The corn leafhopper Dalbulus maidis (Hemiptera: Cicadellidae), a specialist herbivore, is the cause of serious losses in maize yield for its capacity to transmit three important plant pathogens. They are also active phloem feeders, that insert stylets into the plant as they feed. Females place their eggs endophytically, totally inserted in the central midrib or the leaf blades, leaving conspicuous openings in the place where the ovipositor was inserted. In spite of the consequences that feeding and oviposition may have on the water status of the plant and the production of biomass, direct damage caused by the leafhopper has been only scarcely studied. In the present contribution, we measured biomass loss due to direct damage in maize plants under two watering regimes, with water supply ad libitum and with a watering restricted regime, emulating the most frequent field conditions. Moreover, we analyzed the effects of increasing densities of the vector on the biomass loss and plant mortality and the effects of females vs males. We observed that a density of 10 insects is sufficient to cause damage to 10-day-old seedlings, even in an ad libitum watering regime; however, in drought conditions, damage can be significantly greater, causing plant mortality. Also, females cause more damage than males, due to their oviposition habits.

Among the large family of the Eulophidae (Chalcidoidea), the Euplectrini are closely related to the Elachertini and form with them the subfamily Elachertinae. In common with the genus Elachertus, Spin., they have antennae with a 4-jointed funicle, complete parapsidal furrows, often longitudinal furrows on the scutellum and a petiolated abdomen. They are, however, easily distinguished by the large size of the spurs of the hind tibiae, the longest being generally more or less as long as the first two tarsal joints together.

The seasonal incidence curve of strike is bimodal, and divisible into four phases, the pre-shearing, the shearing trough, the lamb phase, and the late season adult and lamb phase. About two-thirds of the strikes reported by shepherds occurred in the hindquarters area (this term including the rump and hindlegs). In a lowland flock where all strikes were noted over a five-year period the incidence of hindquarters strikes was much lower (43 per cent.). The shoulders area, in relation to its size, is highly susceptible. It appears to be even more common a site in lowland than in mountain breeds. Rather more than half of the reported cases were in adult sheep, and of these more than half were in shorn sheep. Body strikes were relatively more common in shorn than in woolled sheep. Species other than L. sericata (referred to as alternative species) occurred mainly in mountain breeds or their lowland crosses, and more frequently in body than in breech strikes. Alternative species were more or less equally common in adults and in lambs, except Phormia terraenovae, which was practically confined to adults. The occurrence of alternative species was significantly associated with the type of grazing, and also with the vegetation type on the grazing ; the partial association with vegetation type, with pasture type constant, suggests that presence of bracken and/or heather is closely associated with the conditions resulting in alternative species striking sheep.

Control of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), populations or outbreaks may be achieved through the mass-rearing and inundative release of sterile B. tryoni. An alternative release method is to release chilled adult sterile fruit flies to decrease packaging and transport requirements and potentially improve release efficiencies. Two trials were conducted to determine the effect of chilling on the performance of two separate batches of adult B. tryoni, fed either a protein and sucrose diet or sucrose only diet. The first trial compared chill times of 0, 0.5, 2 and 4 h; the second trial compared chill times of 0, 2, 4, 8 and 24 h. Overall, there was little or no affect of chilling on the recovery, longevity and flight ability of B. tryoni chilled at 4°C. Recovery time can take up to 15 min for chilled adult flies. There was no effect of chill time on longevity although females generally had greater longevity on either diet compared with males. Propensity for flight was not adversely affected by chilling at the lower chill times in trial 1; however, in trial 2, adults fed on a protein and sucrose diet had a decreased tendency for flight as the chilling time increased. Fly body size did not affect recovery times although the smaller adult B. tryoni in trial 1 had significantly reduced longevity compared to the larger adults in trial 2. Implications of these findings for B. tryoni SIT are discussed.

