interestingly, exposure to vapors of S + R, 50% (v/v) and pure ethanol resulted in greater fecundity of females of both frugivorous fly species than the water control. By contrast, fertility (% egg hatch) was in all cases high (>85%) and not different than the water control. Exposure to ethanol vapors appears to have similar effects on frugivorous tephritids as those reported on saprophagous and frugivorous species of Drosophila, a novel finding that may have important practical implications.

The present study investigated the patterns of microorganisms in an artificial larval diet during Dacus ciliatus (Diptera; Tephritidae) larval development. Microbial population contents in the diet of total heterotrophic bacteria, yeast and molds, coliform and lactobacilli, and their dynamics during development, were monitored. Initially, the microbial composition in diet trays failing to produce viable pupae and in trays successfully producing pupae and adult flies was characterized. The failing diet trays contained large populations of lactobacilli that increased during larval development, and low populations of coliforms. In contrast, the successful diet showed an increasing population of coliforms and a low, or undetected, population of lactobacilli. To study the hypothesis that lactobacilli affect D. ciliatus larval development, we conducted controlled inoculation experiments in which Lactobacillus plantarum was added into fresh diet at the time of egg seeding. L. plantarum inoculated trays showed no production of D. ciliatus. Control trays without lactobacilli inoculation showed variable results. One tray successfully produced viable pupae and adults, and showed a slight and slow increase in the indigenous populations of lactobacilli. The second tray, however, failed to produce pupae and showed a fast increase of the indigenous lactobacilli to very high levels. Monitored pH trends in L. plantarum-inoculated diet showed a sharp pH decrease during the first 4 days of larval development from 5 to less than 4 units, while successful diet, producing viable D. ciliatus pupae and adults, showed a moderate pH drop during most of the larval development period. The paper discusses the possible ecological interactions between D. ciliatus larvae, the microbial content of the diet and the physical properties of the diet. The discussion also points out at the usefulness of this approach in understanding and managing mass production parameters of tephritid fruit flies industrial diets used for Sterile Insect Technique.

Understanding the biology of the housefly (Musca domestica L.) is crucial for the development of mass-rearing protocols in order to use this insect as a degradation agent for livestock waste. In this study, the biological and genetic differences between different laboratory strains of M. domestica were analysed. Additionally, hybrids were obtained by mixing the strains and their biological parameters were also measured. The three strains of M. domestica presented differences in their biological and morphological parameters, the main differences were: size, egg production and developmental time. The strain A (specimens from Central Europe) had the best qualities to be used in mass-rearing conditions: it produced the largest quantities of eggs (5.77±0.38 eggs per female per day), the individuals were larger (12.62±0.22 mg) and its developmental time was shorter (15.22±0.21 days). However, the strain C (specimens from SW Europe) produced the fewest eggs (3.15±0.42 eggs per female per day) and needed 18.16±0.49 days to develop from larva to adult, whilst the females from strain B (from South America) produced 4.25±0.47 eggs per day and needed 17.11±0.36 days to complete its development. Genetic analysis of the original laboratory strains showed four different mtDNA cytochrome c oxidase subunit I haplotypes. Statistical parsimony network analysis showed that the SW Europe and South-American strains shared haplotypes, whereas the Central Europe strain did not. Upon hybridizing the strains, variations in egg production and in developmental time were observed in between hybrids and pure strains, and when mixing Central European and South-American strains only males were obtained.

Gall formation is associated with multiple changes in plant cells, which still requires a better understanding. In this study, galls caused by sexual generation (♀♂) of Neuroterus quercusbaccarum (L.) (Hymenoptera: Cynipidae) on pedunculate oak trees (Quercus robur L.) were used as a model. Cytoplasmic membrane condition, concentration of hydrogen peroxide (H2O2), the activity of antioxidant enzymes and amino acid decarboxylase as well as chlorophyll fluorescence parameters were determined. Changes in physiological and biochemical parameters were analyzed in foliar tissues with galls and gall tissues themselves and compared to control. The presence of galls on oak leaves caused an increase of lipid peroxidation level. A significant decline in H2O2 and TBARS content with the reduction of guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) activity were observed in gall tissues. The activity amino acid decarboxylase, i.e., LDC, ODC and TyDC varied between samples, which may affect the content of amino acids. The presence of N. quercusbaccarum galls caused an insignificant increase of the chlorophylls, carotenoids and anthocyanin contents, while the content of pigments and their ratios in gall tissues was extremely low. Moreover, photosynthetic parameters (F0, Fm, Fv/Fm, Y, qP) were significantly decreased. Data generated in this study indicate that the development of N. quercusbaccarum galls on pedunculate oak leaves has a negative effect on host plant related to the disruption of cell membrane integrity, disturbance of photosynthesis and reduction of the antioxidant potential of the host plant.

