Mass-rearing of the redlegged ham beetle, Necrobia rufipes De Geer (Coleoptera: Cleridae) for laboratory research

A new protocol for mass-rearing the redlegged ham beetle, Necrobia rufipes De Geer, in the laboratory is described, that facilitates the production of large numbers of insects with minimal handling. A culture medium comprised of finely ground (150 μm) dried fish, dry dog food and pieces of dried cured ham was tested on N. rufipes. This rearing medium produced significantly larger population numbers when compared with a range of published and unpublished methods. When reared on this medium with initial colonies of 200 mixed sex adult beetles, there was more than a three-fold increase in N. rufipes adult populations from the original numbers over a 7-8 week period. This simple procedure minimizes cannibalism as the larvae were shifted into glass vials for pupal cell formation.     

Sulfuryl fluoride as a methyl bromide alternative for fumigation of Necrobia rufipes (Coleoptera: Cleridae) and Tyrophagus putrescentiae (Sarcoptiformes: Acaridae), major pests of animal-based stored products

Sulfuryl fluoride (SF) has been registered in many countries for stored product applications as an alternative to other fumigants, especially methyl bromide (MB). Research was conducted to establish SF fumigation protocols for the mortality of pests infesting post-harvest durable commodities. The efficacy of SF against two major arthropod pests of southern dry-cured hams, the red-legged ham beetle, Necrobia rufipes, and the ham mite, Tyrophagus putrescentiae, was investigated. SF caused significant mortality in ham beetles but not for ham mites when treated for 48 h at 23 °C. Eggs of N. rufipes were more tolerant to SF than other stages fumigated. In addition, early aged (1–2 d old) eggs of N. rufipes were more susceptible to SF than late-aged (4–5 d old) eggs. Furthermore, SF fumigation led to 100% control of larvae, pupae and adults of N. rufipes by 8 g/m³ while the eggs required 20.88–24.72 g/m³ to prevent 100% hatch. However, T. putrescentiae showed high tolerance to SF as it survived concentration-time products in excess of the standard label limit 1500 g h/m³. SF studies also revealed that the eggs of T. putrescentiae were several fold more tolerant than that of the mobile stage, the nymphs and adults. SF trials under pilot-scale commercial conditions were also carried out that further supported the efficacy of SF for red-legged ham beetles but not for the ham mite. SF may not be suitable for managing ham mites based on work to date, but future work could investigate longer exposure times at higher temperatures.     

Population growth of the khapra beetle,Trogoderma granarium Everts (Coleoptera: Dermestidae) on different commodities

We evaluated the population growth of the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae) on different grains, cracked wheat containment categories and amylaceous materials by conducting three series of laboratory bioassays. In the first series, peeled barley, whole (raw) barley, peeled oats, whole (raw) oats, peeled rice, rough rice, rye, triticale and hard wheat were tested. In the second series, six cracked wheat containment categories were tested: wheat containing intact kernels only (0% cracked kernels), wheat containing 5% cracked kernels and 95% intact kernels, wheat containing 10% cracked kernels and 90% intact kernels, wheat containing 25% cracked kernels and 75% intact kernels, wheat containing 50% cracked kernels and 50% intact kernels and wheat containing 100% cracked kernels. In the third series, the following amylaceous commodities were tested: hard wheat (intact kernels), whole oat flakes, maize flour, whole barley flour, pasta, white soft wheat flour, whole soft wheat flour, white hard wheat flour, whole hard wheat flour, whole rye flour and semolina. Significantly more dead adults were found on wheat than on peeled barley, maize, whole oats, rough rice and rye. Significantly more larvae alive were found on wheat and triticale, than on the other grains, with the exception of oats, both whole and peeled. The increase of the percentage of cracked wheat kernels increased population growth, except in the case of 10% cracked wheat kernels. In vials that contained 100% cracked wheat kernels, 584.1 individuals per vial were found, which was 3.7 times more than the respective number of larvae alive in vials with intact wheat kernels only. Significantly more dead adults were found on whole barley flour than on the other commodities. More than 1213 larvae per vial were recorded on whole barley flour, which was 1.3–15 times higher than the other commodities. The lowest number of larvae alive was found on pasta, followed by the white soft wheat flour. The findings of the present work show that some commodities are more prone to spread T. granarium than others, a fact which should be seriously taken into account in international trade of grains and related amylaceous products.     