Cylindropuntia fulgida (Engelmann) F.M. Knuth var. fulgida (Engelmann) F.M. Knuth (Cff) (Caryophyllales: Cactaceae) is native to Mexico and Arizona and was introduced into South Africa for ornamental purposes. It subsequently became highly invasive, necessitating control. The cochineal insect, Dactylopius tomentosus (Lamarck) (Hemiptera: Dactylopiidae), was selected as a potential biological control agent based on its restricted host range among Cylindropuntia species and previous success in controlling C. imbricata (DC.) F. Knuth (Ci). Eight D. tomentosus provenances (Cholla, Cholla E, Fulgida, Mamillata, Imbricata, Tunicata U, Tunicata V and Rosea) from Cylindropuntia species in their native ranges were reared on Cff, whilst Cholla and Imbricata were also reared on Ci. Large differences were found in the development and survival of crawlers, and in the reproductive capacity of females. Three subjective categories of provenance interaction with host plants were identified based on a fitness index (FI) calculated from data relating to crawler survival, female development time and fecundity: (i) thriving (FI≥1) – insects had shorter developmental times, high crawler survival and highly fecund females (Cholla); (ii) surviving (FI<1 but >0) – insects had extended development times, low crawler survival and low fecundity (Imbricata, Fulgida and Mamillata); and (iii) dying (FI=0) – insects died before or at the second instar (Rosea, Tunicata U and Tunicata V). Cholla, therefore, is highly suitable for biological control of Cff in South Africa. In addition, Cholla thrived on Cff but only survived on Ci whilst, in contrast, Imbricata thrived on Ci but only survived on Cff. This differential ability of provenances to thrive or survive on different host plants demonstrated that host adapted biotypes of D. tomentosus exist; therefore, biotypes should be taken into account when considering this species as a biological control agent of cactus weeds.

Between 1925 and 1947, 9,929 samples of bees from Great Britain were examined for acarine and Nosema diseases. There was a significantly lower incidence of acarine disease in English samples than in Scottish ones, but a somewhat higher incidence of Nosema disease in England than in Scotland was not significant. A decrease in the incidence of acarine disease over the 22 years was highly significant in both England and Scotland, although the rate of decrease was not significantly different between the two countries.

The average incidence of acarine disease during each month of the year was at its lowest in April, May and June, while Nosema disease reached its maximum in these three months and fell to a minimum in the autumn. Data on the seasonal incidence of Nosema disease in an apiary in Scotland between 1948 and 1953 show a similar distribution to that for Great Britain. Eesults on the incidence of both diseases throughout the year are compared with those of other authors, and possible reasons for the seasonal fluctuations are discussed.

A description is given of the bionomics of Leucoptera caffeina Wshbn. in the Kilimanjaro District, Tanganyika, and of the characters that distinguish it in its various stages from L. coffeella (Guér.), together with the results of population studies of the former insect and its parasites in both shaded and unshaded coffee in 1938–40.

During the 1939 outbreak, the numbers of eggs per tree, and the number of live pupae present in samples of about 100 cocoons (estimated from te number of moths and parasites emerging) showed large fluctuations. The times between peak numbers approximated to the total life-cycle, indicating that at any moment one developmental stage was dominant.

Previous studies have shown that the aphid species, Aphis fabae Scopoli and Megoura viciae Buckton, do not produce winged offspring in the presence of natural enemies, in contrast to results for the pea aphid (Acyrthosiphon pisum (Harris)) and the cotton aphid (Aphis gossypii Glover); but these studies did not involve exposing aphids directly to natural enemies. We exposed colonies of both A. fabae and M. viciae to foraging lacewing (Chrysoperla carnea (Stephens)) larvae and found that the predators did not induce winged morphs among offspring compared to unexposed controls. Colonies of A. fabae responded to an increase in aphid density with increasing winged morph production, while such response was not found for M. viciae. We suggest that different aphid species differ in their susceptibility to natural enemy attack, as well as in their sensitivity to contact.

