Variations in density of adults of Anopheles merus Dön. in Jimbo Village on the Kenya Coast were found to be correlated both with rainfall and with salinity at their breeding sites. Densities started to increase at the beginning of the rains when several breeding sites were formed. This was followed by a decline in numbers resulting mainly from the decrease in salinity in the semi-permanent breeding sites. A second rise occurred after the end of the rains, corresponding with an increase in salinity in the semi-permanent breeding sites due to evaporation. Peak density coincided with salinities of 30–50% sea water in the breeding sites. Laboratory breeding experiments showed that the larvae were usually capable of completing development in 0–100% sea water, with optimum development at 0, 40 and 60% sea water. Failure to complete development in 100% sea water at certain periods of the year indicated that there could be some seasonal variation in salt tolerance. The larvae were also found to complete development in alkaline saline water collected from an inland location around Lake Jipe in Kenya. The LC50s of sea water for first and fourth-instar larvae after exposure for 2 h were 135·0 and 930·0%, respectively. First-instar larvae were less to lerant of sodium chloride than of sea water of equivalent strength. The LC50 of sodium chloride for first-instar larvae was only 102·5%, sea water equivalent. In tests against first-instar larvae of other soluble chemical salts normally present in sea water, the highest LC50 (122·0g/litre) was of sodium sulphate and the lowest (10·5g/litre) of potassium carbonate.

The flight performance of a laboratory population of Triatoma infestans (Klug) was tested on a flight balance. Bugs adopted a typical flight posture which is described. They were capable of steady flight and produced reasonable amounts of lift. Flight durations were generally short, but capacity for flight rose to a peak in the third week after adult eclosion with the longest recorded flight being one of 2 h 40 min by a male. Sexual differences were slight; males had a slightly higher mean wing-beat frequency (57·8 Hz against 55·6 Hz), and a few more females than males made longer flights. Differences were noted between short and long fliers; the latter producing significantly more lift and showing signs of a flight pattern divisible into rising, steady and falling phases. The short fliers showed only rising and falling phases. Lift and wing-beat frequency were correlated, but it is evident that lift also depends on other variables such as stroke-plane angle, body angle and wing-beat amplitude, which are discussed.

Field studies suggest that the generalist carabid predator and scavenger Pterostichus melanarius Illiger aggregates to patches with a higher density of slug prey. The mechanisms behind such aggregation are unknown. Experiments were conducted to test the hypothesis that they are responding to chemical cues. Electroantennograms (EAGs) showed no response by P. melanarius antennae to live, nematode-infected, injured or freshly killed slugs, but a strong response to dead slugs that had been allowed to decay for up to 48 h. Such a response would enable the beetles to find carrion in the field and may also, as dead prey are likely to be spatially correlated with live ones, provide a mechanism by which P. melanarius finds patches with a higher density of live slugs. Subsequent video analyses of P. melanarius responses to patches of slug mucus within arenas showed that beetles with intact antennae could detect these patches because they spent more time, and moved greater distances, within them and increased their rate of turning. Thus, at close range, P. melanarius used their antennae to detect slug mucus and hence, by implication, live slugs. The apparent contradiction between EAG data and behavioural experiments is discussed. Together these result confirm that P. melanariusdoes respond to chemical cues from its slug prey in ways that could lead to aggregation in areas of higher slug density in the field.

Changes in the genetic structure and genotypic variation of the aphid Sitobion avenae collected from cereal crops in northern France were examined by analysing variation at five microsatellite loci across several years and seasons. Little regional and temporal differentiation was detected, as shown by very low FST among populations. Repeated genotypes, significant heterozygote deficits, positive FIS values and frequent linkage disequilibria were found in nearly all samples, suggesting an overall pattern of reproductive mode variation in S. avenae populations. In addition, samples from Brittany (Bretagne) showed greater signs of asexual reproduction than those from the north of France, indicating a trend toward increasing sexuality northward. These patterns of reproductive variation in S. avenae are consistent with theoretical models of selection of aphid reproductive modes by climate. Contrasting with little changes in allelic frequencies, genotypic composition varied substantially in time and, to a lesser extent, in space. An important part of changes in genotypic arrays was due to the variation in frequency distribution of common genotypes, i.e. those that were found at several instances in the samples. Genotypic composition was also shown to vary according to climate, as genotypic diversity in spring was significantly correlated with the severity of the previous winter and autumn. We propose that the genetic homogeneity among S. avenae populations shown here across large temporal and spatial scales is the result of two forces: (i) migration conferred by high dispersal capabilities, and (ii) selection over millions of hectares of cereals (mostly wheat) bred from a narrow genetic base.

