Cotton stainers (Dysdercus spp.) are members of the family Pyrrhocoridae and many are pests of cotton throughout the tropics. Ten species are found in Africa (Pearson, 1958). Three of these have been established in colonies at Arusha, Tanzania. They are D. cardinalis Gerst., D. fasciatus Sign. and D. nigrofasciatus Stål.

This paper reports the results of a survey of parasitism of budmoths on larch in Europe as part of a programme to determine the potential of European parasitoids for the classical biological control of the North American defoliator, Zeiraphera canadensis Mutuura & Freeman. The parasitoid complexes of Zeiraphera diniana (Guenée), Exapate duratella (Heyden), Ptycholomoides aeriferanus (Herrich-Schäffer) and Spilonota laricana (Heinemann) are determined from field-collected samples of host larvae and pupae. The parasitoid complexes are characterized by their component guilds and the mean apparent parasitism of the individual species. Host phenology appears to affect the parasitoid complex of the larch budmoths. Parasitoids that attack the young larval instars are better represented from hosts that overwinter as larvae, while parasitism is dominated by the guilds that attack the late larval instars in hosts that overwinter as eggs. The study identifies the ichneumonids, Phytodietus spp., Chorinaeus cristator (Gravenhorst) and Phaeogenes osculator (Thunberg) for further experimental investigation as potential candidates for the biological control of Z. canadensis.

The number of male tobacco budworm, Heliothis virescens (Fabricius), trapped on a daily basis in pheromone traps in individual cotton fields was compared to male and female adult densities measured by nocturnal field sampling. The decline of trap efficiency with increasing female density was demonstrated. A simple relationship for estimating H. virescens male density from the numbers trapped was derived as P♂ = (E2/13)2, where P♂ is density and E2 is the two-day exponential average of number trapped. The standard error for the regression translates to an accuracy ratio of 2:1. The results compare favourably with previous research using mark-release-recapture methodology. Application of the formula is discussed.

Host shifts in herbivorous insects are thought to sometimes provide enemy-free space on the novel host plant. A population of the diamondback moth Plutella xylostella (Linnaeus), an oligophagous pest on crucifers, recently shifted to sugar snap- and snowpeas (Pisum sativum) in Kenya, resulting in heavy damage to these crops. The impact of this host shift on the interaction with Diadegma mollipla (Holmgren), one of the most frequent parasitoid species attacking P. xylostella in this area, was investigated. Parasitism rates and development of two strains of D. mollipla, one reared from a cabbage-feeding strain of P. xylostella and the second from the new pea-feeding strain, changed based on the host-plant that P. xylostella fed upon, with both parasitoid strains more effective on the novel host plant. Parasitism by the cabbage-D. mollipla strain on P. xylostella infesting peas was four times higher than on P. xylostella infesting cabbage when a single plant species was present. However, when both crops were offered together, the level of parasitism dropped to the level seen when cabbage was offered alone. Diadegma mollipla developed on both hosts, but cabbage-D. mollipla had a longer total development time. Pupae of cabbage-feeding P. xylostella were significantly heavier than pupae of pea-feeding P. xylostella and parasitism had no influence on these differences. Diadegma mollipla preferred to parasitize the pea-feeding P. xylostella. Thus, the host shift by P. xylostella to a novel host plant did not necessarily provide enemy-free space, with the parasitoid species tested. The implications of these findings for the host–parasitoid relationship are discussed.

Stored grain insect species in bulk-stored barley were sampled during 15 consecutive weeks in two ways: direct sampling based on grain trier samples and indirect sampling based on probe trap captures. A total number of 22 insect taxa were found; this study focused on the six most abundant species and their natural enemies. Four aspects were addressed: (i) differences in insect counts when based on either probe trap captures or grain trier samples, (ii) usefulness of grain temperature and moisture content as explanatory variables for insect densities, (iii) density-dependent relationships between natural enemies and their hosts, and (iv) spatial and non-spatial analyses of insect counts. Both total captures and frequencies of insect taxa were consistently higher in captures with probe traps than insect numbers obtained from grain samples. Regression analysis with abiotic conditions and probe trap captures as explanatory variables provided good fits to insect counts in grain samples for four of the six insect species (R2-values>0.40). Using multi-regression analyses, we showed that: (i) the occurrence of natural enemies was only weakly associated with the abundance of hosts; (ii) grain moisture content and temperature appeared to be at least as important variables as host availability; and (iii) the predictive strengths of regression models were similar when based on either data from grain samples or probe traps. Spatial analyses (SADIE) of both sampling data suggested that all data sets followed a spatially random distribution; re-arrangement of the data provided insight into important aspects of SADIE analyses of small data sets. Non-spatial analysis (Lloyd's aggregation index) showed significant differences among species and that the level of non-spatial aggregation was quite sensitive to sampling method used.