Native insects can become epidemic pests in agro-ecosystems. A population genetics approach was applied to analyze the emergence and spread of outbreak populations of native insect species. Outbreaks of the mirid bug, Stenotus rubrovittatus, have rapidly expanded over Japan within the last two decades. To characterize the outbreak dynamics of this species, the genetic structure of local populations was assessed using polymorphisms of the mtDNA COI gene and six microsatellite loci. Results of the population genetic analysis suggested that S. rubrovittatus populations throughout Japan were genetically isolated by geographic distance and separated into three genetic clusters occupying spatially segregated regions. Phylogeographic analysis indicated that the genetic structure of S. rubrovittatus reflected post-glacial colonization. Early outbreaks of S. rubrovittatus in the 1980s occurred independently of genetically isolated populations. The genetic structure of the populations did not fit the pattern of an outbreak expansion, and therefore the data did not support the hypothesis that extensive outbreaks were caused by the dispersal of specific pestiferous populations. Rather, the historical genetic structure prior to the outbreaks was maintained throughout the increase in abundance of the mirid bug. Our study indicated that changes in the agro-environment induced multiple outbreaks of native pest populations. This implies that, given suitable environmental conditions, local populations may have the potential to outbreak even without invasion of populations from other environmentally degraded areas.

Gene diversity and gene flow in Glossina pallidipes Austen were studied by using allozyme electrophoresis on samples from southern and East Africa. Recorded were 30 alleles segregating at eight loci. Gene diversity was 0.212±0.085 S.E. in four southern African populations and 0.163±0.076 in seven Kenyan populations. All loci were in Hardy-Weinberg equilibrium. Pgm and 6pgd were sex linked. Spatial components of gene diversity were measured by using F statistics. Mating was random within each population. The ‘fixation index’ FST was 0.133±0.062 among southern African populations. Among the Kenyan populations. FST was 0.159±0.069. FST was 0.238±0.051 among all populations. Analysis of variance of gene frequencies showed that 65.8% of the genetic variance lay within populations and 34.2% of the genetic variance lay between Kenyan and southern African populations. These data suggest a strong measure of genetic drift among tsetse populations even in a region where it is thought they are continuously distributed. The causes of this drift require investigation.

The Epilachninae constitute one-sixth of the known species of the family Coccinellidae. They are herbivorous and include a number of well known pests of cultivated plants in different parts of the world. Their adults present a great uniformity of external structure, with the result that nearly all the known species have been placed in one genus, Epilachna Hope. Their identification is made more difficult by the employment of characters such as the elytral markings and spots which may vary a great deal in one species or be almost identical in two quite unrelated species. Lately, there has been a tendency to split the genus by employing more reliable morphological characters, including genitalia. A greater knowledge of the biology and morphology, including that of the immature stages, particularly the larvae, is necessary to evolve a natural classification. Relatively little was known of the larvae. This paper deals with 14 species belonging to six different genera.

In addition to discussion of the relationship of this subfamily with other Coccinellidae in the light of the extensive larval material examined, it is observed that larvae belonging to different genera, including those recently erected or revived, show considerable morphological differences that support a division of Epilachna (s.l.) based on adult characters. A study of the larvae of nine species that are still retained in the genus Epilachna shows that they are separable into several groups, which may well indicate where further division of the genus may be made.

Two experiments were conducted to determine Chilo partellus (Swinhoe) moth and larval response on sorghum lines differing in levels of antibiosis and antixenosis. The inbred lines were E 302, IS 2205, IS 2122 and SA 2681, all reportedly varying in levels of antibiosis and ovipositional and larval antixenosis to C. partellus. Ovipositional antixenosis was evaluated in choice tests under cage conditions and significant differences were observed in the average number of egg batches per line. E 302 received the greatest number of egg batches. Antibiosis and larval antixenosis was evaluated with artificial infestation in a greenhouse. Significant differences occurred in larval numbers and mean larval mass on different lines, with E 302 possessing the greatest level of antibiosis resistance. This study indicates that resistant genotypes such as E 302 may exhibit high levels of antibiosis or larval antixenosis, but may also be preferred for oviposition. The size of egg batches was not influenced by ovipositional antixenosis. The potential effect of ovipositional antixenosis mechanisms on pest populations under field conditions is discussed.

