The larvae of the Melolonthid beetle, Lachnosterna. consanguinea (Blanch.), have been found to be very destructive to sugarcane in the Dalmianagar area in Bihar, India, since 1956 when they were first recorded there. The pest has since been found to occur in serious numbers in certain adjoining areas and also in Bihta in Patna district. Damage is done by the larvae by feeding on cane roots. Heavily infested cane clumps dry out completely and in severe infestations as much as 80 per cent, of the crop is lost. The infestation occurs only on light sandy soils; crops on clay soils are not affected. The February-planted crop suffers more seriously than that planted in October. The adults have not so far been observed doing any damage to sugarcane.

The emergence of adults starts in the last week of April, but a rush of emergence occurs only after the first shower of rain. The adults are nocturnal in habit and feed on leaves of certain bushes and trees during the night. They hide themselves in loose moist soil in day-time. Mating takes place after dusk during the flight season, and eggs are laid in the soil at a depth of 5 to 10 cm. The incubation period varies from 8 to 10 days. The young larvae move to cane roots after some initial feeding on grass roots. They are fully grown in 8 to 10 weeks' time when they move deeper into the soil and pupate in earthen cells at a depth of 0·3 to 1·5 m. The pupal period varies from 12 to 16 days and the pest overwinters in the adult stage. There is only one brood a year.

The adults are active at night and are attracted to artificial light and can be destroyed in large numbers with the help of light-traps. Collections from the foliage of trees and shrubs at night is an easier and better method of destruction. Trials with insecticides applied as sprays to the foliage of shrubs in cages to which adults were immediately introduced showed that a suspension containing 0·5 per cent. DDT was effective and was superior to one of BHC.

Replicated field trials carried out for the control of the larvae with various insecticides showed that BHG applied to the soil in a dust at the rate of 22·4 Ib. toxicant per acre was the most effective. This treatment, when applied-at planting time (February) had an adverse effect on germination; this effect was not observed when the application was made at the end of May. In subsequent replicated experiments, when BHC in a dust was applied in two instalments at the rate of 10 Ib. per acre at the end of May at the time of the rush of adult emergence, and in July, respectively, much better results were obtained without any adverse effect on the crop. BHC and other insecticides applied to the soil in sprays at 10 Ib. per acre at the end of May were ineffective.

Amongst varieties of cane grown at the Bank Farm, Dalmianagar, Co.935 and B.O.3 showed a greater tolerance of injury by the larvae than the others.

A Scoliid, Scolia aureipennis Lep., was observed to parasitise the grubs during September. The rate of parasitisation was only about 5 per cent.

A disease caused by a fungus, Metarrhizium. anisopliae, was also observed to occur in the adults. Affected beetles died within 4 to 6 days.

The common Indian toad (Bufo melanostictus) and the gecko (Gecko gecko) were seen preying on the adults in the evening when these were active. A number of birds, particularly the Indian crow (Corvus splendens) and mynah (Acridotheres tristis), also feed on the larvae when these are exposed during tillage operations.

Aphids belonging to the species Nasonovia ribis-nigri (Mosley), Aulacorthum circumflexum (Buckt.), Macrosiphum euphorbiae (Thos.), Myzus persicae (Sulz.) and A. solani (Kalt.) were exposed to attack by the parasite, Monoctonus paludum Marshall, and were sectioned and dissected at various time-intervals after attack in order to observe the developmental processes of the parasite.

The egg was always laid in the posterior mass of fused ventral nerve ganglia in the thorax of the aphid host.

The development of the parasite in N. ribis-nigri, its normal host on lettuce, is described.

In the species A. circumflexum the development of the parasite was arrested after approximately 24 hours by the secretion around it of a thin brown capsule formed by certain of the host's blood cells.

In the other three species, Macrosiphum euphorbiae, Myzus persicae and A. solani, no capsule formation occurred. The development of the parasite embryos was rather variable in these but it was common for parasites in Macrosiphum euphorbiae to reach the stage normal for 24-hour embryos and for parasites in Myzus persicae and A. solani to reach stages rather less advanced than this before degenerative changes set in.

The degenerative changes in the parasite embryos are described for each species of aphid and the nature of these changes is discussed.

A description is given of a new species of Elachertus, E. agonoxenae (Chalci-Doidea, Eulophidae), on the basis of adults reared from larvae of Agonoxena pyrogramma Meyr. in New Guinea and Agonoxena sp. in Queensland. This species has been imported into Fiji for trial in controlling A. argaula Meyr., a pest of coconut palms. The new species is compared with E. argissa (Wlk.) and E. artaeus (Wlk.), two British species for which lectotypes are here selected.