The effect of five photoperiods (0:24, 6:18; 12:12, 18:6, and 24:0 light:dark (L:D)) on the development, reproduction, and survival of the predatory thrips Scolothrips longicornis Priesner fed on the two-spotted spider mite, Tetranychus urticae Koch, was tested under laboratory conditions at 60% RH and 25°C. Development time of almost all immature stages in S. longicornis was the shortest under long day lengths (18:6 and 24:0 L:D). The adult duration of both sexes decreased with increasing light length from 6 to 24 h. The longevity of male and female decreased with increasing light length. Under a 12:12 L:D photoperiod, S. longicornis females had the longest oviposition period and longevity, highest net reproductive rate (R0 = 15.37), intrinsic rate of natural increase (r = 0.141), and finite rate of increase (λ = 1.151). Life table parameters showed a significant difference with various photoperiods. The consequences of the present research demonstrated that a 12:12 L:D photoperiod is the most favorable for the reproduction and development of S. longicornis fed on T. urticae, and that for mas rearing for augmentative biological control programs, would be the ideal photoperiod to maximize production.

Growth of the food fungus of the leaf-cutting ant Atta cephalotes (L.) on extracts of plants selected by the ants was shown to be affected by the plant species, the pH of the extract, the concentration of the sap or plant extract and pretreatment of the substrate by the ants. It was not possible to establish an unambiguous relationship between the rate of growth of the fungus on leaf extracts and the foraging preferences of the ants for the leaves. There were indications, however, that the fungus grows most rapidly on extracts of plant material preferred by A. cephalotes. Relative growth rates of the fungus on different substrates may be related to the presence of growth inhibitors rather than to nutrient availability.

With the exception of a short paper published some two and a half years ago by Major Patton, which, however, deals only with Tabanidae,* little or nothing has hitherto appeared in print on the subject of Mesopotamian representatives of the two families mentioned in the title of the present contribution. It is therefore hoped that the following notes, however incomplete, may be of some slight assistance to collectors of blood-sucking flies who may be stationed in Mesopotamia, and may at the same time stimulate them to further efforts.

The effects of soil-applied thionazin on field populations of Carabidae were assessed in two fields of potatoes in Berkshire, England. Broadcast at 11·2 or 44·8 kg/ha in a light sandy loam soil, thionazin considerably reduced numbers of Carabids for up to eight weeks after application. Lower catches occurred again six months later when treated soils were rotavated after lifting of the potato crop; these were attributed to the exposure of Carabidae to thionazin residues which had leached into deeper layers of the soil. Dosages of 2·24 or 8·96 kg/ha applied in rows sometimes increased numbers of Carabidae trapped, possibly because of sublethal effects increasing locomotor activity. Carabidae affected most by the treatments were the small diurnally active species such as Bembidion lampros (Hbst), B. quadrimaculatum (L.), and Trechus quadristriatus (Schr.) which were also abundant at the time when the treatments were applied. Larger species such as Harpalus rufipes (Deg.), Pterostichus vulgaris (L.), P. madidus (F.) and Calathus fuscipes (Goeze) were also affected but were generally less susceptible partly because they appeared later in the season when the pesticide had partly disappeared. The rapid disappearance of thionazin from the surface 1·3 cm of soil could account for the low susceptibilities of non-burrowing species; Asaphidion flavipes (L.) which rarely burrowed was less susceptible and Harpalus aeneus (F.) which readily burrowed was more susceptible than other species of similar size.

