International Journal of Insect Science

Since the first detection of Bactrocera dorsalis in Botswana in 2010, the establishment, spread, and response to prevailing Botswana microclimates under rapidly changing environments remain unknown. This study investigated the presence, seasonal population abundance, and thermal biology of B. dorsalis in Botswana. We measured B. dorsalis thermal tolerance vis critical thermal limits (CTLs) and lethal temperature assays (LTAs) to understand how temperature largely impacts on fitness and hence invasive potential. Seasonal monitoring results indicated B. dorsalis establishment in the Chobe district (its first area of detection). Trap catches showed continuous adult flies’ presence all year round and high average monthly trap catches as compared with other districts. Furthermore, B. dorsalis was detected south of Botswana, including Kgatleng, Kweneng, South-east, and Southern districts. Critical thermal maxima (CT_max) to activity for adults and larvae were 46.16°C and 45.23°C, whereas critical thermal minima (CT_min) to activity for adults and larvae were 9.1°C and 7.3°C, respectively. Moreover, we found an improved CT_min for larvae at a slower ramping rate, indicating potential rapid cold hardening. The lower lethal temperature (LLT) and upper lethal temperature (ULT) assays revealed a reduction in survival at all the developmental stages as severity and duration of both temperature extremes increased. Microclimatic temperatures recorded in Botswana showed that environmental temperatures fall within the thermal breath of B. dorsalis activity measured here, indicating a potential conducive climate niche for the insect pest across the country, albeit other factors, e.g., host availability, play a significant role. These results therefore suggest that Botswana microclimatic temperatures aided B. dorsalis activity and invasion pathway are thus significant in mapping invasions and pest risk analysis, and may also aid in designing pest management strategies.

Three communities along Badagry axis of the Lagos lagoon were sampled for indoor resting Anopheles mosquitoes in order to determine their species composition, relative abundance, density and contribution to malaria transmission in the coastal ecosystem. A total of 1938 adult female Anopheles mosquitoes collected from 2005 to 2007 constituted three species viz Anopheles gambiae, An melas and An. nili. The Polymerase Chain Reaction (PCR)–-based tests indicated that more than three-fourth of the An. gambiae s.l (75.8%) population belongs to An. gambiae s.s the remaining were An. melas. Further analysis showed that all the An. gambiae s.s was the M form. ELISA-based analyses indicated that An. gambiae s.s and An. melas were the main vectors of malaria in this area with an overall P. falciparum sporozoite infection rate of 4.8% and 6.5% respectively. Both species also maintained relatively high EIR indicating their prominent roles in malaria transmission in the study area. All the An. nili tested were negative for P. falciparum sporozoite infection. This study provides baseline information for planning vector control programme relevant to reduction of malaria transmission in the coastal areas of Nigeria.

In this study, we investigated the population growth of the Liposcelis yunnaniensis (Psocoptera: Liposcelididae) feeding on ten different diets. Out of the ten diets, eight were made of plain cereals namely wheat (Triticum aestivum L.), corn (Zea mays L.), barley (Hordeum vulgar L.), oats (Avena sativa L.), rice (Oryza sative L.), and sorghum (Sorghum bicolour L.) while two were the artificial diets named Nayak wheat diet and Universal diet. The population growth was recorded as corn > wheat > universal diet > hulled barley > rice (hulls intact) > barley (hulls intact) > sorghum > Nayak wheat diet > oats > hulled rice. After 32 d culture, the initial 5 psocids developed to the populations as 41.8 ± 4.26, 41.5 ± 4.09 and 39.1 ± 7.64 on corn, wheat and universal diet, respectively. Meanwhile, psocids feeding on Nayak wheat diet, oats and hulled rice had significantly lower populations with 25.6 ± 2.42, 22.5 ± 3.09 and 13.6 ± 2.36 respectively. Rice and barley were included in the diets with and without hulls to see their effect on population growth. In case of barley, hulls had no significant effect on population growth while rice with hulls had significantly higher populations than rice alone. This study has confirmed the relative level of suitability of different cereals for this species when damaged. We have described a method to get the uniform age adults that can be helpful in research experiments.

Iron overload in the fortified flour can influence the life stages and physiology of the insects. The present study was carried out to evaluate the effect of commercially available premix iron fortified flour as well as effect of different concentrations of post-mix iron fortified flour (30–5 ppm) on biology of red flour beetle, Tribolium castaneum (Hebrst.). Larval and pupal duration, total developmental time, fecundity and larval weights in two consecutive generations of beetle were compared with control treatment. Amylase and protease activities of gut of the beetle were also measured in premix and postmix flours.