A major problem in using larvicides to control Culicoides is to recognise the sites requiring treatment. The relationship between plant cover and breeding of Culicoides (mainly C. impunctatus Goetgh.) was accordingly investigated in moorland areas of Scotland. Two sites were examined on Soutra Hill, Midlothian, and one each on Bannachra Muir and at Luss, Dunbartonshire. Three vegetational zones were recognised on Soutra (site 1): bogland (I), acid grassland (III) and a zone (II) characterised by vegetation preferring a much wetter habitat than either of the foregoing. C. impunctatus was virtually the only Culicoides species found in zone I; it was relatively less abundant in zone II, where C. albicans (Winn.) reached its peak, and occurred most densely at the bogland edge of zone III, where it was associated with C. cubitalis Edw., C. heliophilus Edw. and C. obsoletus (Mg.). Further into the grassland, C. impunctatus decreased while the other three species became more numerous and other species, of the group of C. pulicaris (L.), appeared. Within each main zone there were no significant differences between the various floristic groups as regards larval densities.

Fluctuations in population density observed in late autumn were regarded as more apparent than real, and attributable to larval movement in response to an oscillating factor, possibly soil-water level. This movement was recognisable in all zones but was most strongly marked where the ground was uneven.

On Soutra (site 2), where only zones I and III were sampled, there was remarkable consistency among the larval densities of the various groups of samples examined. This applied whether the samples were classified on their angiosperm flora, moss cover or spatial arrangement. The main source of variation was within groups and it was found that two adjacent small plots (12 yd. & z.Times; 12 yd.) which were macroscopically identical showed consistent differences over a period of ten months, covering the transition from one generation to another.

On Bannachra Muir, the larvae of C. impunctatus were concentrated in an area covered by Juncus articulatus and Sphagnum where the water flowed down the hillside near the surface. C. impunctatus avoided both an area of drier leaf mould and a stagnant ditch. C. albicans, C. heliophilus and C. obsoletus preferred the ditch to the hillside flow.

Around a hillside trickle at Luss, larvae of C. impunctatus and C. truncorum Edw. were abundant in subequal numbers. In spite of the restricted size of the area (about 10 sq. yd.) they never occurred in equal numbers in any set of samples, but one or the other predominated. C. truncorum showed a preference for the very wet parts.

A series of experiments was undertaken to examine the relative concentration of cotton flea-beetles (Podagrica puncticollis Weise and P. pallida (Jacoby), Halticinae) within cotton fields in the Sudan Gezira in 1954 and 1955. Assessments were carried out on the flea-beetle populations and on the damage done by them, and evidence is produced to show that the use of a damage assessment in the first three weeks of the life of the cotton plant is more satisfactory in a large-scale experiment than beetle counts. The assessment lasted for between three and four weeks after the emergence of the seedling cotton.

It appeared that the beetles tended to leave cotton 19 days after sowing. Damage within the cotton field was at first in accord with the sowing differential, but then shifted against this as the flea-beetles moved on to the later-sown cotton as this became more attractive.

The peak population of flea-beetles occurred during the last few days of August and the first few of September when the first-sown cotton was 14–18 days old, and this suffered more damage than the later-sown and less attractive cotton. Differences in the level of attack on the four sowings tended to even out, but did not do so completely as the flea-beetle population was declining.

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.

Laboratory studies are reported on Syntomosphyrum albiclavus Kerrich, a Eulophid of interest as a pupal parasite of tsetse flies. Material for a laboratory culture was obtained from puparia of Glossina morsitans Westw. collected in Tanganyika and sent to London by air.

‘ Natural’ and ‘unnatural’ hosts of this parasite were investigated. S. albiclavus parasitised all species of Cyclorrhaphous puparia offered in the laboratory, but has only been recorded from puparia of Glossina under natural conditions. The conditions which make a host suitable for S. albiclavus are discussed. The most important of these is the presence of the ‘sub-puparial space’ in which the eggs are laid, without which the host is unacceptable. S. albiclavus will also breed on dead pupae and in puparia containing other parasites.

The number of parasites emerging from the host puparium is shown to be directly proportional to its weight.

The fecundity of S. albiclavus is shown to be very variable and dependent upon the weight of host material consumed during larval life, which, in turn, reflects the density of parasites in the host puparium from which the females emerged.

The duration of the parasitic phase of the life-cycle and the length of life of the adults are shown to be functions of the temperature. Length of life is also affected by the relative humidity, increased mortality occurring in low humidities and in saturated air, with an optimum for survival at about 80 per cent. R.H.

It is shown that a constant temperature of 35°C. is fatal to the eggs of S. albiclavus.