Spodoptera frugiperda (J.E. Smith) is a major pest in maize fields in Argentina. However, a sampling method that accounts for spatial pattern and allows reliable pest density estimations is still lacking. This paper addresses the issue of how sampling unit size can influence the characterization of S. frugiperda spatial pattern and the performance of sampling plans. An intensive sampling programme for S. frugiperda larvae was carried out in maize fields from October until March in four growing seasons. On each sampling date, 12 to 20 sampling units were taken at random. Each unit consisted of 1, 2, 4, 6, 8, 10 or 12 consecutive plants along a row. The linearized version of the Taylor's power law (TPL) was fitted to mean and variance estimated for each sampling date and data set through least squares regression. In general, b values from TPL were significantly >1 (P<0.05), indicating an aggregated sampling distribution. Regression slopes (b) ranged from 1.28 to 1.48 in small larvae and from 1.06 to 1.24 in large larvae, indicating stronger clumping in the former. TPL parameters were used to develop constant precision sampling plans. The efficiency of these plans in terms of expected total cost (searching and handling sampling units) was very sensitive to the size of the sampling units with small larvae but not with large larvae. The influence of sampling unit size and spatial pattern on TPL parameters and sampling costs is discussed.

The fourth stage larvae of A. superpictus, sergenti, funestus and aconitus are discussed. A. superpictus may be at once separated from the others by the absence of float-hairs, or rudiments of float-hairs, from the metathorax and first abdominal segment; also by the small extent of the dark markings on the head, and the narrowness of the dorsal plates of the abdomen. A. sergenti differs from A.aconitus and funestus (of which Edwards has suggested that it might be regarded as a variety) principally in the abdominal plates. A. aconitus and A. funestus differ from one another in details connected with the inner anterior clypeal (i.a.) pre-antennal (pr.a.) and vertical (v.) hairs, and in the shape of the abdominal plates, but they are evidently closely related, if larval anatomy is any evidence of relationship.

Our present day lack of knowledge of the physical factors involved in the selection of breeding-places by certain types of mosquitos is to be deplored. Just why certain species choose particular types of water for their oviposition is a matter about which there is much conjecture, but it is hoped that in the near future some light may be thrown upon this subject by taking into consideration various aspects of the question hitherto uninvestigated.

The galleries of the bark-beetles are as a rule such characteristic features of the different species that sometimes these are more easily recognised by the shape of their galleries than by their own structure, as, for example, in the case of the two pine-beetles, Blastophagus piniperda and B. minor, in which the distinguishing features of the insects cannot be discerned without the help of a good pocket-lens. But, on the other hand, the galleries of many species are subject to a certain amount of variation and show typical modifications which are responses to various external factors, such as the size of the trunk or of the branches, the thickness of the bark, and the orientation of the trunk, viz., whether the tree is standing or felled.

The E2F transcription factor family is distributed widely in eukaryotes and has been well studied among mammals. In the present study, the E2F transcription factor 4 (E2F4) gene was isolated from fat bodies of Antheraea pernyi and sequenced. E2F4 comprised a 795 bp open reading frame encoding a deduced amino acid sequence of 264 amino acid residues. The recombinant protein was expressed in Escherichia coli (Transetta DE3), and anti-E2F4 antibodies were prepared. The deduced amino acid sequence displayed significant homology to an E2F4-like protein from Bombyx mori L. Quantitative real-time polymerase chain reaction analysis revealed that E2F4 expression was highest in the integument, followed by the fat body, silk glands, and haemocytes. The expression of E2F4 was upregulated in larvae challenged by bacterial (Escherichia coli, Micrococcus luteus), viral (nuclear polyhedrosis virus), and fungal (Beauveria bassiana) pathogens. These observations indicated that E2F4 is an inducible protein in the immune response of A. pernyi and probably in other insects.

The following are some new species of Aphididae found in Africa. The majority are from the collection sent me by Mr. F. C. Willcocks, Entomologist to the Sultanic Agricultural Society of Egypt. Others have been received by the Imperial Bureau of Entomology.