Results showed that larval mortality increased in two sources of premix iron flour when compared with control. Larval weight was reduced in first generation only. The larval mortality was significantly higher in 30 ppm postmix iron fortified flour than in other postmix concentrations and control treatment. The larvae of T. castaneum fed on two sources of premix and in various concentrations of postmix iron fortified flour revealed an increase in amylases and decrease in protease activities.

Although the movement of stable fly, Stomoxys calcitrans (L.), has been studied, its extent and significance has been uncertain. On a local scale (<13 km), fly movement occurs between host animals and resting sites to feed and mate, mainly at on-farm locations where herbivorous livestock regularly congregate. Small numbers emigrate from livestock congregation sites in search of other hosts and oviposition substrate, mostly within <1.6 km. Such local movement occurs by flight ∼90 cm above ground, or with moving livestock. While stable flies are active year-round in warm latitudes, cold winters in temperate areas result in substantial population and activity declines, limiting movement of any sort to warmer seasons. Long-distance dispersal (>13 km) is mainly wind-driven by weather fronts that carry stable flies from inland farm areas for up to 225 km to beaches of northwestern Florida and Lake Superior. Stable flies can reproduce for a short time each year in washed-up sea grass, but the beaches are not conducive to establishment. Such movement is passive and does not appear to be advantageous to stable fly's survival. On a regional scale, stable flies exhibit little genetic differentiation, and on the global scale, while there might be more than one “lineage”, the species is nevertheless considered to be panmictic. Population expansion across much of the globe likely occurred from the late Pleistocene to the early Holocene in association with the spread of domesticated nomad livestock and particularly with more sedentary, penned livestock.

The efficacy of Bacillus thuringiensis (var. kurstaki) (Btk) against the diamondback moth (DBM) on cabbage was studied at Botswana College of Agriculture, Gaborone, Botswana. Using five concentrations of Btk: 2, 4, 6, 8, and 10 g/L, bioassays were conducted against DBM eggs and second instar larvae at 30°C ± 5°C. Each treatment was replicated three times. Probit analysis was used to determine the LD₅₀ and LD₉₀ values for the treatments against eggs and larvae. When the treatments were assessed at 72, 96, 120, and 144 hours, LD₉₀ values against larvae were 11.02, 10.22, 5.92, and 4.01 g/L, whereas they were 7.71, 6.94, and 6.24 g/L against eggs when assessed 48, 72, and 96 hours after the expected time of hatching. This indicated that Btk was effective against both eggs and larvae when exposed for long periods. The slopes of the probit lines for larvae assessed at 24, 48, 72, 96, 120, and 144 hours after application were 0.250, 1.064, 0.910, 0.383, 0.453, and 0.414, while those against eggs were 1.153, 1.246, and 0.933 when assessed 48, 72, and 96 hours after the expected time of hatching. This indicates a smaller change in mortality with increase in pesticide dosage for both eggs and larvae. Btk treatments achieved 85.7%–94.6% reduction in DBM damage on cabbage. Therefore, Btk can be used to achieve effective control of DBM eggs and larvae and reduce damage on cabbage under greenhouse conditions.

Population dynamics of the Mediterranean fruit fly was studied along Montenegro seacoast. Tephri traps baited with 3 component female-biased attractants were used in 11 different localities to monitor the fruit fly population in commercial citrus orchards, mixed-fruit orchards, and in backyards. From 2008–2010, the earliest captures were recorded no earlier than July. In 2011, the first adult fly was detected in mid-June. Low captures rates were recorded in July and August (below 0.5 flies per trap per day; FTD) and peaked from mid-September to the end of October of each year. Our results indicate fluctuation of fly per trap per day depending on dates of inspection and locality, with significant differences in the adult population density. A maximum population was always reached in the area of Budva-Herceg Novi with an FTD of 66.5, 89.5, 71.63, and 24.64 (from 2008–2011 respectively). Fly activity lasts from mid-June/early-July to end December, with distinct seasonal variation in the population.

The grain-sucking bug, Stenocoris elegans Blöte (Hemiptera: Alydidae), is an important rice pest in West Africa. Investigation on its developmental biology is important to provide the base and possibility to bring forth further research for the improvement of the pest management strategy. The developmental biology of S. elegans was investigated on upland rice variety IDSA 10 in the laboratory in Ibadan, Nigeria. The results showed that pre-oviposition and post-oviposition periods were 9.9 ± 0.49 and 6.1 ± 1.17 days, respectively, under ambient temperature and relative humidity. A mated female of S. elegans laid an average of 135.1 eggs during an oviposition period of 33.5 days. The average egg incubation period was 7.9 ± 0.3 days. There were five nymphal instars, and the total developmental period (first instar to adult) averaged 18.0 days. An over-all mean growth ratio of 1.29 was recorded for this species. A regular relationship existed between measurements of nymphal vertex and the duration of their developmental periods, and a significant correlation (0.98) was obtained.