These crops are all either indigenous or of early introduction, except in the case of special varieties and they have achieved within the limits of their present distribution an equilibrium with their insect pests. Where there is no reasonable chance of a return for his labours, the native has ceased to grow a particular crop. This equilibrium is unstable, since pests increase in numbers at intervals owing to a variety of causes. For example, the introduction of cassava into new areas to prevent famine during the locust invasions brought to light the stem-borer moth, Opogona chlorophanes Meyr. In some cases cassava could not be grown and sweet potato had to be substituted. Acridids such as Eupropacris uniformis suddenly appear in great numbers at long intervals and do. considerable damage, then disappear just as suddenly. Similarly the adverse effect of climate on the crop will render it susceptible to particular pests, especially Aphids, during periods of drought. Agricultural practice is also concerned in this equilibrium, as for example where the time of planting legumes is governed by the attacks of various Galerucid beetles, particularly Ootheca bennigseni, Wse., which are most active during the early rains.

The daily distribution of G. pallidipes Aust. was studied on a spiral fly-round covering 180 acres in the South Busoga forest of Uganda in 1954–55. G. brevipalpis Newst. also occurred in the forest, and, rarely, G. palpalis fuscipes Newst. Seasonal changes occur in the size of G. pallidipes, but are less marked than those reported from other places. The size of G. brevipalpis also varies with season. Seasonal colour changes in G. pallidipes indicate that in the driest season about half the puparia experience relative humidity as low as 70 per cent.

Catching was done at 349 (later increased to 373) points on the spiral. Mathematically, the catches on a single day, or the sum of many days, conformed to a negative binomial distribution. Although this indicates an uneven distribution, it is pointed out that one negative binomial is compatible with many different distributions on the ground. For this reason the negative binomial is not a satisfactory summary of data which at present can only be shown satisfactorily on a map.

Comparison of maps of catches on successive days shows a confusing pattern of vague and ill-defined patches of flies moving about in an unpredictable fashion. A definitive pattern appears only when many days' catches are summed. Such apparently random movement explains the high variance between days' catches previously reported. Sometimes very large numbers of G. pallidipes were found in a small area. As an index of such concentrations, the smallest area which could contain half the day's total catch was determined. Arbitrarily, when half the day's total catch was found in 5 per cent, or less of the total area, a concentration was said to exist. During 16 months' work, concentrations of tsetse, as defined by this criterion, were observed 16 times. Sometimes, but not always, the concentrations followed immediately after the passage of a herd of elephants or buffaloes, and it is concluded that these animals probably caused these concentrations, although the manner in which they may do so remains obscure.

It has been shown that G. morsitans and G. tachinoides annually shift their breeding-ground in March from the edge of a residual forest island to the centre— a distance of some 40 yards. The move is associated with an increase in mortality amongst the last puparia to be found, death usually having occurred late in pupal life.

The object of the investigation has been to discover what prompts the female to move just before pupal mortality increases.

It has been found that there is little difference in the temperature conditions of the two breeding-grounds, but that the evaporation rate is one-third less in the centre of the forest. However, the abandonment of the forest margin is not explained by attributing to the female the ability to detect differences in the evaporative power of the air, but rather by the negative reaction to light developed by the whole community under conditions of universally high temperature. The period of migration coincides with an abrupt increase in the number of hours when the shade temperature is above 90°F. (32°C), the temperature at which Jack & Williams found that the negative reaction to light begins. During March the diurnal temperature is below this figure only immediately after dawn, when under laboratory conditions parturition rarely occurs. Since the temperature remains above 90°F. until well after activity has ceased at dusk, it is probable that at any rate the non-hungry tsetse spends most of the day and all the night in the centre of the forest. In the evenings field observations suggest that the stimulus of hunger may overcome the negative reaction to light, as then flies will undoubtedly attack in the forest edge, but since pregnant females rarely feed for several days before parturition, this counter-stimulus is unlikely to be operative at the time the female extrudes her larva.

By moving into the centre of the forest the adults will gain a reduction in temperature of only 3 or 4°F., but they will be less susceptible to heat, as the much lower evaporation rate will reduce their water loss.