The age at which females of S. albiclavus become mature was investigated at three temperatures and it is shown that the rate of maturation of the ovaries is a function of the temperature.

At 25°C., females of S. albiclavus are unable to lay eggs until the third day after emergence. The number of offspring produced then falls off with increasing age of the female and very old females, although attacking hosts, are unable to oviposit.

Two experiments in which G. pallidipes Aust. was caught on oxen, in Morris traps and on a fly-round in south-eastern Uganda are described.

Fewer flies were caught in traps than on oxen, but the former took a higher proportion of females. The numbers in traps covered with natural-coloured hessian tended to be greater than in traps on which the hessian was painted black. A white ox attracted fewer flies than darker-coloured oxen, among which a red ox was the most attractive. Variations reflected in day and site effects indicated that the sexes were differentially affected by the factors controlling availability to the oxen and the traps. Fly-round data appeared to give an unsatisfactory estimate of the population density.

The numbers caught by the various methods were, in general, not correlated and this casts doubt on the validity of fly-round or trap data as estimates of the number of G. pallidipes likely to attack cattle.

Carcelia evolans (Wied.) is a common parasite of Diparopsis watersi (Roths.) in Northern Nigeria. The egg and early larval stages have not been observed, but the latter are thought to be passed in the larva of the host. The fully grown parasite larva appears to leave its host after the latter has entered the soil and formed its pupal cell, and either immediately before, or after, the host pupates. The parasite puparium is thus formed inside the pupal cell of D. watersi, but outside the host. Before forming its puparium, the parasite larva excavates a pit in the wall of the cell, thus facilitating the subsequent exit of the adult fly, which can push through the weakened cell at this point.

The life-cycle of C. evolans is closely adapted to that of its host, with short-term generations during the cotton season alternating with a long-term, or diapause, generation during the dry season. It is believed that C. evolans goes into diapause as a minute first-stage larva, but the factors that induce diapause are unknown.

The short-term pupal period of C. evolans (12–14 days) was less variable than that of D. watersi (11–31 days) at 27±5°C. In dry conditions, inside and outside the laboratory, the mean duration of diapause for C. euolans (27·3–38·8 weeks) was longer than that of D. watersi (22·9–36·2 weeks). In pupation troughs, approximating to field conditions, the mean duration of diapause in D. watersi (43·2 weeks) was greater than that of its parasite (36·1 weeks). The spreadover of emergence of the parasite from pupation troughs was more regular than that of moths, with no peak in October.

Earlier estimates of the incidence of parasitism at Samaru are probably inaccurate because adult flies have now been shown to be capable of escaping through the apertures of the perforated zinc of the cages then in use. Estimates of the rate of parasitism, made in southern Katsina, showed that 23·1 per cent, of pupal cells obtained at Daudawa between 13th November and 24th December 1959 from cotton that had earlier been treated with insecticidal sprays were parasitised, compared with 30·7 per cent. of those obtained in the same period from unsprayed cotton four miles away. The rate of parasitism was particularly low (16 per cent.) amongst the larvae collected at Daudawa in November, due possibly to the insecticide applications that had been made earlier in the season.

These results imply that the parasite is easier to kill than its host, and an increasing use of insecticides on cotton in Northern Nigeria may therefore adversely affect the degree of control achieved by the parasite.

When non-teneral male flies of Glossina pallidipes Aust. were caught concurrently on oxen and in Morris traps in two experiments in south-eastern Uganda and classified, within 1½ hr. of capture, according to a modification of the hunger-stage categories described by Jackson, individual recorders were found to differ markedly in their assessments. No conclusions regarding the hunger stage of flies taken by different attractants could therefore be drawn from the first experiment, but in the second, which was so designed as to discount possible bias amongst recorders, the proportions of ‘hungry ’ (stage III + IV) flies in catches of males were similar on variously coloured individual oxen, and generally higher than in trap catches, in which the proportions varied widely. As all the traps appeared identical, no generalisation is possible about the mechanism by which non-teneral male flies are attracted to and induced to enter such traps.

A series of catches of G. pallidipes Aust. was made in 1½-hr. periods between 0800 and 1830 hr. each day during two experiments carried out in the early wet season (1957) and the late dry season (1958), at Lugala, Uganda, using tethered, small, shorthorned East African Zebu oxen, Morris traps and the standard flyround technique.