Helicoverpa armigera is a pest of several crops causing significant economic impact. We evaluated the insect development on different vegetative and reproductive structures of cotton, maize, and soybean compared to artificial diet. One hundred individuals were evaluated per structure (cotton leaves and bolls; maize leaves, grains, and silk; soybean leaves and pods) and artificial diet. Centesimal analyses were performed on quantifiable nutrient contents in diets. The viability of immatures (eggs, larvae, and pupae) ranged from 30% on maize leaf to 74% on cotton bolls, while on the artificial diet, it was 70%. Maize, cotton, and soybean leaves provided viability of 30, 37, and 42%, respectively, revealing these leaves tissues are less favorable to the development of H. armigera immatures compared to ‘reproductive tissues’. Centesimal composition of diets compared 14 common components in all diets, which correlated significantly with larval and pupal stages and/or pupal weight. Of the 12 dietary components that significantly affected larval development time, half were negatively correlated, indicating a decrease in developmental time from their increments. In general, when insects were confined separately to substrates, the artificial diet was the most suitable for H. armigera development compared to the evaluated natural diets. However, in natural conditions, the variability of available hosts must be considered. In addition, it is acceptable for moths to select more suitable hosts for oviposition, while their larvae move to other more suitable tissues of the same plant or even migrate to other plants.

Area-wide sterile insect technique (SIT) programs assume that offspring reduction of the target population correlates with the mating success of the sterile males released. However, there is a lack of monitoring tools to prove the success of these programs in real-time. Field-cage tests were conducted under the environmental conditions of the Mediterranean coast of Spain to estimate: (a) the mating success of sterile Vienna-8 (V8) Ceratitis capitata males using molecular markers and (b) their efficacy to reduce C. capitata populations under six release ratios of wild females to wild males to V8 males (1:0:0, 1:1:0, 1:1:1, 1:1:5, 1:1:10, and 1:1:20). Statistical models were developed to predict: (a) the number of females captured in traps, (b) sperm ID (sterile or not) in spermathecae of the trapped females, and (c) the viable offspring produced, using release ratio and temperature as predictors. The number of females captured was affected by relative humidity. However, its influence in the model was low. Female captures were significantly higher in ratios 1:0:0 compared to ratios where V8 males were released. The proportion of V8 sperm in spermathecae increased with temperature and with the number of V8 males released, but leveled off between ratios 1:1:10 and 1:1:20. In all seasons, except winter (no offspring), viable offspring increased with temperature and was lowest for ratio 1:1:20. For the first time, a strong negative relationship between proportion of V8 sperm detected by molecular tools and C. capitata offspring was established. The models obtained should contribute to enhance the efficacy of SIT programs against this pest.

Three large saproxylic cerambycids with different pest/legal status co-occur in the Iberian oak woodlands, Cerambyx welensii (Cw), Cerambyx cerdo (Cc) and Prinobius myardi (Pm): Cw is an emerging pest, Cc is a protected but sometimes harmful species and Pm is a secondary/minor pest. A precise taxonomic diagnosis is necessary for research, management or protection purposes, but may be problematic mainly because Cw and Cc larvae are morphologically indistinguishable. To resolve this constraint, we genotyped adults, larvae and eggs collected over a wide geographical range using the mitochondrial barcoding of the cytochrome c oxidase subunit I (COI). A Neighbour-Joining tree phylogram revealed three distinct clusters corresponding to Cw, Cc and Pm. We further first sequenced for Cw and Cc two mitochondrial (12S rRNA and 16S rRNA) and one nuclear (28S rRNA) gene fragments. For the first two genes, interspecific divergence was lower than in COI, and for the 28S (lower mutation rate), the two species shared identical haplotypes. Two approaches for species delimitation (General Mixed Yule Coalescent (GMYC), Barcode Index Number (BIN)) confirmed the species distinctiveness of Cc and Cw. The Bayesian COI gene tree showed a remarkable genetic divergence between Cc populations from Iberia and the rest of Europe. Such divergence has relevant taxonomic connotations and stresses the importance of a wide geographical scale sampling for accurate DNA barcoding species identification. Incongruities between morphology/lineage and COI barcodes in some individuals revealed natural hybridization between Cw and Cc. Natural hybridization is important from a phylogenetic/evolutionary perspective in these cerambycids, but the prevalence of (and the behavioural/ecological factors involved in) interspecific cross-breeding remain to be investigated.