The reversible mitochondrial transhydrogenase in Manduca sexta has been characterized and is involved with endocrine-mediated post-embryonic larval development in this model insect. While biochemical in vivo and in vitro studies have been accomplished, robust molecular studies of the transhydrogenase have not been possible due to deficient genomic data. In the present study, using a combination of degenerate oligonucleotide primers and raw genomic data, we have determined the structure and sequence of the transhydrogenase gene from the model insect Manduca sexta. The encoded protein is highly similar to other transhydrogenase proteins and this sequence is the first lepidopteran sequence reported to date.

The present study presents the results of farmers’ field surveys of the sweetpotato butterfly, Acraea acerata Hew., and the two African sweetpotato weevils, Cylas puncticollis Boheman and C. brunneus F. infestation and damage. The objectives of this study were to determine (i) occurrence and distribution of A. acerata and Cylas spp. as well as infestation and losses in sweetpotato (Ipomoea batatas (L.) Lam.), and (ii) the occurrence and abundance of parasitoids of A. acerata in the Lake Albert Crescent (LAC) agro-ecological zone of Uganda. Field surveys were conducted in 240 sweetpotato fields in eight subcounties in Masindi and Buliisa districts at the end of each of the two cropping seasons of 2012 (March to May and September to November). A. acerata and Cylas spp. occurred in 17% and 90% of the fields, respectively. A. acerata did not occur in two subcounties of Buliisa district. A. acerata infestation was low, with up to two and four larvae per plant in the first and second cropping season, respectively, causing minor defoliation of up to 4.1% of the sweetpotato plant. Larvae of Cylas spp. caused root yield losses of up to 56.5% and 47.5% in the first and second cropping seasons, respectively. Parasitism rates of A. acerata larvae ranged from 0.0% to 15.1% in season 1 and 0.0% to 6.3% in season 2. Out of a total of 1020 larvae collected, 8.43% were found to be parasitized. Parasitoids occurred in 56% of fields infested by its host. Charops spp. was the main parasitoid. It was evident that Cylas spp. were more prevalent than A. acerata in the LAC agro-ecological zone of Uganda. Conservation of A. acerata natural enemies may contribute to better management of this pest. Urgent attention for management of Cylas spp. is required.

This study describes the aquatic habitats, species composition, and the insecticide resistance level of the mosquito Culex pipiens pallens in Shandong Province, China. A cross-sectional survey of mosquito larval habitats was conducted from May to November 2014 to determine the species composition and larval abundance. Larvae were collected using the standard dipping technique, and a total of four habitat types were sampled. The fourth instar larvae of Cx. pipiens pallens collected in each habitat type were tested for resistance to five insecticides according to a WHO bioassay. A total of 7,281 mosquito larvae were collected, of which 399 (5.48%) were categorized as Anopheles mosquito larvae (An. sinensis), 6636 (91.14%) as culicine larvae (Cx. pipiens pallens, Cx. tritaeniorhynchus, Cx. halifaxii, and Cx. bitaeniorhynchus), 213 (2.93%) as Armigeres larvae, and 33 (0.45%) as Aedes larvae (Aedes albopictus). In addition, a total of 1,149 mosquito pupae were collected. Culex larvae were distributed in all habitats investigated. Tukeys HSD analysis showed that roadside drainages were the most productive habitat type for Culex larvae. Armigeres species were found only in drains, Aedes only in water tanks, and Anopheles in water that was comparatively clear and rich in emergent plants. Bioassay showed that the maximum resistance level of Cx. pipiens pallens was to deltamethrin, while it was lowest to plifenate. The productivity of various mosquitoes in different habitat types is very heterogeneous. It is particularly important to modify human activity and the environment to achieve effective mosquito vector control. For effective larval control, the type of habitat should be considered, and the most productive habitat type should be given priority in mosquito abatement programs.