The climatic conditions in the pupal environment of the forest edge at 1 ½ inches depth were found to favour survival, so it was concluded that the factor which inhibited emergence must have been operative before the puparia were formed. Possibly high surface evaporation and unsaturated soil atmosphere affect the formation of the pupal integument at the time of pupation, rendering subsequent emergence impossible.

The meteorological data collected in this investigation are more detailed and localised than anything yet published by the writer, and should give a better picture of the dry season adult and pupal environments in a locality which is very close to the hot, dry limits of the range of both species.

Puparia are found in large numbers in soils whose mean monthly temperatures range from 69°–82°F. (20·6—27·8°C). Field observations suggest that a constant temperature of 72°F. (22°C.) with a R.H. of 80 per cent., or 77°F. (25°C.) at R.H. 100 per cent., are conditions which should provide very healthy puparia if reproduced in the laboratory (see Appendix).

A review of the literature is given which shows that changes in the susceptibility ofinsects to insecticides occur during development when the poison is applied as a fumigant, as a stomach poison and as a contact poison.

The assessment of changes in susceptibility to contact poisons is discussed. The basis of assessment may be the concentration required to kill a given number of individuals, or the amount of poison required to kill unit weight of insect material. The great majority of the earlier work used the former basis of assessment, but where the insect is changing in size and shape during development and hence changing in the proportion of surface area to body weight, this method has limited significance when the poison is applied as a spray of constant deposit evenly over the surface area. A mathematical method is given for transforming the results obtained in terms of concentration to kill a given number of individuals into weights of poison to kill unit weight of insect material. Rearingmethods are outlined which enable batches of various stages of Diataraxia oleracea (L.) (tomato moth), Tenebrio molitor L. (meal worm) and Periplaneta americana (L.) (American cockroach) to be obtained at a known age and stage of development.

Experimental results are given for a spraying technique using DDT and the pyrethrins as insecticides on the comparative resistance of the eggs, larvae and pupae of D. oleracea, the larvae, pupae and adults of T. molitor and the nymphs and adults of P. americana.

On the basis of the concentration of insecticide required to kill a given percentage of individuals, it is shown that great differences can occur in the resistance of different instars of one species and considerable differences may occur within the instar. If the data for the larval and nymphal instars are considered on the basis of the weight of poison required to kill unit weight of insect material, differences still exist but are much reduced.

When toxicity is estimated on the basis of the concentration of poison in a constant spray deposit required to kill a given percentage of individuals the overall variations of resistance during development measured for DDT in terms of median lethal concentrations were: —D. oleracea eggs and larvae fifty times (0·002 per cent.–0·1 per cent. w/v), the pupa proved resistant to 0·5 per cent, w/v; T. molitor larvae, pupae and adults thirty-seven and a half times (0·0008 per cent.–0·03 per cent, w/v.) and P. americana nymphs and adults eight and a half times (0·0035 per cent.–0·03 per cent. w/v). The figures for pyrethrins were: D. oleracea eggs, larvae and pupae thirty-seven times (0·0027 per cent.–0·1 per cent. w/v), T. molitor larvae, pupae and adult forty times (0·005 per cent.–0·2 per cent. w/v), and P. americana nymphs and adults ten times (0·00031 per cent.–0·003 per cent. w/v).

The figures show that the range of variation of resistance during development may be very large, over 250 times in the case of DDT and D. oleracea, where the pupa, is resistant. The maximum variation that was found within an instar was 16·6 times where the resistance to pyrethrins of the 1-day old pupa of T. molitor was compared with that of the 4-day old pupa. The data show that the amount of variation in resistance that can occur varies with the test species and with the insecticide. Furthermore that the order of resistance of the developmental stages of any given species will differ with the insecticide and that with any given insecticide the order will vary with the species.

It may be inferred from these data that any comparison between insecticides on one stage of development of one instar of one species will not necessarily hold true of any other stage of development of that species or of any other species.

Observations were made on the action of the insecticides on the various instars and the symptoms of poisoning are described. It was observed that DDT at the highest concentration used (0·075 per cent. w/v) failed to prevent the development of the embryo inside the egg-shell and death only occurred after the fully developed embryo had eaten the egg-shell which it normally does prior to emergence. Pyrethrins on the other hand if applied at sufficiently high concentrations could prevent embryonic development although at lower concentrations a high percentage of eggs formed fully developed embryos.

At the highest concentrations used neither DDT (0·5 per cent, w/v.) nor the pyrethrins (2·5 per cent, w/v.) were able to prevent pupal development, and partial emergence often occurred before death. DDT differed from the pyrethrins in that it was ineffective on the pupae of D. oleracea.