Biology and management of Plodia interpunctella (Lepidoptera: Pyralidae) in stored products

Plodia interpunctella (Hübner), the Indian meal moth, is a world-wide insect pest of stored-products and processed food commodities. It can infest a variety of products and is perhaps the most economically important insect pest of processed food. In this review, we summarize the biology of P. interpunctella, discuss oviposition and development in relation to temperature, environment and food source, examine studies involving sampling and detection, describe various aspects of integrated control, summarize the current knowledge regarding management of P. interpunctella, and address potential areas for new research. The use of reduced-risk insecticides, non-chemical control, targeted pest management through spatial analysis and other means of identifying specific locations of infestations, and computer models that simulate population growth, are examples of some of those new areas of research.     

Different diets affecting biology and digestive physiology of the Khapra beetle,Trogoderma granarium Everts (Coleoptera: Dermestidae)

The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is a serious pest of grain and other stored products through the world. In this research, effect of five host diets including barley, rice, rye, wheat and walnut was studied on some of biological traits, nutritional indices and digestive enzymatic activity of T. granarium at 33 ± 1 °C, 65 ± 5% RH and a photoperiod of 14:10 (L:D) h. The Khapra beetle larvae reared on walnut had the highest number of larval instar and longest duration of larval and pupal stages (91.30 ± 0.4 days). The heaviest pupal weight of T. granarium was on rye (4.22 ± 0.01 mg) and the lightest weight was on rice (3.99 ± 0.01 mg) and walnut (4.00 ± 0.01 mg). The highest realized fecundity and fertility were recorded for the females reared on rye (45.88 ± 1.08 eggs/female and 69.39 ± 0.68%, respectively) and wheat (49.02 ± 1.55 eggs/female and 67.54 ± 0.69%, respectively), and the lowest ones were observed for the females came from larvae fed walnut (15.45 ± 0.71 eggs/female and 34.55 ± 0.82%, respectively). Also, the results showed that T. granarium larvae reared on walnut had the lowest values of the efficiency of conversion of ingested food (7.67 ± 0.04%) and relative growth rate (0.044 ± 0.0002 mg/mg/day). The lowest midgut amylolytic (0.044 ± 0.0005 and 0.047 ± 0.0005 mU/individual, respectively) and proteolytic (0.015 ± 0.0004 and 0.016 ± 0.0001 mU/individual, respectively) activity of the sixth instar was detected on walnut and rice. The highest inhibition of amylase (53.37 ± 0.75%) and protease activity (48.54 ± 0.96%) was estimated by incubating midgut extracts from the last instars with wheat and barley proteinaceous extracts, respectively. The results indicated that walnut was the most unsuitable diet for feeding and development of T. granarium.     

Biology, behaviour and environmentally sustainable control of Tineola bisselliella (Hummel) (Lepidoptera: Tineidae)

This review summarises the information available on the biology, behaviour and economic significance of the common or webbing clothes moth, Tineola bisselliella (Hummel), currently the most important and widespread clothes moth pest throughout the world. These moths can cause the loss of irreplacable material of aesthetic, historic and scientific importance, as well as damaging every-day items such as clothes, furnishings and other materials prepared from animal fur, wool, feathers and hides. Methods for the detection and control of this pest are outlined, with particular emphasis on control strategies that are environmentally sustainable and avoid the use of conventional pesticides and fumigants. Improvements in storage coupled with targeted use of appropriate control measures will help to reduce pest populations. However, the continuing problems with this pest highlight the need for improved methods of detection, prevention and management.     