Four previously described species are added, so as to keep these lists complete:—

1. Macrosiphum dahliafolii, nov. sp.

2. Aphis durantae, sp. nov.

3. Aphis zizyphi, sp. nov.

4. Aphis ficus, sp. nov.

5. Aphis tamaricis, sp. nov.

A diet previously described for rearing Pieris brassicae (L.) was found to be very successful for rearing Mamestra brassicae (L.). Less than 5 per cent. of the pupae that formed entered diapause. The larvae can be much more quickly counted, examined and looked after when kept on the diet than when kept on cabbage leaves.

The specialist tingid, Carvalhotingis visenda, is a biological control agent for cat's claw creeper, Macfadyena unguis-cati (Bignoniaceae). Cat's claw creeper is an invasive liana with a wide climatic tolerance, and for biological control to be effective the tingid must survive and develop over a range of temperatures. We evaluated the effect of constant temperatures (0–45°C) on the survival and development of C. visenda. Adults showed tolerance for wider temperature ranges (0–45°C), but oviposition, egg hatching and nymphal development were all affected by both high (>30°C) and low (<20°C) temperatures. Temperatures between 20°C and 30°C are the most favourable for adult survival, oviposition, egg hatching and nymphal development. The ability of adults and nymphs to survive for a few days at high (40°C and 45°C) and low (0°C and 5°C) temperatures suggest that extreme temperature events, which usually occur for short durations (hours) in cat's claw creeper infested regions in Queensland and New South Wales states are not likely to affect the tingid population. The potential number of generations (egg to adult) the tingid can complete in a year in Australia ranged from three to eight, with more generations in Queensland than in New South Wales.

The willow sawfly, Nematus oligospilus (Förster), is a pest in Salix commercial forests and has been reported worldwide. Female adults must recognize a suitable host plant to oviposit, since her offspring lack the ability to move to another host. We evaluated the effect of conspecific herbivory on the oviposition choices of N. oligospilus females by providing damaged (DP) and undamaged (UP) plants of Salix humboldtiana, a native willow from South America, as oviposition substrates. Local and systemic effects were studied. For the local treatment, a twig from the DP with damaged leaves was contrasted to a twig from a UP in dual choice experiments. For systemic treatment, a twig from the DP with intact leaves was contrasted to a twig from a UP. We estimated the use of olfactory and contact cues by comparing volatile emission of DP and UP, and by analysing the behaviour of the females during host recognition after landing on the leaf surface. In the context of the preference–performance hypothesis (PPH), we also tested if oviposition site selection maximizes offspring fitness by evaluating neonate hatching, larval performance and survival of larvae that were born and bred on either DP or UP. Our results demonstrate that previous conspecific herbivory on S. humboldtiana has a dramatic impact on female oviposition choices and offspring performance of the sawfly N. oligospilus. Females showed a marked preference for laying eggs on UP of S. humboldtiana. This preference was found for both local and systemic treatments. Volatile emission was quantitatively changed after conspecific damage suggesting that it could be related to N. oligospilus avoidance. In the dual choice preference experiments, the analysis of the behaviour of the females once landing on the leaf surface suggested the use of contact cues triggering egg laying on leaves from UP and avoidance of leaves from DP. Furthermore, 48 h of previous conspecific feeding was sufficient to dramatically impair neonate hatching, as well as larval development and survival, suggesting a rapid and effective reaction of the induced resistance mechanisms of the tree. In agreement with the PPH, these results support the idea that decisions made by colonizing females may result in optimal outcomes for their offspring in a barely studied insect model, and also opens the opportunity for studying tree-induced defences in the unexplored South American willow S. humboldtiana.

Resistance of cocoa to Planococcoides njalensis (Laing) was assessed in the laboratory in Ghana by rearing the mealybug from birth until death on seven cocoa progenies, and determining survivorship, duration of reproduction, gross reproductive rate and live weight. Field evaluation was by sampling both P. njalensis and Planococcus citri (Risso) on the tree trunks and in terminal buds. Progenies 85D/176A × M7/537 and T12/116 × T62/977 were judged the most resistant using the parameters determined in the laboratory. The resistance factor is attributed to antibiosis. The mealybug populations in the field did not show any significant differences among the progenies, but the trend followed the laboratory results. It is suggested that the laboratory method reported here is adequate in assessing resistance, has the advantage of being faster than the field technique and can be used in combination with existing methods for assessing cocoa progenies for resistance to the virus disease.