The egg parasitoid Telenomus podisi is a natural control agent of pentatomids, including Euschistus heros and Tibraca limbativentris, and success of parasitism is dependent upon the parasitoid finding the host. We tested the influence of host egg volatiles and the synthetic sex pheromone (zingiberenol) of T. limbativentris on chemotaxic behaviour of T. podisi, as well as, the impact of the original host on parasitoid selection. We used mated female T. podisi (48 h old) that emerged from the eggs of T. limbativentris or E. heros. The bioassays related to chemotaxy were performed in a Y-tube olfactometer and, to parasitism success, in laboratory and semi-field conditions. Telenomus podisi females that emerged from either the stink bug eggs, chose the pheromone more than control, or the pheromone plus eggs of E. heros in the semi-field bioassay, led to greater parasitism. Females that emerged from E. heros eggs chose egg volatiles from their original host rather than those from T. limbativentris, while females emerging from T. limbativentris, chose the egg volatiles of both hosts equally. When T. limbativentris was the original host, T. podisi females parasitized T. limbativentris over E. heros, while those emerging from E. heros exclusively parasitized E. heros eggs. These results demonstrated that T. podisi is more likely to parasitize the host in which it developed and that the original host can exert influence on the choice by those parasitoids. Understanding how the factors that mediate host–parasitoid communication are interrelated can help biological control programmes establish more effective and reliable tools with T. podisi.

The biology and economic status of aphids attacking rice throughout the world is reviewed, as is the literature concerning other aphids found in or near irrigated rice fields but not usually infesting rice. Altogether, 37 species of aphids belonging to seventeen genera are considered. The aphids are dealt with in two similar–sized groups according to their feeding sites, namely root–feeding and leaf–, stem– and ear–feeding species. Aphis craccivora Koch and Myzus persicae (Sulz.) are regarded as ‘occasional rice aphids’ as they are found on rice occasionally but do not regularly infest rice plants. A. gossypü Glov. is treated as a ‘rice aphid’ although its occurrence on rice plants is also sporadic. In addition to the literature survey, additional information is given based on field collections and observations, on the rice aphid component of more than 18 000 aphids trapped in yellow pan traps, on the natural enemies reared and collected and from laboratory experiments in Japan. Unpubished information was also extracted from the data labels of the British Museum (Natural History) aphid collection. The ecological relationships between rice aphids and aphids associated with weeds near irrigated rice fields in the Yamaguchi area of Japan is discussed. Three of the rice aphids were found on 22 species of weeds and the three ‘occasional rice aphids’ also occured on 22 species of weeds. A total of 43 species of weeds harboured aphids.

Cotesia urabae is a solitary larval endoparasitoid that was introduced into New Zealand in 2011 as a classical biological control agent against Uraba lugens. A detailed knowledge of its reproductive biology is required to optimize mass rearing efficiency. In this study, the courtship and mating behaviour of C. urabae is described and investigated from a series of experiments, conducted to understand the factors that influence male mating success. Cotesia urabae males exhibited a high attraction to virgin females but not mated females, whereas females showed no attraction to either virgin or mated males. Male mating success was highest in the presence of a male competitor. Also, the time to mate was shorter and copulation duration was longer when a male competitor was present. Larger male C. urabae had greater mating success than smaller males when paired together with a single female. This knowledge can now be utilized to improve mass rearing methods of C. urabae for the future.