Influence of commodity on the population growth of the larger grain borer,Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae)

In this study, we compared different amylaceous commodities for their suitability for population growth of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae), which is an important pest of stored maize in the tropics. In this context, we conducted three different series of tests. In the first test, we compared whole grains: whole barley, peeled barley, maize, whole oats, peeled oats, peeled rice, rough rice, rye, triticale, and wheat. Only maize was found suitable for P. trunctatus to reproduce and significantly increase its population, but there were certain commodities where surviving adults were found. In the second series of tests, we evaluated the percentage of cracked maize kernels on P. truncatus population growth. In this test, we found that the numbers of alive P. truncatus adults in the vials that contained 100% cracked kernels was higher than these with lower percentages of cracked kernels (5–50%) or no cracked kernels (0%). Finally, in the third series of tests, we compared eleven different types of amylaceous commodities with maize. These commodities were: whole maize (whole kernels), whole oat flakes, maize flour, whole barley flour, pasta, white soft wheat flour, whole soft wheat flour, white hard wheat flour, whole hard wheat flour, whole rye flour, and semolina. The results indicated that only whole maize and maize flour were suitable for P. truncatus population growth. Nevertheless, in some of the other commodities tested, there was a low number of adults and immatures that were able to survive 60 days after the incorporation of the parental adults. The results of the present study indicate that from the commodity range tested here, only maize was suitable for P. truncatus population growth. Nevertheless, the marginal numbers of surviving individuals in the non-maize commodities and the role of these substrates as potential “non-preferred food vehicles” that may contribute to further spread of this species should be tested in more detail.     

Life history of Trogoderma granarium Everts (Coleoptera: Dermestidae) on peeled barley,peeled oats and triticale

The life history of the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), was investigated on cracked peeled barley, cracked peeled oats and cracked triticale. The results suggest that the biological and demographic parameters of T. granarium are affected by the tested commodities. The developmental time of total immature period of T. granarium was significantly lower on barley (35.06 days) than on oats (42.87 days) and triticale (43.58 days). Mean longevities of adult females were 7.00, 7.89 and 8.24 days, and for adult males were 5.79, 6.05 and 5.49 days when T. granarium fed on barley, oats and triticale, respectively. The highest fecundity recorded when T. granarium fed on barley (39.0 eggs/female) or triticale (35.2 eggs/female), but it was significantly lower when this species fed on oats (25.4 eggs/female). While the net reproductive rate did not differ significantly when T. granarium fed on barley (14.6 females/female), oats 10.2 (females/female) and triticale (11.0 females/female), the mean generation time was significantly lower when fed on barley (40.5 days) than on oats (48.7 days) and triticale (46.1 days). The intrinsic rate of increase of T. granarium did not differ significantly when fed on barley and triticale (0.066 and 0.052 females/female/day, respectively), but it was significantly lower when fed on oats (0.047 females/female/day). The biological and demographic parameters of T. granarium may be incorporated in population models that evaluate the population dynamics aiming to the optimization of management strategies against this noxious species.     

Feeding substrate and temperature interplay determining infestations and losses by the sawtoothed grain beetle (Oryzaephilus surinamensis)

Sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), is a secondary pest of stored products and one of the serious insect pests of cereal grains, commodities and packaged food throughout the world. However, this species is a concern beyond cereal grains, what may be differentially affected by temperature. Therefore, insect developmental time, larva and pupa survival, and adult emergence of O. surinamensis were assessed on different substrates (rice, sesame and date palm) at different temperatures (20, 25, 30 and 35 °C and 65% r.h). The substrate loss incurred by this insect infestation was also recorded. The larval stage was the main determinant for the overall developmental time of the sawtoothed grain beetle, regardless of the substrate and temperature tested. Adult emergence was affected by substrate (F_2,48 = 4.50, P = 0.02) and particularly temperature (F_3,48 = 24.94, P < 0.001), but not their interaction (F_6,48 = 0.40, P = 0.87), exhibiting little variation until reaching 30 °C, but with a quick decline at 35 °C. The performance of the insects in rice was better, and worse in dry date. Furthermore, the survival was inversely related to substrate loss, regardless of the substrate used for rearing the sawtoothed grain beetle. Thus, substrate and temperature range are major determinants of sawtoothed grain beetle infestation with consequences for this species management.     