Flies were attracted to the oxen in greater numbers in the morning and evening than at midday, the evening increase being marked in the wet season. The daily catches of both sexes on oxen, though starting at much the same level in both seasons, fell to lower levels at the hotter times of day during the dry season and rose only slightly in the evening. Traps, on the other hand, in both seasons caught most females between 1230 and 1400 hr. and least in the mornings. Male flies were trapped in greatest numbers between 1400 and 1530 hr. in the wet season, but only in comparatively small numbers at any time in the dry season, though there was a suggestion of maximum availability between 1100 and 1230 hr. during the latter. During the dry season, catches on the fly-round and on oxen showed a similar periodicity in the case of females, but not in that of males, fly-round catches of which declined from a peak at 0930–1100 hr.

In order to evaluate Morris traps as a method of investigating populations of Glossina pallidipes Aust., and to compare them with fly-rounds, a series of catches was made by both methods in and adjacent to an area of evergreen thicket covering about three sq. miles in the Lambwe Valley, South Nyanza District, Kenya. During the period of the investigations (February 1955-February 1958), the mean monthly apparent density (catches of non-teneral males per 10,000 yd. traversed) determined from a fly-round 5,200 yd. long traversing the thicket varied from 70 to 1,300, and the mean monthly trap catch, determined from 26 traps along a similar traverse but over a shorter period, varied from 190 to 670. Catches by the two methods showed similar fluctuations but were not significantly correlated, and it is not certain that real changes in population occurred. The distribution of G. pallidipes between the three main vegetation communities sampled appeared different when studied by traps, or by other methods (fly-rounds, and searching for resting flies). The two latter methods were in agreement, but traps gave different results, perhaps because one of the vegetation communities may have had a high proportion of productive trapping sites.

Dispersal of G. pallidipes into the surrounding, sparsely wooded grassland was studied by traps arranged in lines extending east and west of the thicket and at right angles to its edge. Traps appeared not to attract flies over a distance as great as 100 yd., but to catch only those that chanced to be in their immediate vicinity. Total catches in three traps over 10 months at distances of 5–100–300–500 and 900 yd. west of the thicket edge were 15,417–965–153–89 and 56, respectively; smaller numbers were taken up to 2,500 yd., the greatest distance investigated. Dispersal was greatest in the wet, cool half of the year.

In catches of G. pallidipes made in six consecutive two-hour periods daily for one year in two batteries, each of seven traps, and on two short fly-rounds, one of each along the east and the other along the west edge of the thicket, the traps yielded 78 per cent, females and the fly-rounds only 17 per cent. There was a marked tendency for females to be caught earlier in the day than males by either method, and for the pattern of catches to be earlier on fly-rounds than in traps. No difference in age, estimated by wing fray, was found between flies caught, by either method, at different times of day.

The total number of G. pallidipes caught by two traps operating 11 hours per day for 10 days at the thicket edge was over four times that caught there concurrently by a stationary party of three men.

It is concluded that traps are valuable because they catch a high proportion of females, thus affording information not given by fly-rounds, and operate continuously, at a higher over-all catching rate than that of men, thus facilitating the study of sparse populations. Nevertheless, site effects and day-to-day variability are both large with traps, so that reproducible results are difficult to obtain.

Experiments carried out in south-eastern Uganda, as part of a series of investigations of factors affecting the catch of Glossina pallidipes Aust. by Morris traps, showed that this was not significantly affected by varying the interval between emptying the traps within the range 1½-24 hours or by varying the width of the entrance slit from ¼ to 1½ inches. Such exceptions as occurred could be attributed to unexplained variations in the intrinsic performance of individual traps. Almost no flies were trapped at night (1830–0630 hr.).

Catches in traps with simulated defects (leaving the sleeve open or making holes in the cage gauze) were lower than in perfect traps; the catch was not significantly affected by the diameter of the sleeve opening, but was significantly lower in traps with 16 ½-in. holes in the cage gauze as against those with 2, 4 or 8. Escapes through such holes were observed whilst emptying the traps, when the recorder's approach disturbed the trapped flies, which were otherwise inactive. Frequent visits to the traps to empty them did not materially increase the number of flies effectively trapped, as might have been expected were flies escaping continuously or were the traps to catch flies accompanying the observer.

When the interval between emptying traps exceeded 24 hr., losses of trapped flies occurred, to an extent that is unknown but sometimes substantial, as a result of predation by ants; this is the most likely source of significant variation in catches made by apparently identical traps, and can be overcome by mounting traps on greased, single legs. When thus protected, there was no significant difference in catch between traps cleared at intervals ranging from 12 hr. to eight days. The longer this interval, the greater the proportion of dead amongst captured flies; the median length of life after capture was about two days, this period varying slightly with sex and more substantially with undefined differences between sites and trapping periods.