Using data given in the literature and from some preliminary experiments on respiration rates, it was possible to deduce some correlation between metabolic rate and susceptibility, and changes in the permeability of the cuticle and chorion and susceptibility, but the evidence is unsatisfactory and the causes of the changes in susceptibility await further detailed investigation.

Development times and mortality factors were investigated for populations of Aedes scapularis (Rondani) occurring in natural temporary ground pools in southeastern Brazil. Analysis of life tables by the key-factor method showed that mortality caused by desiccation of breeding sites was the principal factor accounting for fluctuations in population sizes throughout the study period. For cohorts that completed development, mortality attributed to predation by aquatic insects ranged from 68 to 96% and was the most important cause of death. In these cohorts, final population size was determined by the high mortality rates that occurred during the fourth larval instar and pupal stages; however, the key-factor best accounting for the population fluctuations was predation of fourth instar larvae. The short mean time of 7.1 days for synchronous development of the larvae and the lack of evidence of density-dependent mortality suggested that the A. scapularis populations were not strongly regulated and can attain relatively high densities.

The locust infestation in Nigeria, from December 1929 to April 1931, is studied in relation to the climate and the following preliminary conclusions are made.

1. Humidity, precipitation and wind are the relevant climatic elements. Temperature does not seem of importance.

2. It is considered that the area of dispersal is limited by the humidity factor. With very few exceptions swarms remain where the mean relative humidity (9 a.m., L.M.T.) is not more than 85 per cent. and not less than 40 per cent., while most swarms are found where the humidity is from 60 per cent. to 80 per cent.

3. This humidity belt is similar to the area covered by three main types of vegetation and the swarms move across the belt according to the humidity changes.

4. Movement along the belt is largely caused by the prevailing wind.

5. Breeding does not commence after the dry season until the humidity rises to 60 per cent. and the degree of wetness, calculated from the monthly rainfall, reaches 2. Breeding does not occur if the humidity is above 80 per cent.

6. Through the dry season the adults seem unable to live much more than 22 weeks, and if optimum breeding conditions are not reached within that period death may occur.

7. Breeding towards the end of the rainy season follows some 11 to 15 weeks after the locusts become adult, so long as the humidity is not more than 80 per cent., and high humidity may cause a diapause.

8. Suitable local conditions during the dry season may allow a third breeding season.

These conclusions may be utilised in the following ways :—

1. To delimit the total area likely to be infested.

2. To forecast when the different zones will be infested by flying swarms.

3. To forecast whether and when breeding is likely to occur in each locality.

4. To check whether unidentified swarms were of this species of locust.

5. To test the possibility of one suspected breeding ground having been infested from another.

During 1958–60, replicated insecticide trials were carried out in East Anglia in an attempt to assess seed losses on Trowse mustard (Brassica juncea) caused by larval infestations of the cabbage stem weevil, Ceutorhynchus quadridens (Panz.). The overwintered adult weevils invade the young growing crops during April and May, and the eggs are laid in the petioles over a period of weeks, depending both on temperature and crop stage, until about mid-June. Egg-laying began on mustard when the plants had produced six to seven broad leaves, but the actual time at which the first eggs were laid seemed to depend mainly on temperatures during May. In the insecticide trials, infestations averaged up to 26 larvae per plant, and none of the untreated plants entirely escaped attack.

High rates of γ BHC (5 or 10 per cent, of the weight of seed) gave some control of stem-weevil larvae when kerosene was used as the sticker for the insecticide; 3 per cent, or 5 per cent, phorate and 5 per cent. Telodrin (1,3,4,5,6,7,8,8-octachloro-3a,4,7,7a-tetrahydro-4,7-methanophthalan) gave no control. The control by seed dressing was unreliable and is considered unsuitable for assessing yield losses caused by stem weevil.

A single emulsion spray of dieldrin applied during May when the first adult feeding holes were found in the petioles, gave a good control of stem weevil and prevented egg-laying, and this technique seems promising for future work on damage assessment. It is thought, however, that sprays specifically directed against stem weevil would seldom be justified economically on commercial crops of Trowse mustard, but on April-sown crops the first dieldrin spray against blossom beetle, Meligethes aeneus (F.), may give some protection against stem weevil.

The damage-assessment experiments gave no reliable indication of the effects of the stem weevil on yields of seed, in spite of their being sited in localities known to have a high weevil population. It was clear, however, that sowing date greatly influenced yields of seed; plants sown in March outyielded those sown in April or early May.