Maize hybrids affected nutritional physiology of the khapra beetle,Trogoderma granarium Everts (Coleoptera: Dermestidae)

The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is an important insect pest of stored cereals, grains and other stored products in Iran and some countries of the world. Nutritional indices and digestive enzymatic activity of fifth instar T. granarium were investigated on nine maize hybrids (704, AR 89, AS 71, AS 77, BC 678, KSC 703, PL 472, SC 704, and Simax) at 33 ± 1 °C, relative humidity of 65 ± 5%, and a photoperiod of 14: 10 (L: D) h. The highest and lowest food consumption by larvae was on AR 89 and BC 678, respectively. Fifth instar larvae fed on 704 had the highest efficiency of conversion of ingested food, and those fed on BC 678 showed the lowest relative growth rate. The larval growth index, standardized insect-growth index and fitness index were the highest when larvae were reared on PL 472, and the lowest when they were reared on BC 678. The highest proteolytic and amylolytic activity was on KSC 703, and the lowest activity was on BC 678. The results of this study indicated that BC 678 was an unsuitable hybrid for feeding of fifth instar T. granarium. Studying the nutritional physiology of T. granarium on different maize hybrids can be useful in identifying the anti digestive compounds of host grains, which can be expressed in genetically engineered crops to confer resistance to this key pest.     

Oviposition of Dermestes maculatus DeGeer,the hide beetle,as affected by biological and environmental conditions

Experiments were conducted to document the oviposition behaviors and preferences of the female hide beetle, Dermestes maculatus DeGeer, in order to optimize the collection of eggs and neonate larvae for biological assays. Factors evaluated were the type of oviposition substrate, preference for and type of preconditioned diet, sex ratio and light/dark conditions. We determined that synthetic fur was a suitable medium for oviposition and collecting progeny. Fur type and position were not important factors in oviposition preference (average progeny production ranged from 27.9 ± 6.4 to 42.4 ± 6.4); however, the use of paper as a cover and no cover treatments were statistically different from the fur treatments and resulted in average progeny productions of 5.2 ± 1.1 and 3.4 ± 0.7, respectively. Diet preconditioned by the colony was a statistically significant (P < 0.001) factor for oviposition preference, compared with unconditioned diet, and inhibited oviposition. The type of preconditioning was also an important factor (P = 0.004); we examined four treatments: no conditioning, conditioning by larvae, conditioning by adult males and conditioning by adult females. The mean progeny production for the control (no conditioning) was 52.9 ± 13.6, which was not significantly different from the larval conditioning treatment (48.1 ± 5.9). Both adult conditioned treatments were statistically different for progeny production, adult male (22.3 ± 2.9) and adult female (8.2 ± 2.5). In regard to sex ratio affecting progeny production, oviposition was greatest with only one male. Mixed results were obtained in light verses dark conditions and further experiments regarding the effects of day length on oviposition would be useful for optimizing oviposition of D. maculatus.     

Asymmetric courtship boosts male mating success in the red flour beetle,Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Recently, the functional asymmetries of courtship and mating behavior in several major pests of economic importance at the post-harvest stages of agricultural commodities have been reported. In this study, we investigated the presence of population-level behavioral asymmetries in the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) mating pairs. Males showed left-biased population-level courtship attempts when approaching potential mates. Furthermore, no significant differences were recorded for the duration of mate recognition and copula of males approaching females from the left, right side or backside. However, precopula and whole mating duration differ significantly among males approaching females from the left, right or backside. On the other hand, lateralization of courtship attempts had a significant impact on male mating success. Left-biased courtship attempts of T. castaneum males led to a higher male mating success, as compared to right-biased and backside courtship attempts. To the best of our knowledge, this is the first study investigating the impact of side-biased courtship attempts on male mating success in T. castaneum. Moreover, our findings add basic knowledge to the mating and reproductive behavior of this important pest that damages foodstuffs worldwide, which can be useful to optimize rearing procedures of this beetle, minimizing mating success reductions due to prolonged mass-rearing. Furthermore, knowledge about the mating behavior of T. castaneum can be utilized further towards the development of traps and attractants for this pest.     

