Post-copulatory Mounting Behavior of the West Indian Sweetpotato Weevil, Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae)

Post‐copulatory associations between males and females have been found in a variety of insects and are often described as mate guarding. Males of the West Indian sweetpotato weevil Euscepes postfasciatus (Fairmaire) mount the female's back after copulation. Two hypotheses have been advanced to explain this behavior: mate guarding to prevent future copulations by rivals (hypothesis 1), and mate guarding to gain additional copulations (hypothesis 2). We conducted three experiments to test predictions from these hypotheses. Our results disproved hypothesis 1 because the duration of the post‐copulatory association was very brief in comparison with the length of the refractory phase all females showed after copulation. When we prevented females from resisting copulations during the post‐copulatory mounted phase males copulated again, while under normal conditions, a second copulation was never observed. This result may indicate the presence of a sexual conflict over mating. However, we propose an alternative interpretation of the result, namely that after mating, males test whether the copulation has successfully reduced female receptivity by attempting to remate. If females resist the mating, males leave.     

Trail Marking and Processionary Behavior of the Larvae of the Weevil Phelypera distigma (Coleoptera: Curculionidae)

We present here the results of an investigation of the behavioral bases of the first documented instance of trail marking and processionary behavior in a beetle. The larvae of Phelypera distigma (Coleoptera: Curculionidae) forage communally, moving over the host plant in head-to-tail processions. Our study shows that the larvae secrete a pheromone from the ventral surface of the posterior abdomen that both elicits and guides the collective locomotion of the cohort. The pheromone is soluble in acetone and other nonpolar solvents and is relatively short-lived, eliciting trail following for less than 4 h after its deposition. When in processionary formations, larvae stimulate locomotion in others by rapidly bobbing their heads against sets of setae that occur on the lateral flanks of the posterior tips of the abdomens of precedent individuals. Larvae are also strongly attracted to tactile or chemotactile stimuli found at the tip of the abdomen of other larvae and their response to lures made of eviscerated abdomens show that such stimuli take precedence over the trail pheromone in eliciting and orienting locomotion. The cycloalexic formations adopted by resting larvae maximize the amount of body contact possible in a two-dimensional aggregate and allow tactile signals to rapidly radiate through the groups, alerting all members of a cohort to the onset of bouts of activity.     

Mating Behavior of the Coffee Berry Borer, Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae)

The mating behavior of the coffee berry borer, Hypothenemus hampei (Ferrari), was observed under laboratory conditions. Pairs of adult virgin male and female beetles were placed in the wells of a polystyrene microtiter plate, one pair per well. The mating activity of each pair was recorded for 24?h. The mating behavior of the coffee berry borer was similar to that of other Scolytinae and was clearly divided into precopulatory, copulatory and postcopulatory phases. The beetles started to mate within a few hours of emergence. Repeated mating occurred during the 24-hour period and increased in frequency with age. However, we cannot address multiple matings in H. hampei, since we did not simulate the female-biased sex ratio of this species and the experimental design did not allow females to avoid additional mating attempts by males. In addition, further studies are necessary that focus on the effectiveness of sperm transmission and direct and indirect effects of multiple matings on the H. hampei females and their offspring.     

Social Behavior of Larvae of the Neotropical Processionary Weevil Phelypera distigma (Boheman) (Coleoptera: Curculionidae: Hyperinae)

Socially gregarious behavior among free‐living leaf‐eating insect larvae occurs mostly among Lepidoptera, Symphyta, and a few Chyrsomelidae (Coleoptera). However, the Neotropical hyperine curculionid Phelypera distigma has also evolved this lifestyle, exhibiting a suite of social behaviors unique among beetles. The larvae are nomadic processionary foragers that punctuate foraging bouts with rosette‐shaped resting formations (cycloalexy). Larvae also vibrate or bob their heads rapidly when moving, especially when in contact with conspecifics, and this suggests acoustic or vibrational communication. In this study we used observational and experimental approaches to investigate the basis of processionary, cycloalexic,and head‐vibration behavior of this species. Larvae used both trail pheromones and thigmotactic signals to organize themselves into head‐to‐tail processionary columns. The trail pheromone, produced from the center of the abdomen, remains active for up to 4 h. Processions are not consistently led by particular individuals, but dynamically change over time and often temporarily break into two or more subprocessions. Subprocessions reunite through use of the trail pheromone. We found no evidence that head‐bobbing generates attraction through substrate‐borne or acoustic signals, but this behavior functions in direct contact to excite group activity. Time‐lapse videography used to analyze cycloalexic group formation showed that larvae transition from feeding in a line along the leaf margin to cycloalexic formations on the upper leaf surface via a coordinated back‐up movement that brings the posterior tip of their abdomens into contact. We identify three phases of cycloalexic formation: line‐up, back‐up, and an adjustment phase. Complete assembly can be achieved in as little as 5 s, but often the two phases establishing the basic rosette lasts 5–10 min, while the adjustment phase slowly tightens the group over a period of up to an hour. Collectively these studies present the first documented case of chemical trail marking in a beetle, and provide insight into a remarkable social‐behavioral repertoire convergent in key respects with the better‐studied social caterpillars and sawflies.     