Aphytis melinus DeBach was introduced to South Australia, reared in the laboratory, and then released against Aonidiella aurantii (Mask.) on citrus. In tests in nine citrus orchards, 100 adults of Aphytis melinus ensured colonisation during summer and early autumn, 1000 during late autumn, but even that number was insufficient during winter. Colonisation was equally successful whether Aonidiella aurantii was very abundant or very rare. The most efficient method for colonisation was therefore to release 100 adult parasites during summer and early autumn into small populations of A. aurantii. The parasite had dispersed at least three trees from each summer release site after five months, but much less following autumn releases. Ten months after summer release into nine trees of a total of 3330 adults, Aphytis melinus was recovered from 286 out of 354 (80%) trees in one orchard. In a further experiment, numbers of Aonidiella aurantii were reduced from 300–1000 per 150 leaves on five trees to less than 10 per 150 leaves 18 months after the release of Aphytis melinus, whereas on a control tree they increased from 550 to 1450 per 150 leaves over nine of those months.

In the course of some work at Rothamsted on the activity and abundance of insects, in which a light trap was used as a method of estimating the numbers of insects in a state of activity, it appeared advisable to have a further trapping method which did not depend on phototropic response for its efficiency. A rough design for a mechanical trap was therefore drawn up by the senior author.

The ecology of Microtermes subhyalinus Silvestri in savanna and an adjoining sugarcane plantation in the Central African Republic is described. Other species of termites were associated with savanna and sugarcane but M. subhyalinus was the most prevalent and the only one causing damage to sugarcane. Damage to the crop by M. subhyalinus was assessed throughout the year. Termite attacks were confined initially to the root system just after cutting but as the cane matured and growth ceased, termites tunnelled up into the above-ground stems. Losses accounted for 5–10% of total annual production. The nesting and foraging behaviour of this species altered with the change from natural savanna to sugarcane cultivation. The vertical distribution of M. subhyalinus fungus combs in soil under savanna and sugarcane over different seasons was analysed. There was a linear relationship between monthly rainfall and foraging activity in savanna while in sugarcane no relationship was observed.

The dubas bug, Ommatissus binotatus lybicus de Berg, is a serious pest of the date palm (Phoenix dactylifera) in Iraq, where there are two generations a year. Both nymphs and adults, which are described, suck the sap from the date palm. Repeated heavy infestations cause the weakening and death of some of the palms.

The eggs are laid on all the green parts of the palm except the fruits, the majority on the leaflets, especially the upper surface. They are distributed evenly on the four aspects of the date palms, but unevenly on the frond rows, the second and fourth oldest rows having the majority of the eggs in the overwintering and summer generations, respectively. Deposition of eggs of the overwintering generation began in the second week of November and hatching started during the first week of April, the nymphal period lasting 47 days and the adults surviving for 15 days. Eggs of the summer generation were deposited from the second week of June, and hatching started in the first week of August, the nymphal period lasting 50 days and the adults surviving for 13 days. There are five nymphal instars.

The nymphs excreted droplets of honeydew, and both nymphs and adults prefer the shady parts of the date palm. In order to escape the severe heat of the summer days, the nymphs and adults of the overwintering generation migrated towards the bases of the new fronds. The sex ratio was nearly 1:1, and the mean number of eggs laid per female was 106. The mortality rate for a constant population level was 98·11 per cent.

The eggs were parasitised by a small Chalcidoid. The larvae of the lace wing Chrysopa carnea Steph. and the adults of Coccinella septempunctata L., C. undecimpunctata L., and Chilocorus bipustulatus (L.) preyed upon the nymphs and adults.

In tests with inseeticidal sprays containing 240 g. active ingredient per 100 gal. applied at the rate of 1½ gal. per palm against adults and nymphs, DDT and malathion were equally effective, but Dipterex was less so. Similar concentrations of mixtures of malathion with heptachlor and DDT with diazinon were also effective.

Some of the problems involved in the estimation of parasitism in populations of Heliothis eggs are discussed:—

(a) Effective parasitism of the “active fraction” of eggs as laid in situ is denned.