The black citrus aphid, Toxaptera aurantii (Boy.), produces a distinct scraping sound by rhythmic movements of whole colonies. It is the only species of aphid known to produce audible sounds and the acoustical content of a preliminary recording of these sounds is reported in detail. During one recording the aphids stridulated 15 times in 21 seconds, giving an average period of 1–4 seconds between emissions and this rate remained virtually constant for at least an hour. Analysis of the recording established a clear peak frequency band at about 4–6 kHz with another around 800 Hz-1 kHz and possibly another in the ultra-sonic range above 18 kHz. Morphological adaptations of the abdominal cuticle and of the hind tibiae to form a stridulatory apparatus are illustrated and possible functions of stridulation as a defence mechanism or as a means of intraspecific communication are briefly discussed.

In summarising, the following points are to be noted:—

1. The thermal death point of the blow-fly was definitely influenced by the factor of humidity.

2. Saturated and dry air had the effect of lowering the thermal death point.

3. Relative humidities from 60 per cent. to 80 per cent. were more favourable, while relative humidity of 70 per cent. actually was found to be an optimum point.

4. From the weighings it may be concluded that death in saturated air was due to the inability of the flies to regulate their heat by evaporation.

The breeding-place of Simulium neavei Roub. has remained undisclosed, despite many attempts to discover it, ever since Dr. S. A. Neave first collected the females in 1911. In May of that year Neave made collections near the Yala River, Kenya, and in November of the same year caught more specimens in Western Ankole, Uganda. Roubaud described and named the species in 1915. Dry in 1921 captured some specimens feeding on man at Ngoina, near Kericho, Kenya, and made the important observation that the local natives connected the fly with the occurrence of a chronic skin disease in this district which has since been identified as onchocerciasis.

The Sudan dura (millet) bug, Agonoscelis versicolor, F., a member of the family Pentatomidae, Hemiptera Heteroptera (Rhynchota), is an important pest of millet. Its depredations vary from year to year, depending chiefly upon the rainy season, but every few years it causes serious losses of millet (Sorghum vulġare and Sorghum sp.), which is the main food crop of the Northern Sudan.

This bug is widely distributed in Africa, but so far as the writer is aware, it is only in the Sudan that it occurs as a serious pest of grain, or, indeed, as a serious pest at all. In view of this, and the little work that has been done upon it, it was felt advisable, when a severe outbreak took place in 1927, not only to concentrate upon the control but also to effect as complete a study as possible of the bionomics and essential morphology of the bug.

Upon completion of the work it was found better to publish the results as two separate papers : (1) A Sudan Government Entomological Bulletin, giving an account of the bug as a pest in the Sudan, the control measures carried out, the bionomics and parasites ; and (2) a paper for publication in a scientific journal giving the results of the morphological studies, and their relation and application to the bionomics of the insect. The present paper is the result of the latter study.

Four new species of Encarsia, E. lanceolatasp. n., E. paracitrellasp. n., E. pseudocitrellasp. n. and E. unicitrellasp. n. are described and illustrated. All four parasitoid species were reared from the Bemisia tabaci-complex and/or other whitefly hosts in the Neotropical region. Encarsia paracitrella, E. pseudocitrella and E. unicitrella are extremely closely related, to each other and to E. citrella (Howard). A diagnosis is therefore given for the E. citrella-complex, with a key to the four currently included species. For E. citrella (Howard) a lectotype is designated, the male is described and illustrated for the first time, and the female is redescribed and illustrated. A key and a modification to an existing key are provided to facilitate the identification of the five species treated.

During investigations on the economic position of Collembola a significant attack on mangolds by one species of this group occurred at Rothamsted in the classical mangold field known as Barn Field. The particular species involved was Bourletiella hortensis, Fitch (pruinosus, Tullb.). Although the economic position of Collembola has not, as yet, been fully established, this member of the order can claim priority in the list of previously reported economic species. The first British record of injury probably by this species is that of Miss Ormerod in 1894, when she reported leaf damage to turnips in Scotland. Since then British records include as host-plants sweet peas, beans, radishes, lettuce, mangolds and soy beans. Reports from America confirm the economic position of this species, and in Canada Macnamara states “ the list of plants it is known to injure reads like an index to a seedsman's catalogue : beans, beet, cabbage, cantaloupes, carrots, clover, corn, cucumber, kale, lettuce, mangolds, onions, peas, potatoes, radishes, rye, spinach, squash, tobacco, tomatoes, turnips, violets, watermelons, wheat, wild cucumber.”