Bactrocera cucurbitae (Coquillett) is a tephritid fruit fly native to the Indo-Malayan region. Its distribution, though, has extended to include Africa, temperate Asia, and a number of Pacific islands. It became established in Japan in 1919 in the Yaeyama Islands and spread north in the Southwestern Islands of Japan. It was subsequently eradicated from these islands by an eradication program that extended from 1972 to 1993. As part of an effort to develop a worldwide database on the status of fruits as hosts of melon fly, the infestation data gathered from host fruits collected in this eradication program, before the initiation of suppression activities, are summarized here. Bactrocera cucurbitae infestation was documented in 24 plant taxa of four plant families (Caricaceae, Cucurbitaceae, Moraceae, and Solanaceae), with the following four new hosts identified: Ficus erecta Thunb., F. pumila L. (Moraceae), Solanum erianthum D. Don (Solanaceae), and Zehneria liukiuensis Jeffrey ex Walker (Cucurbitaceae).

Maximizing the reproductive potential of ladybird beetles fed factitious foods or artificial diets, in lieu of natural prey, is a major challenge to cost-effective mass rearing for augmentative biological control. In this study, we tested the hypothesis that compounds in redcedar, Juniperus virginiana, stimulate oviposition in the ladybird Coleomegilla maculata. We also tested the prediction that several bioflavonoids, identified in heartwood fractions, elicited this behavioral response. Phenolic compounds were extracted from J. virginiana heartwood sawdust, separated into several fractions, then presented to adult beetles, in a powdered, pure form, in the laboratory. Females preferentially oviposited within 1 to 2 cm of fractions B, C, D, and E, but not A or the unfractionated extract, at the base of test cages. Chemical analysis identified bioflavonoids in heartwood fractions and subsequent bioassays using several identified in fractions C, D, and E confirmed that quercetin, taxifolin, and naringenin (to a lesser extent) stimulated oviposition. All tested fractions and bioflavonoids readily adhered to the chorion of freshly laid eggs but did not reduce egg hatch. This study demonstrates that several bioflavonoids stimulate oviposition by C. maculata and could be useful for mass rearing programs.

Recently, Taylor-Wells et al published evidence that the γ-aminobutyric acid (GABA) receptor, resistance to dieldrin (RDL), from mosquitoes undergoes RNA A-to-I editing to generate an extraordinarily large range of isoforms. This editing was found to affect GABA receptor pharmacology, as it influenced the potency of GABA and ivermectin. This highlights RNA editing as a species-specific mechanism to fine-tune receptor function as well as possibly increase tolerance of mosquitoes to certain insecticides. This commentary also considers novel findings from analysis of Rdl transcripts from individual mosquitoes taken from different geographical areas.

Flavonoids are important plant secondary metabolites, which protect plants from various stresses, including herbivory. Plants differentially respond to insects with different modes of action. High performance liquid chromatography (HPLC) fingerprinting of phenols of groundnut (Arachis hypogaea) plants with differential levels of resistance was carried out in response to Helicoverpa armigera (chewing insect) and Aphis craccivora (sucking pest) infestation. The genotypes used were ICGV 86699, ICGV 86031, ICG 2271 (NCAc 343), ICG 1697 (NCAc 17090), and JL 24. Most of the identified compounds were present in H. armigera- and A. craccivora-infested plants of ICGV 86699. Syringic acid was observed in all the genotypes across the treatments, except in the uninfested control plants of ICG 2271 and aphid-infested plants of ICG 1697. Caffeic acid and umbelliferone were observed only in the H. armigera-infested plants of ICGV 86699. Similarly, dihydroxybenzoic acid and vanillic acid were observed in H. armigera- and aphid-infested plants of ICG 2271 and JL 24, respectively. The peak areas were transformed into the amounts of compounds by using internal standard peak areas and were expressed in nanograms. Quantities of the identified compounds varied across genotypes and treatments. The common compounds observed were chlorogenic, syringic, quercetin, and ferulic acids. These results suggest that depending on the mode of feeding, flavonoids are induced differentially in groundnut plants.

The stem borer Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is an important pest of maize and sorghum in sub-Saharan Africa. This insect has oligophagous feeding habits, feeding mostly on maize and sorghum with a narrow range of wild Poaceous plant species. We hypothesised that first instar B. fusca larvae, the critical stage for successful establishment on a host plant, can establish and then grow on a particular plant as a result of induction of a complement of digestive enzymes that mediates host acceptance at first instars. A fast semi-quantitative analysis of potentially digestive enzymatic activities present in the first larvae previously fed for 4 days on leaves of host and non-host plants was performed using the API-ZYM kit system able to detect a multiplex of enzyme activities. Regardless of the plant species, the larvae exhibited higher activities of the carbohydrate metabolising enzymes than of aminopeptidases and proteases. In addition, highest activities of carbohydrates degrading enzymes were exhibited by larvae that consumed leaves of the most preferred plant species of B. fusca. Conversely, esterases were only detected in neonate larvae that consumed leaves of the less preferred and non-host plants. No alkaline phosphatase and lipase activities were detected. The significance of these results was discussed in terms of food requirements of first instar larvae when settling on a plant.