Comparative performance of the Khapra beetle,Trogoderma granarium Everts (Coleoptera: Dermestidae) on various wheat cultivars

The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is known as a serious pest of stored grains and stored products. Host plant is an effective ecological factor on performance of an insect pest. In this study, effects of ten wheat cultivars were evaluated on life table parameters and nutritional indices of T. granarium under laboratory conditions, 33 ± 1 °C, 60 ± 5% RH and a photoperiod of 14: 10 (L: D) h. Our research showed that various wheat cultivars have significant effects on life history, demographical parameters and nutritional indices of T. granarium. The highest immature survival rate was observed on cultivar Gaskojen. Significant differences on developmental time, adult fecundity and longevity of T. granarium were found across tested wheat cultivars. In addition, there were significant differences among the wheat cultivars for population growth parameters of T. granarium. The highest (r_m) values were observed on Gaskojen (0.078 eggs/female/day) and its lower values were resulted from rearing of T. granarium on Kouhdasht and Bezostaya. The larvae fed on Gaskojen showed the higher value of food consumption as compared with others. In addition, the higher value of relative growth rate (RGR) was found on cultivar Gaskojen, while the relative lower value was observed on cultivar Kouhdasht. The results indicated that Gaskojen cultivar was a relatively susceptible wheat cultivar and Kouhdasht cultivar was relatively unsuitable host for feeding of T. granarium which could prove useful in the development of IPM programs for this pest.     

Screening of chickpea accessions for resistance against the pulse beetle,Callosobruchus chinensis L. (Coleoptera: Bruchidae)

During storage, chickpea (Cicer arietinum L.) is severely attacked by some bruchid species, especially Callosobruchus chinensis L. (Coleoptera: Bruchidae), resulting in losses in quantity and nutritional quality. In the present study, three species of Cicer including five accessions of Cicer arietinum L. (three kabuli and two desi chickpeas), four accessions of C. echinospermum P.H. Davis and five accessions of C. reticulatum Ladiz. were screened for resistance to C. chinensis in both free-choice and no-choice tests in the laboratory. Resistance was evaluated by measuring oviposition (number of eggs per seed), adult emergence (number of holes per seed), damaged seed rate and seed weight loss (%). The results revealed that no eggs were laid by the bruchid females to the C. echinospermum accessions in free-choice test, but in no-choice test only two C. echinospermum accessions (AWC 304 and AWC 305) had few eggs (4.3 and 3.3 eggs/seed, respectively). The highest rate of oviposition occurred in kabuli chickpeas, especially in YAR (25.1 eggs/seed in free-choice test). The accessions exhibited a similar pattern for adult emergence like in the oviposition rates. As for damaged seed rate, no damage was observed in both tests in the C. echinospermum accessions, except AWC 304 (6.7%) in no-choice test. The highest seed damage was seen in kabuli-type accessions, being 100% in YAR and ILC 8617. Considering seed weight loss, no weight loss occurred in the C. echinospermum accessions in both tests (except, AWC 304 in no-choice test) whereas the highest weight loss was seen in the kabuli-type accession, CA 2969 (28.6%) in free-choice test and in the desi type accession, ICC 4957 (35.0%) in no-choice test. Since lower numbers of eggs were laid on hairy, wrinkled/reticulated and dark seed accessions, these features seemed to be important in the preference of the bruchid for host selection and oviposition. These results suggest that resistant varieties can be used as gene sources in breeding new cultivars resistant to C. chinensis.     

The biology,ecology and management of the larger grain borer,Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)