A New Species of the Weevil Genus Dermatodina Faust (Coleoptera,Curculionidae) from Vietnam

Entomological Review - Dermatodina prosvirovi sp. n. from Vietnam is described as new to science. The taxonomic composition of the genus Dermatodina Faust, 1895 is discussed.     

New Taxa and Host Associations of the Weevil Subfamily Ceutorhynchinae (Coleoptera,Curculionidae) from Thailand

A new subgenus of Mecysmoderes Sch., Enzoellus Korotyaev, subgen. n. (type species Mecysmoderes carinatus Faust), two new genera of the tribe Hypohypurini Colonnelli, Siamohypurus Korotyaev, gen. n. (type species S. samuelsoni Korotyaev, sp. n.), Glikmanellus Korotyaev, gen. n. (type species G. rosti Korotyaev, sp. n.) and eleven new species of the weevil subfamily Ceutorhynchinae are described: Mecysmoderes (Memecyderes) sarukhanovi Korotyaev, sp. n. from Thailand, M. (Enzoellus) gressitti Korotyaev, sp. n. from Thailand and Laos, M. (Enzoellus) muratovi Korotyaev, sp. n., Megahypurus oroszi Korotyaev, sp. n., Cyphohypurus suppantschitschi Korotyaev, sp. n., Siamohypurus samuelsoni Korotyaev, sp. n., S. attilai Korotyaev, sp. n., Glikmanellus rosti Korotyaev, sp. n., all from Thailand; G. baloghi Korotyaev, sp. n. from Sri Lanka; G. obrieni Korotyaev, sp. n. and G. louisae Korotyaev, sp. n., both from India. A key to three species of Megahypurus from Thailand is given. Host plants are determined for Megahypurus alexandri Kor. and Glikmanellus rosti sp. n. from Koh Kood Island in southern Thailand, which were repeatedly collected from a tree of the family Rubiaceae.     

Cuticular hydrocarbons of the ectoparasitic wasp Cephalonomia hyalinipennis (Hymenoptera: Bethylidae) and its alternative host,the stored product pest Caulophilus oryzae (Coleoptera: Curculionidae)

Cuticular hydrocarbons of an ectoparasitic wasp attacking two beetle hosts have been identified and examined for the influence of age, gender, mating status, and host on hydrocarbon composition. The 37 wasp hydrocarbons identified consisted of a series of n-alkanes (C16 to C33), 3-, 5-, 9-, 10-, 11-, and 12-methyl alkanes and a series of Z-7 and Z-9 monoenes (C23:1 to C27:1). One C25:2 diene was found. No effects of hydrocarbon composition as a function of age, gender, or mating status were found for the wasps. Wasps reared on Hypothenemus hampei, however, had 12/37 significant abundance differences to those reared on Caulophilus oryzae, although all but one of these differences were for components in less than 2% relative abundance. The C25:2 diene from wasps reared on H. hampei was present in about 10% whereas from wasps reared on C. oryzae it was present in about 2%. The hydrocarbons of one host for this wasp, the coffee berry borer (Coleoptera: Scolytidae), have been previously reported [Howard and Infante, Ann. Entomol. Soc. Am. 89:700-709 (1996)]. The hydrocarbons of the alternative host, C. oryzae (Coleoptera: Curculionidae) consists of n-alkanes (C17 to C31), 3-, 4-, 5-, 7-, 9-, 11-, 12-, 13-, 14-, and 15-methyl alkanes, and a series of dimethyl alkanes of the series 3, 17-; 5, 11-; 5, 17-; 7, 11-; 7, 13-; 13, 17-; and 15, 19-. No unsaturated hydrocarbons were found. No significant differences in hydrocarbon composition were found between male and female C. oryzae. Hydrocarbon patterns of four species of Cephalonomia are compared and shown to be species-specific. The data are discussed in terms of ecological and physiological parameters.     