The cashew stem girdler, Analeptes trifasciata, is a major insect pest of cashew in Nigeria causing economic damage in cashew plantations even at low density. In this study, newly emerged adults of A. trifasciata reared from field-infested cashew stems were collected from the rearing cages, sexed, and dissected to reveal the internal structures of the insects. The gut was excised and separated into the foregut, midgut, and hindgut. The dissected gut compartments were blotted dry by sandwiching in sterile Whatman No. 1 (150 mm) filter paper for a minute. The inoculated gut parts showed the presence of eight fungi flora, namely, Aspergillus repens, Trichoderma spp., Fusarium verticillioides, Lasiodiplodia theobromae, yeast, Aspergillus niger, Fusarium spp., and Rhizopus stolonifer. The frequencies of occurrence of bacteria in the gut compartments of A. trifasciata were Enterobacter spp.: 83.33%; Escherichia coli and Streptococcus spp.: 55.56% each; Staphylococcus spp.: 44.44%; Klebsiella pneumonia: 50% and Salmonella shigella: 11.11%, while each of Serratia marceascea, Pseudomonas spp., and Micrococcus lutea had 5.56% occurrence. The occurrence of mycoflora and microbiota species varied in the gut compartments of A. trifasciata, indicating the role of these microorganisms in metabolic and other bioprocesses of A. trifasciata during digestion and synthesis of complex food substances from the cashew stem substrate. This study would provide basic information for enzymatic studies of A. trifasciata with a view to developing an integrated pest management (IPM) protocol for managing the pest in cashew plantations.

AIMS AND SCOPE: The aim of this special collection is to highlight the importance of reproduction (ie, oviposition) in the life history, population dynamics, survival, and fitness of beneficial insects, broadly defined. Specific areas of interest include the (1) identification of natural products to boost oviposition; (2) importance of chemical cues in oviposition site selection; (3) influence of host plant defenses on oviposition success; (4) reproductive physiology and the frequency of egg laying; (5) trade-offs between maternal size and egg size; (6) foraging behavior, host selection, and oviposition in parasitoids; and (7) oviposition decisions in the face of intraguild predators.

Plants produce proteins such as protease inhibitors and lectins as defenses against herbivorous insects and pathogens. However, no systematic studies have explored the structural responses in the midguts of insects when challenged with plant defensive proteins and lectins across different species. In this study, we fed two kinds of protease inhibitors and lectins to the fruit fly Drosophila melanogaster and alpha-amylase inhibitors and lectins to the cowpea bruchid Callosobruchus maculatus. We assessed the changes in midgut cell structures by comparing them with such structures in insects receiving normal diets or subjected to food deprivation. Using light and transmission electron microscopy in both species, we observed structural changes in the midgut peritrophic matrix as well as shortened microvilli on the surfaces of midgut epithelial cells in D. melanogaster. Dietary inhibitors and lectins caused similar lesions in the epithelial cells but not much change in the peritrophic matrix in both species. We also noted structural damages in the Drosophila midgut after six hours of starvation and changes were still present after 12 hours. Our study provided the first evidence of key structural changes of midguts using a comparative approach between a dipteran and a coleopteran. Our particular observation and discussion on plant–insect interaction and dietary stress are relevant for future mode of action studies of plant defensive protein in insect physiology.

Literature is reviewed on the spatial distribution of the eggs and neonate larvae of codling moth on apple trees in relation to research conducted in Nelson, New Zealand. At Nelson, oviposition increased with height and was greater in the north and east of the trees and in those with greater fruit load in some seasons, which matches published reports. All publications and the research recorded high percentages of eggs laid singly within 10–15 cm of the fruit, with most eggs on leaves even within fruit clusters; oviposition on fruit clusters of different sizes was nonrandom because more eggs were laid on those with more fruit, but the aggregation of both per cluster and within clusters was even greater than that caused by the fruit number alone. Oviposition at random with respect to the fruit occurred only at very low population density. The choice of oviposition site between fruit and the adaxial leaf surface and abaxial leaf surface (AbLS) was variable and cultivar related. Cultivars on which eggs predominated on the AbLS were less frequent and characterized by low trichome density. In the literature, neonate larvae from eggs on the AbLS suffered greater mortality, as did those in Nelson that hatched more distant from the fruit. This review discusses the interaction between these distribution characteristics and species-specific host–plant volatiles, egg adhesion to plant surfaces, oviposition deterrents, predation, and their relevance to pest management.