Hiroe Yasui

Visual and olfactory cues for mate orientation behaviour in male white-spotted longicorn beetle, Anoplophora malasiaca

Olfactory and visual cues were shown to mediate short‐distance orientation in Anoplophora malasiaca (Thomson) (Coleoptera: Cerambycidae). In a laboratory test, more than 80% (n = 42) of males walked straight upward when presented with an untreated surface with a 75° slope. When a freshly killed female was fixed at a short distance (10 cm ahead and 5 cm to left/right) from the starting point, 50% of males (n = 30) were oriented toward the female before direct contact. Similar behavioural responses were observed when female extract was directly applied to the slope or to a glass rod model fixed on the slope. When black, white, and transparent coloured rods with the extract were presented, the orientation response was significantly greater for black than to white and transparent rods, to which only a negligible response was observed.

Ketone components in the contact sex pheromone of the white‐spotted longicorn beetle, Anoplophora malasiaca, and pheromonal activity of synthetic ketones

Two active fractions were found during the isolation of contact sex pheromone of female elytra of the white‐spotted longicorn beetle, Anoplophora malasiaca (Thomson) (Coleoptera: Cerambycidae), in addition to fraction of hydrocarbons that had previously been identified. One fraction was essential to evoke a series of precopulatory behaviors of males toward a glass dummy when coated together with the hydrocarbon blend. The other fraction enhanced this activity when added to the mixture. From the latter synergistic fraction, we isolated five novel compounds and identified them as 10‐heptacosanone, (Z)‐18‐heptacosen‐10‐one, (18Z,21Z)‐heptacosa‐18,21‐dien‐10‐one, (18Z,21Z,24Z)‐heptacosa‐18,21,24‐trien‐10‐one, and 12‐heptacosanone by GC‐MS and NMR analyses. A blend of four of these synthetic ketones, without 12‐heptacosanone, in the ratio and concentration found in female elytra extract (250 : 400 : 1000 : 180 ng FE−1) showed greater synergistic effect than the natural fraction containing the ketones. This effect was canceled out by further addition of 12‐heptacosanone (100 ng FE−1), which was still comparable to the effect of the natural ketone fraction.

Presence of larval and adult diapauses in a subtropical scarab beetle: graded thermal response for synchronized sexual maturation and reproduction

Abstract The white grub Dasylepida ishigakiensis has a 2‐year life cycle and spends approximately 9 months as a nonfeeding larva, pupa and adult on a subtropical island. Evidence is presented indicating that this beetle has two diapauses that appear to synchronize this long life cycle with the seasons. Larvae exposed to 20, 22.5, 25 and 27.5 °C late in the third (last) stadium pupate rapidly except for some individuals kept at the highest temperature. The latter pupate upon transfer to 22.5 °C, indicating that larval diapause is maintained at high temperature but terminates upon transfer to a lower temperature. Pupal development is directly temperature‐dependent in the range 20–30 °C. Adults develop reproductive organs (i.e. the ovary in females and the seminal vesicles and accessory glands in males) rapidly at 15 and 20 °C, whereas those kept at 25 °C take a long time to do so. Ovarian development is completely suppressed at 30 °C but initiated upon transfer to 20 °C. In the laboratory, males with well‐developed reproductive organs mate even with sexually immature females, whereas females with undeveloped ovaries show no sexual behaviour. Although the two diapauses of this species are thermally regulated (i.e. a characteristic commonly expressed by insects in summer diapause), adults of this beetle emerge from pupae late in the autumn and remain in the soil for 2 months. Adult diapause effectively serves to synchronize the time of sexual maturation with the coldest month of the year.

Posticlure: a novel trans-epoxide as a sex pheromone component of the tussock moth, Orgyia postica (Walker)

Abstract A single EAG-active component was found in a pheromone extract from virgin females of the tussock moth, Orgyia postica . This compound named posticlure possesses a trans -epoxy ring and was identified as (6 Z ,9 Z ,11 S ,12 S )-11,12-epoxyhenicosa-6,9-diene by means of GC-MS, 1 H NMR and chiral HPLC analyses, and further chemical derivation followed by the GC-MS analysis. In a field test with the pheromone synthesized stereoselectively, the male moths were specifically attracted to the (11 S ,12 S )-isomer but not to the antipode.