Mating tactics and courtship behavior inCleogonus rubetra (Fabricius) (Coleoptera: Curculionidae)

Females of the tropical weevilCleogonus rubetra oviposit into fruits of the leguminous treeAndira inermis, and larvae develop in the pulp and seed of these fruits. We hypothesized three alternative tactics by which males might secure matings. By using focal observations of males and by evaluating predictions specific to each hypothesis, we demonstrate that males search within aggregations of conspecifics for receptive females, and upon finding a suitable partner, males mount and perform courtship behavior consisting of stroking the eyes and sides of the female's abdomen. Males also stridulate and emit a sequence of short buzzing sounds. While mounted, males actively prevent rival males from mating with their partner. Males defend their mates for a mean duration of 3.7 h (including copulation). As predicted, paired males were larger than solitary individuals, although the difference was marginally nonsignificant. The overabundance of fruits relative to males, the prolonged period during which females are active, and the probability of last male sperm precedence are factors that may have contributed to the evolution of this female-defense tactic by males. Paired females were significantly larger than solitary females. We observed no competition among females for mates, and the correlation between elytron length of paired males and females was not significant.     

A New Genus of the Weevil Tribe Hyperini Lacordaire (Coleoptera,Curculionidae) from the Middle East

Entomological Review - A new genus Eremohypera gen. n. with the type species Smicronyx alfierii Pic, 1913 from Egypt and Israel and its close relative Eremohypera turkmenica sp. n. from western...     

Little-Known Weevil Taxa (Coleoptera,Curculionidae) Described by V. I. Motschulsky from the Caucasus

Lectotypes of Orthochaetes caucasicus Motschulsky, 1845 and Opitomorphus brevirostris Motschulsky, 1845 are designated. A new combination and new synonymies are established: Anchonidium caucasicum (Motschulsky, 1845), comb. n. (= Styphlus ulcerosum Aubé, 1850, syn. n., = Anchonidium corticeum Faust, 1886, syn. n.); Stomodes Schoenherr, 1826 (= Opitomorphus Motschulsky, 1845, syn. n.); Stomodes tolutarius Schoenherr, 1826 (= Opitomorphus brevirostris Motschulsky, 1845, syn. n.).     

On Findings of Three Western Palaearctic Species of the Weevil Subfamily Entiminae (Coleoptera,Curculionidae) in Yakutia

Entomological Review - Three common Western Palaearctic species of the weevil subfamily Entiminae are recorded from Yakutia for the first time: Otiorhynchus velutinus Germ., O. raucus (F.) and...     

On the Taxonomy and Distribution of the Weevil Genus Anthonomus Germar (Coleoptera,Curculionidae) in the Russian Far East

Entomological Review - Anthonomus (s. str.) alni Kojima et Morimoto, 1994 and A. (s. str.) takahashii Kojima et Morimoto, 1994 are recorded for the first time for Russia. Anthonomus (Anthomorphus)...     

Effects of combining microbial and chemical insecticides on mortality of the Pecan Weevil (Coleoptera: Curculionidae)

The pecan weevil, Curculio caryae (Horn), is a key pest of pecan [Carya illinoinensis (Wangenh.) K. Koch]. Current control recommendations are based on chemical insecticide applications. Microbial control agents such as the entomopathogenic nematode, Steinernema carpocapsae (Weiser) and the fungus Beauveria bassiana (Balsamo) Vuillemin occur naturally in southeastern U.S. pecan orchards and have shown promise as alternative control agents for C. caryjae. Conceivably, the chemical and microbial agents occur simultaneously within pecan orchards or might be applied concurrently. The objective of this study was to determine the interactions between two chemical insecticides that are used in commercial C. caryae control (i.e., carbaryl and cypermethrin applied below field rates) and the microbial agents B. bassiana and S. carpocapsae. In laboratory experiments, pecan weevil larval or adult mortality was assessed after application of microbial or chemical treatments applied singly or in combination (microbial + chemical agent). The nature of interactions (antagonism, additivity, or synergy) in terms of weevil mortality was evaluated over 9 d (larvae) or 5 d (adults). Results for B. bassiana indicated synergistic activity with carbaryl and antagonism with cypermethrin in C. caryae larvae and adults. For S. carpocapsae, synergy was detected with both chemicals in C. caryae larvae, but only additive effects were detected in adult weevils. Our results indicate that the chemical-microbial combinations tested are compatible with the exception of B. bassiana and cypermethrin. In addition, combinations that exhibited synergistic interactions may provide enhanced C. caryae control in commercial field applications; thus, their potential merits further exploration.     