(b) The habits of the egg-laying moth in point of the duration of oviposition on individual crops and diversion of moth activity from one host to another are discussed in relation to releases of Trichogramma lutea. Data are given on the distribution of bollworm eggs in a crop and associated factors.

(c) Investigations on the dispersion of liberated parasites are described. Dispersion was found to be rapid and widespread; concerted activity by large numbers in given areas did not apply.

Investigations in rain-grown crops are described and results are quoted from a typical experiment in maize, wherein the percentages of parasitism recorded in a large number of equal sections of the crop are regressed on proportionate larval survival. Although the egg parasitism ranged from 21·2 per cent, to 82·3 per cent., differences in larval populations were inappreciable. An explanation for this is offered in an analysis of the effect of various mortality factors.

The parasite was relatively ineffective in cotton crops. The low degrees of parasitism found are assigned to the growth-habit of the plant, the scattered manner of egg deposition thereon and the impediment offered to the insect by the dense hair processes of the plant at many sites where eggs are commonly placed.

Investigations on irrigated (cool season) market-garden crops and citrus orchards are described. These form the principal breeding sources of summer bollworm. Oviposition is extensive and sustained for three to four months on these crops, thereby affording opportunity for continuous parasite activity and the cumulative participation of progeny bred in the field. In nature Trichogramma lutea does not, however, appear until the latter end of the egg-laying by Heliothis and the authors were unable to establish laboratory-bred representatives at an earlier period.

Another egg parasite, Phanurus ullyetti, is prevalent before Trichogramma appears and accomplishes much that was hoped for from the attempted earlier introduction of Trichogramma. In effect, the latter, as seen from diagrams furnished with the paper, becomes substituted for Phanurus toward the close of the winter season. It is probable that temperature is a determining factor in the biology of both parasites, although other causes for the observed relations are suggested.

Further investigations are needed on the subject of exploiting T. lutea in the cool season.

To permit detailed study of individual tsetse, either as insects or as the vectors of trypanosomiasis, a method has been devised which resulted in excellent survival and reproduction when tested on females or Glossina austeni Newst.

Each mated female was maintained in asmall cage comprising a stainless steel frame covered with non-absorbent black Terylene netting through which the larvae and faeces fell into a tray. Each cage was applied daily to the ear of a rabbit, and records were kept of the number of feeds, time taken to feed, numbers of larvae produced, lengths of interlarvel periods and weights of pupae.

The following conclusions are tentative as they are based on detailed studies of only eight females. Five of these produced larvae regularly at 8½- to 9-day intervals. Ninety-six interlarval periods were investigated. Although the mean interval between meals was two days, the flies tended to fast before larviposition and to engorge repeatedly afterwards.

Among nearly regular breeders, failure to larviposit did not seem to interrupt the normal feeding rhythum: the reproductive rhythum later re-integrated with the feeding ehythum. A tendency to deviate from the normal feeding pattern either by too frequent feeding after larviposition or by prologation of the fasting period before larviposition, may possible be related to pemature death, but flies which tend to feed on the day before larviposition centainly risk death from pupation in utero—a condition found in 5 per cent. of dead rabbit-fed flies; the complex of pressures which lead to this condition is described.

Limited data suggest that females which live to a great age enter a post-productive period when about 6½ month old; the feeding pattern breaks down completely, the fly fasting for periods of up to 11 days, or even longer in the immediate pre-death period. The maximum output of reasonably sized pupae is probably about 20 for G. austeni.

Pupal weight increased until the parent flies were about 90 days old, but there was much individual variation; thereafter the weight remained high, but among very old dlies it fell towards the end of reproductive life. Certain individuals tended to produce heavy pupae, a characteristic probable associated with the size of the fly and the total weight of blood taken up in each interlarval period—not with the frequency of feeding; a very infrequent feeder may, however, produce underweight pupae at irregular intervals.

In 1935, Dr. Anderson made a sleeping sickness survey of the Kudaru District of Zaria Emirate, Northern Nigeria, where he found a high incidence of the disease. In the extreme case of the small hamlet of Sambo, he recorded a 70 per cent, infection rate among the 43 inhabitants.