The Cicadellid, Empoasca lybica de Berg, is an important pest of cotton in the Sudan Gezira, where over 300,000 acres of cotton are grown annually under irrigation. Cotton is sown in mid-August, and the plants are uprooted and burnt the following May. The life-cycle of E. lybica from egg to gravid adult takes 16–24 days, and the adults live for up to 40 days. There is no diapause. During the 100 days from late August to early December when breeding on cotton is of economic importance, a single male and female could give rise to some 50,000 progeny.

During May to July, when crops are confined to irrigated gardens and river banks, E. lybica is widely distributed in such places and can be found also on tree hosts, which are numerous especially in the southern Gezira and along river banks. There is circumstantial evidence of displacement over long distances, and the great majority of catches of E. lybica in sticky traps were made before the increase in population on cotton that occurs from September onwards.

Of the 53 species of host-plants that have been recorded, only Solanum dubium, Rhynchosia memnonia, Hibiscus spp. and Abutilon spp. are of importance in the ecology of E. lybica. The first two especially are common weeds in fallows, which comprise more than half the land under rotation. Populations of E. lybica in Gezira fallows at the time of cotton germination tended to be greatest where pre-sowing rains (i.e., those falling from 1st July to 15th August) were highest. Correspondingly, initial infestation of cotton was highest in seasons and places receiving the most pre-sowing rains, although density of infestation in any place was affected by sowing date and proximity to irrigated fields and gardens which supported weed host-plants.

In order to develop a system of sampling for infestations of E. lybica in the cotton crop, the distribution of nymphs on cotton plants was examined. It was found that nymphs were most numerous in the leafiest zones of the plant and a random choice of leaves seemed an appropriate means of sampling for infestation. The distribution of nymphs within and between cotton fields was also investigated and a standard sampling procedure adopted.

Peak infestations on cotton could not be predicted from the level of initial colonisation, or from surveys a month later. Peak infestations were usually inversely related to the level of initial colonisation, especially when comparisons were made between seasons, as at the Gezira Research Farm. That is to say, high levels of initial infestation, which occurred in seasons of good pre-sowing rains, tended to be followed by low rates of increase, and in years of poor pre-sowing rains, initial infestations tended to be low and rates of increase high.

The relationship of these findings to those of Cowland & Hanna (1950) and Hanna (1950) are discussed; the hypothesis that pre-sowing mud-splash is a major factor controlling numbers of E. lybica in the Sudan Gezira is discounted, although it is accepted that this factor temporarily reduces populations.

The rate of increase of infestations of E. lybica was found to be positively correlated with the concentration of nitrogen recorded 2–4 weeks previously in the cotton leaf. This concentration affected not only the rate of increase of the initial colonisers, but also the rate of recovery of populations during November and December after spray-applications of DDT. The nitrogen concentration in the leaf was increased by nitrogenous fertiliser, with a corresponding increase in infestations of E. lybica. It was also found to be negatively correlated with pre-sowing rains, which, if low, prevent the nitrate in the top 12 in. of Gezira soil being washed to lower levels, but the data presented provide no evidence that the relationship is causal.

It is concluded that localities and seasons of poor pre-sowing rains favour a high rate of increase of small populations of E. lybica because of high nitrogen concentration in cotton leaves during September and October. This tendency is augmented by application of nitrogenous fertiliser. A regression equation relating the peak infestations of E. lybica with pre-sowing rainfall and with nitrogenous fertiliser is given and the infestations computed from this are shown not to differ significantly from those recorded in the Gezira as a whole, and in the four main divisions of it separately, during the eight years 1949–1956.

Gamma BHC, aldrin, dieldrin, endrin, DDT and parathion have been tested as seed dressings in field experiments for the control of wheat bulb fly, Leptohylemyia coarctata (Fall.), in eastern England. The concentrations ranged from 20 to 70 per cent, and the dressings were applied at 2–3 oz./bushel.

At concentrations of 40 per cent, or over, the first three materials appreciably reduced attack and at high infestations increased yield; within the period October to January their effectiveness increased the later the wheat was sown. There was evidence that they were less effective on highly organic soils. The other materials were either less effective or had other disadvantages.

Seed dressings of γ BHC usually reduced the number of larvae entering the plant but had little effect on larvae which succeeded in entering. Aldrin and dieldrin and probably most other materials usually had less effect on the entry of larvae but were very effective in killing larvae after entry so that the plant could subsequently recover.

Combine-drilling of aldrin or dieldrin affected the larvae in the same way as seed dressings; in one season on a peaty soil seed dressings were more effective than combine-drilling, but in another season on a mineral soil seed dressings were slightly less effective than combine-drilling. However, it was clear that with combine-drilling very much higher quantities of insecticide per acre were needed to achieve a comparable result. Both aldrin and dieldrin gave similar results.