Resistance of Maize Landraces to the Maize Weevil Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

The maize weevil Sitophilus zeamais Motsch. is an important pest of maize that attacks the grain both in the field and during storage. The damage caused by the maize weevil S. zeamais on maize landraces, Amarelo Antigo, Asteca, Caiano, Carioca, and Ferrinho, was evaluated by no-choice tests under laboratory conditions. The commercial varieties Sol da Manh?, BR 106, BR 451, and the synthetics PC 0203 and PC 9903 were evaluated for comparisons with the maize landraces. The parameters evaluated were susceptibility index, number of weevil progeny, development time, weevil progeny dry weight, and grain dry weight loss. The landraces were more susceptible to the maize weevil as compared to the commercial varieties. Based on the cluster analysis, two groups of susceptibility to the maize weevil were observed: one of more susceptible populations formed by local landraces and BR 451, and another less susceptible, with commercial varieties, synthetics, and the landrace Amarelo.     

Repellent Efficacy of Caraway and Grapefruit Oils for Sitophilus oryzae (Coleoptera: Curculionidae)

This study examined the repellent efficacy of six essential oils extracted from caraway, clary sage, grapefruit, strawberry, thyme white, ylangylang, and their related volatile constituents against the adult rice weevil, Sitophilus oryzae using an olfactometer. The caraway and grapefruit oil showed the highest repellent efficacy against the rice weevil at a dose of 10μl. Gas Chromatography-Mass Spectrophotometer analysis revealed caraway oil to be rich in carvone and limonene, and grapefruit oil to be rich in limonene, β-myrcene and α-pinene. When the monoterpene was mixed in equal parts with the caraway and grapefruit essential oils, carvone with limonene in caraway oil demonstrated the highest repellent efficacy (96.7%). Limonene with α-pinene and β-myrcene in grapefruit showed strong repellent efficacy (86.4%) with synergistic effects on the S. oryzae.A mixture of caraway and grapefruit oils, as well as carvone and limonene, can be potent repellents that may be useful for controlling S. oryzae.     

Cuticular hydrocarbons on elytra of the Diaprepes root weevil Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae)

Abstract 1 External gland openings and associated structures on the elytra of teneral and mature Diaprepes root weevils, Diaprepes abbreviatus (L.), were elucidated by scanning electron microscopy (SEM). 2 There were clear differences between teneral, callow adults and fully mature adults. In the field, teneral adults remain in the pupal chamber in the soil until sclerotization of the cuticle is complete or nearly so. 3 Phenotypic variation of the elytra in this species consists of varying patterns and coloration of scaled intervals between a variable number of raised ridges devoid of scales. In addition to being thinner and lighter in colour than fully mature adults, the elytra of teneral adults were devoid of waxy hydrocarbon secretions. 4 External gland openings at the base of each scale were observed on teneral elytra and mature elytra washed with methylene chloride. 5 SEM evidence to document the production of waxy filaments by these glands and partial characterization of these by gas chromatography and mass spectrometry are presented.     

A Record of the Weevil Anthonomus dudkoi Legalov (Coleoptera,Curculionidae: Anthonomini) from Katon-Karagay National Park (South-Western Altai)

Entomological Review - The recently described from the Russian Altai and Kazakh Altai Anthonomus dudkoi Legalov is found in the Katon-Karagay National Park in Eastern Kazakhstan (South-Western...     

Lethal and sublethal effects of rice polishing process on Sitophilus oryzae (Coleoptera: Curculionidae)

The mechanical impact of rice polishingon the rice weevil, Sitophilus oryzae (L.), and the subsequent postpolishing effects associated with rice quality were studied. "Brown" rice (not polished), "White (infest then polish)" rice, and "White (polish then infest)" rice were used with different polishing process intensities and different initial weevil densities. Weevil progeny were more numerous in Brown than in White (infest then polish) or White (polish then infest) rice. Polishing corresponding to a weight loss of 11% in rice generated an immediate mortality of approximately 40%; the subsequent mortality caused by rice quality was also 40% (total >80%). A polishing process corresponding to 14 and 16% of rice weight loss generated a drastic mortality in the weevil population (>95%). The progeny per adult weevil was similar with high and low initial weevil densities. The development of weevil progeny was also delayed by about 1 wk in White (infest then polish) rice compared with Brown rice. Furthermore, weevil adults of the progeny were significantly heavier in Brown than in White (infest then polish) or White (polish then infest) rice.