The invasive larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), originating from Meso-America, is a devastating stored product pest of maize (Zea mays L.) and cassava (Manihot esculenta). This species can destroy up to 40% of stored maize within four months. Despite four decades of research, P. truncatus has spread throughout Africa, while decimating maize and cassava production. Given the continuing problems with P. truncatus, the likelihood for its continued range expansion under climate change, and its status as a species of concern in many countries, the objective of this review was to provide an updated and comprehensive freely accessible record of the distribution and spread, biology, development, and ecology, host preferences, chemical ecology, detection, and monitoring, and management of P. truncatus. We conducted a search of the literature from 1911 to 2021 using Google Scholar and Web of Science to find all papers related to key search terms. We found that P. truncatus has been recorded in 36 countries across the globe, including 21 now in Africa. A recent predictive model found that the insect has been limited to tropical and subtropical regions but could likely spread to temperate regions as temperatures rise with climate change. Conspecifics respond to their two component, male-produced aggregation pheromone early after eclosion, but quickly switch to other cues as older adults. At close-range, P. truncatus may use food cues, but host volatiles are not involved in long-range host finding of commodities. Research on managing P. truncatus has mostly focused on chemical control to the detriment of other tactics, with the most promising tactic likely to be the different hermetic storage technologies. Many outstanding areas of basic behavior and ecology remain to be assessed for P. truncatus. We highlight specific areas that should be prioritized for further work in order to better manage and reduce the impact of this invasive insect pest.     

Repellency and toxicity of troponoid compounds against the adzuki bean beetle, Callosobruchus chinensis (L.) (Coleoptera: Bruchidae)

We compared the repellency and toxicity against adzuki bean beetles among six troponoid compounds, and examined the relationship between their structure and activity. γ-Thujaplicin showed the highest repellency against the beetles among the compounds tested, while the repellency of tropiliden was quite low. The results suggested that the keto and hydroxyl groups are important in the repellent properties of troponoid compounds. Although an isopropyl group was also important in repellency, the effect varied according to its position on the seven-member ring; the farther the isopropyl group was from the keto and hydroxyl groups, the higher the repellency became. As with its repellency effect, the toxicity of tropiliden was quite low. Tropone showed the highest toxicity among the compounds tested while its repellency was relatively low. Similar to its repellency, γ-thujaplicin showed the highest toxicity among the thujaplicins. However, the toxicities of α-thujaplicin and β-thujaplicin (hinokitiol) were similar, unlike the repellency. In summary, it appears that the toxicity of troponoid compounds does not always coincide with their repellency. Furthermore, the repellency and toxicity of a mixture of γ-thujaplicin and β-thujaplicin, whose production cost is cheaper than that of hinokitiol alone, were investigated. The mixture strongly repelled the adzuki bean beetles. We conclude that the mixture of γ-thujaplicin and β-thujaplicin is a promising repellent.     

Identification and characterization of surface lipid components of the dried-bean beetle Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae)

The dried-bean beetle Acanthoscelides obtectus is a major post-harvest pest, which can cause up to 30% losses from dry-stored beans. For the use of microbial agents for biocontrol of A. obtectus, it is of importance to identify cuticular lipids of this pest, if we are to understand the factors responsible for preferential adhesion or selective repulsion of entomopathogenic fungi that are potentially useful for biocontrol.The cuticular lipids of adult A. obtectus of both sexes were found to consist of hydrocarbons, aldehydes, methyl- and ethyl-esters of fatty acids, triacylglycerols, free fatty acids, alcohols and sterols. All the fatty acids identified in this study were found in both ether extracts and dichloromethane extracts. The dominant fraction of all the lipids isolated from this species consisted of C_16:0, C_18:0, C_18:1, C_18:2 and C_18:3 compounds. Males and females contained similar amounts of hexadecanoic acid, but there was a significant difference between the total amounts of C_18:0, C_18:1 and C_18:2 acids in the two groups. We have also successfully identified one of the sesquiterpenes present in the cuticle as α-farnesene.     

Aerosol concentration,deposition, particle size,and exposure interval as mortality factors Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