The writer followed up this survey with an entomological investigation in the late dry season, and paid particular attention to. this hamlet.

The Varley & Gradwell method of population analysis is applied to data on populations of Saccharosydne saccharivora (Westw.), comprising 51 generations from 21 fields, obtained in Jamaica in 1961–62. Populations were estimated at five points in each generation, namely, maximum potential natality, and numbers of eggs laid, instar 1, peak instars 3–5, and of normal reproducing adults. Taking maximum potential natality as the first point in each life budget, graphical analysis showed that the key factor was mortality between instar 1 and reproducing adults or between peak instars 3–5 and reproducing adults. Reduced fecundity, due to submaximal leaf nitrogen, was density independent or possibly inversely density dependent; one egg parasite, Tetrastichus sp., was inversely density dependent while another, Anagrus flaveolus Waterh., and an undetermined egg mortality factor were density independent; parasitism of nymphs and presumably adults also by Stenocranophilus quadratus Pierce was density dependent, and was Considered to be the only regulating factor. The key factor was density independent, and it is concluded that, of the separate mortality factors contained within it, dispersal of adults is the most important. This itself depends on crop characters which could be altered by selective breeding or agricultural practice.

Leucopis argenticollis (Zetterstedt) and Leucopis piniperda (Malloch) are known to feed on the lineage of Adelges tsugae Annand that is native to western North America, but it is not known if they will survive on the lineage that was introduced from Japan to the eastern USA. In 2014, western Leucopis spp. larvae were brought to the laboratory and placed on A. tsugae collected in either Washington (North American A. tsugae lineage) or Connecticut (Japanese lineage). There were no significant differences in survival or developmental times between flies reared on the two different adelgid lineages. In 2015 and 2016, western Leucopis spp. adults were released at two different densities onto enclosed branches of A. tsugae infested eastern hemlock (Tsuga canadensis (L.) Carr.) in Tennessee and New York. Cages were recovered and their contents examined 4 weeks after release at each location. Leucopis spp. larvae and puparia of the F1 generation were recovered at both release locations and adults of the F1 generation were collected at the Tennessee location. The number of Leucopis spp. offspring collected increased with increasing adelgid density, but did not differ by the number of adult flies released. Flies recovered from cages and flies collected from the source colony were identified as L.argenticollis and L. piniperda using DNA barcoding. These results demonstrate that Leucopis spp. from the Pacific Northwest are capable of feeding and developing to the adult stage on A. tsugae in the eastern USA and they are able to tolerate environmental conditions during late spring and early summer at the southern and northern extent of the area invaded by A. tsugae in the eastern USA.

Tolerance of bioresmethrin, permethrin, deltamethrin and the natural pyrethrins with and without synergists (piperonyl butoxide and propyl prop-2-ynyl phenylphosphonate), and the frequency of kdr homozygotes (flies surviving a discriminating dose of DDT+FDMC (1,1-bis(4-chlorophenyl)-2,2,2-trifluoroethanol)) was investigated in 42 strains of Musca domestica L. collected on British pig farms and in one Canadian strain. Although all field strains were at least 4–10 times more tolerant of synthetic pyrethroids at the LD50 than the standard susceptible Cooper strain, and 27 strains (26 British + 1 Canadian) had detectable levels of kdr, pyrethroids failed to control flies on only nine farms where 10% of flies or more were homozygous for kdr and/or the LD50s (in μg/female) in bioassays equalled or exceeded 0·1 for bioresmethrin, 0·12 for permethrin, 0·012 for deltamethrin or 1·1 for pyrethrins. These figures correspond to resistance factors (Cooper strain = 1) of 20, 15, 30 and 4, respectively. Regression analyses showed a close relationship between the LD50s to pyrethroids and the frequency of kdr homozygotes. Cross-resistance to trichlorfon, which in part results in the 4–10-fold increased tolerance to pyrethroids observed in strains lacking kdr, was insufficient to cause control failure. The quantification of the relationship between the frequency of an insecticide-resistant genotype, levels of resistance as measured by bioassays and control failure in the field provides the means of forewarning when control failure is likely to occur and of confirming resistance as the cause when it has taken place.