Gyranusoidea tebygi sp. n., an encyrtid parasitoid of Rastrococcus on mango in India, is described and compared with related species. The parasitoid is to be introduced into West Africa in an attempt to control the mealybug, which is a serious pest of mango and citrus in some West African countries.

The causes of fluctuation and stabilisation in a population of Andraca bipunctata Wlk. on tea in India were assessed over three years using the technique of key-factor analysis. Failure to produce the maximum complement of eggs, together with female mortality and adult migration, is shown to be the key-factor. Other mortality factors include non-viability of eggs and parasitism of the caterpillars by the tachinid Cylindromyia sp. Mortality of the female pupae tends to stabilise the population by compensating for losses due to the key-factor, but neither this nor any other mortality factors appear to be significantly density-dependent. The need for devising specialised sampling procedures and statistical tests for tropical insect populations is discussed.

Populations of Nysius vinitor Bergroth were studied from 1979 to 1982 in two weed hosts, Arctotheca calendula and Polygonum aviculare, and eight irrigated sunflower crops in a summer cropping area of northern Victoria, Australia. The spring generation began with the adults colonizing flowering A.calendula plants in September and concluded with the rapid development of late stage nymphs and an exodus of adults from these plants from mid-November to December. Gradual invasion of sunflowers occurred mostly in late December and reached a peak at flowering, after which nymphs appeared. P. aviculare attracted adults from February and hosted a number of overlapping generations until winter. The weed sustained diminishing numbers of adults through the winter, except in 1982, when a further generation produced an early spring peak. Immigrant populations were regarded as a common source of adults for initiating the spring and summer generations. The rate of development of N. vinitor in spring was more rapid than that predicted by phenological simulation based on ambient temperatures and laboratory-derived day-degree estimates. This was attributed to increased body temperatures through absorption of solar radiation, and the simulation model was adjusted by increasing daily minimum and maximum temperatures by 1·3 and 5·5°C for young and older instars, respectively. This suggested that older nymphs have lower developmental thresholds or are better able to optimize body temperatures.

Pelidnoptera nigripennis (F.) is a parasitoid of the millipedes Ommatoiulus spp. in Portugal. It is univoltine. The adults lay eggs on their hosts during the spring in southern Portugal, and the first-instar larva penetrates through the soft tissue of the millipede. The parasitoid spends the summer as a firstinstar larva, kills the host during the autumn when in the third instar and overwinters in the pupal stage. P. nigripennis occurs in habitats of low bushes, but not in open grasslands. The female searches for prey by day. The maximum rate of parasitism recorded in this study was 20%. In laboratory specificity studies, 15 species of millipedes from five families were exposed to P. nigripennis, but only julid millipedes were successfully parasitized. Synchronization of the life-cycle in the laboratory with the seasons of the southern hemisphere was achieved by inducing pupation five months prematurely after cooling to 10°C.

Four designs of trap, all made from identical material, were compared at Galana Ranch, south-eastern Kenya, as sampling devices for Glossina pallidipes Austen and G. longipennis Corti. The NG2G and Epsilon traps caught more than twice as many female G. pallidipes as the biconical trap, and the F3 was intermediate. A similar, pattern was observed for males, although the differences were smaller, and not significant. The NG2G, Epsilon and F3 traps all caught approximately twice as many male and female G. longipennis as the biconical trap. Acetone (500 mg/h) significantly increased trap catches of G. pallidipes, and there was a synergism between acetone and 4-methylphenol (0.8 mg/h). There was little or no effect with 1-octen-3-ol (0.8 mg/h). Acetone, 1-octen-3-ol, and 4-methylphenol all increased trap catches of G. longipennis, and there were no synergisms among them. Cow urine (850 mg/h) increased the catches of both species in traps baited with acetone and 1-octen-3-ol, although not significantly for G. longipennis. There was no effect with 3-methylphenol (0.8 mg/h). The addition of 3-propylphenol to traps baited with acetone, 1-octen-3-ol and 4-methylphenol had no effect on the catches of either species. For G.pallidipes, a combination of acetone, 1-octen-3-ol, 4-methylphenol and 3-propylphenol was calculated to have a catch index of 6–8 over unbaited traps, a value lower than that reported for Zimbabwe and Nguruman, Kenya, and greater than that reported for Somalia. The catches of G. longipennis were approximately three times higher on electrified targets than in F3 traps, although there was no difference in the catch of G. pallidipes.