A series of trials was conducted for an experiment. In the first trial, adults of Tribolium confusum Jacquelin du Val, the confused flour beetle, were exposed on concrete arenas and treated with a combination aerosol of pyrethrin + methoprene dispensed for 5, 10, and 20 min at particle sizes of 4, 8, 12, and 16 μm, inside an aerosol exposure chamber. Nearly all adult T. confusum were knocked down when immediately removed from the chamber. Among all the exposure time and particle size combinations, recovery increased as the post-exposure holding period increased from one to seven days and when adults were transferred to untreated dishes with flour. A second experiment evaluated the residual effect of the aerosol on concrete arenas at 1, 3, and 6 weeks using 3-4-week-old larvae of T. confusum. Adult emergence of exposed larvae decreased with increasing particle size and exposure time. A biological index that assessed development of exposed larvae to the pupal and adult stages was also related to particle size and exposure interval, and this index was correlated with adult emergence. A third set of experiments investigated effects of particle size on adult fecundity for the 10-min exposure time. Male and female adults were cross-mated: exposed female with exposed male, exposed female with unexposed male, exposed male with unexposed female, and unexposed female and unexposed male. Progeny production was reduced as particle size increased, and there were indications that females were affected more than males by the aerosol treatment. This research could be used to improve insect pest management programs by adjusting application equipment to dispense aerosols at particle sizes that give optimum control of exposed adults and residual control of immatures and would also benefit pest management programs.     

Clarification of the role of 4-methylnonanol,female-produced sex pheromone of the yellow mealworm beetle,Tenebrio molitor (Coleoptera: Tenebrionidae)

The objective of this study was to clarify the role of (4R)-(+)-4-methyl-1-nonanol (MNol), a female-produced sex pheromone, in mediating the mating behavior of male Tenebrio molitor L. beetles. The abilities of MNol and authentic female extract (FE) to attract virgin males and to elicit copulatory behavior (CB) from the males were determined by bioassay. Hollow glass rods were used to mimic females. The samples of interest were assayed by coating each either on the outside or on the inside surface of the hollow rods, in order to determine if the responses were due to volatile pheromones (which would be perceived whether coated on the inside or the outside of the rods) or to “contact” pheromones (which would be perceived only when coated on the outside of the rods). The responses of virgin male beetles (6–11 days post-emergence) to FE, MNol, or pentane (control) were compared at both high and low concentrations (n = 10 for each treatment). MNol and the FE showed a similar ability to attract males, at either high or low concentrations. At high concentrations, both MNol and the FE elicited CB from the males. However, unlike the FE, at low concentrations MNol was unable to elicit CB from the males. Thus the FE must contain at least one separate “copulation pheromone” that can elicit the CB at low concentrations. Furthermore, the observed “copulation pheromone” must be volatile, since no difference in response was observed whether the FE was coated on the inside or on the outside surface of the hollow rods. Thus the biological role of MNol is likely to attract males to the females and, once the male is in the immediate vicinity of the female, to act in concert with other pheromones (of which at least one is volatile) to facilitate copulation.     

Biology,morphology and molecular characterization of Sitophilus oryzae and S. zeamais (Coleoptera: Curculionidae)

The present study focuses on the variations in biology, morphology and mitochondrial cytochrome oxidase I (mtCOI) sequences of the two Indian populations of the rice weevil Sitophilus oryzae (L.) and S. zeamais (Motschulsky) (Coleoptera: Curculionidae), which occur on cereals as storage grain pests. These two species are the important pest of major importance and morphologically are very similar to each other. The biological study reveals that the developmental period, longevity, mating and premating period are longer in S. zeamais compared to S. oryzae. The developmental periods of eggs, first to fourth instar larvae, pupae and adults were 6.9, 5.8, 7.0, 8.4, 7.5, 12.5 and 3.5 days, respectively with total life cycle duration of 51.6 days in S. zeamais; and it was 5.5, 5.0, 5.7, 6.5, 7.0, 7.4 and 2.4 days, respectively with total life cycle duration of 39.1 days in S. oryzae. Morphometrics of the life stages revealed significant differences in the dimensions of length and width except in case of eggs and fourth instar larvae. Since, morphological identification were quite confusing and difficult, some characters such as dentations on fore tibia, gular suture on rostrum, apex of 8th tergite and variation in the spermatheca, are brought out as additional diagnostic characters. This study evaluated the utility of mtCOI sequences for quick and accurate species diagnosis of S. oryzae and S. zeamais independent of life stages and sex. The phylogenetic analyses revealed that among the four species of the genus Sitophilus, S. oryzae and S. zeamais cluster together (1.0 PP and 84% ML) and are closer to S. linearis (Hbst.) than S. granarius (L.).