Low fecundity in the laboratory was found in populations of Aedes aegypti (L.) exhibiting Black tergite (Bt), a phenotype characteristic of the feral A. a. formosus (Wlk), whereas high fecundity was found in six domestic populations of A. a. aegyptiin which the phenotype was absent. An investigation of the cause of low oviposition by the feral population indicated that behavioural differences in mating and feeding were not responsible; egg retention was identified as the major factor. Introduction into laboratory procedure of a variable simulating the feral environment, i.e., coconut-shell infusion at the oviposition site, induced a highly significant increase in feral fecundity both through its chemical constituents and visual attraction. Differential response to oviposition site is discussed in relation to the evolution of subspecies of A. aegypti.

Aulacaspis tegalensis (Zhnt.) (Diaspididae) infests the stems, and to a lesser extent the leaves, of sugar-cane. It is indigenous to Malaya and the islands of S.E. Asia, and has been introduced to the Mascarene Islands and East Africa. Its biology and economic importance were studied in Mauritius. Development and construction of the scale in both sexes are described. The life cycle takes 3–9 weeks, the female laying 700–800 eggs over 10 weeks in summer and 14 in winter. Feeding in the stem is in the parenchyma; the path of the stylet is intracellular and vascular bundles are avoided. Stem surfaces are essential for population increase. The leaf sheaths which invest stems tightly or loosely according to their age, have a decisive role among factors that influence intensity and pattern of stem infestation. Field infestations may be severe in dry coastal areas. Populations increase in March-May, and decline in July-November. The determining factors are seasonal weather, crop growth, harvesting and natural enemies. Dispersal, by the eggs and crawlers, is passive. Adelencyrtus miyarai Tachikawa (Encyrtidae) is constantly associated with Aulacaspis tegalensis and is heavily hyperparasitised by Tetrastichus sp. (Eulophidae). The most frequent predators are Lindorus lophanthae (Blaisd.) (Coccinellidae), Cybocephalus mollis Endrödy-Younga (Nitidulidae) and mites. Predators are important only in the regulation of large A. tegalensis populations. Reductions in the sucrose content of the cane juice are directly proportional to the numbers of scales present on each interaode; growth of canes is not obviously affected, but grown canes may die before harvest. Reduced germination and growth may result from use of infested propagative material. Practicable control measures comprise use of clean or hot-water-treated propagative material, field hygiene and block harvesting, removal of dry leaves to expose the stems, and varying the date of harvest.

The colour change and formation of green pigment in Mantis, Acrida, Locusta, Schistocerca and Dixippus are studied.

There is no background reaction to green and brown or yellow colour in these species.Usually the young nymphs of Mantis are green; some ofthe old nymphs and adults have a tendency to lose the green pigment. Phytophagous nymphsbecome green only when fed on fresh or growing grass. Green individuals may be obtained in darkness on this food (Locusta). The green pigmentdisappears on a diet of dry grass.

The colour change from non-green to green, or vice versa, is dependent on the formation or disappearance of the blue component (bile pigment-protein) of green pigment. The blue pigment generally appears first in the blood and is deposited in the integument at the following moult; it does not appear to be a breakdown product of chlorophyll or haematin. It is probably synthesised from a colourless precursor in the peripheral fat body.

Observations made on the pericardial cells of Locusta suggest that the blue pigment may be converted into insectorubin.