Sesquiterpene Hydrocarbons: Kairomones with a releaser effect in the sexual communication of the white-spotted longicorn beetle, Anoplophora malasiaca (Thomson) (Coleoptera: Cerambycidae)

Summary.We conducted a series of experiments with the white-spotted longicorn beetle Anoplophora malasiaca (Thomson), and its host plant, Citrus unshiu, to examine the origin of the sesquiterpene hydrocarbons (SHCs; including β-elemene, β-caryophyllene, α-humulene, α-farnesene, and several unidentified compounds) that are contained in the elytra of the beetles and act as an attractant. In the laboratory, mechanically wounded citrus branches, as well as those fed upon by A. malasiaca, attracted males more frequently than intact branches. Solid phase microextraction (SPME) and subsequent analyses by gas chromatography (GC) analyses detected measurable SHCs from the air around both mechanically wounded and beetle-infested branches, as well as trace amounts from intact branches. The SHCs were also detected for a certain time from beetles that had fed on the citrus branches, but the amounts decreased rapidly after they were removed from the host. This decrease generally corresponded with a reduction of attractiveness of the beetles in a behavioural assay. Isolated females acquired the SHCs after exposure to, but not upon contact with, other females that had fed on C. unshiu branches. We hypothesize that the citrus SHCs are adsorbed in, retained on, and released from the wax layer of the beetle elytra. Since these compounds are released from branches when beetles feed, they may indirectly signal the presence of beetles to others in the field. The high response rate to SHCs by males is likely representing mate searching behavior. The SHCs act as kairomones with a releaser effect in the communication system of A. malasiaca.

Sexually differentiated functions of female-produced pheromone of the black chafer Holotrichia loochooana loochooana (Sawada) (Coleoptera: Scarabaeidae)

Summary.Both male and female Holotrichia loochooana loochooana (Sawada) (Coleoptera: Scarabaeidae) were attracted with female-produced pheromone, anthranilic acid (2-aminobenzoic acid), in the field. Male chafers were observed to apparently directly locate cotton balls impregnated with 1 to 10 mg of pheromone. In contrast, females never directly oriented to the treated balls but landed 0.2-1.5 m away and exposed their abdominal glands in a calling posture, which occasionally resulted in aggregation of both females and males. This suggested the mating aggregation of this species could be primarily induced by pheromone released by females. A hypothesis for adaptability of female aggregation is proposed and discussed.

Effect of colour on male orientation to female pheromone in the black chafer Holotrichia loochooana loochooana

Summary.Under field conditions significantly more black chafer, Holotrichia loochooana loochooana (Sawada) (Coleoptera: Scarabaeidae) males landed on black and gray sources than white ones containing 10 mg of female pheromone, anthranilic acid. When a broader spectrum of colours was tested the frequency of male landing was intensively proportional to as the lightness of the colour of the lures. These findings demonstrated that mate location by H. l. loochooana males is dependent on both olfactory and visual stimuli of the source. In contrast, female aggregation was not affected by colour.

Anthranilic acid: a free amino‐acid pheromone in the black chafer, Holotrichia loochooana loochooana

Summary. Ether extract of the abdominal gland of female black chafers Holotrichia loochooana loochooana (Sawada) (Coleoptera: Scarabaeidae) induced a series of pre-mating behaviors that included short-distance orientation, mounting and abdominal bending toward females in the laboratory. When the extract was chromatographed on a silica gel column, the activity was eluted with 50% ether in hexane and ether fractions. GC-MS analyses revealed that both the active fractions contained anthranilic acid (2-aminobenzoic acid) as a major compound. When partitioned to basic, acidic and amphoteric fractions, pheromonal activity was observed with the latter two fractions and anthranilic acid was detected in these fractions by HPLC analyses. The amount of anthranilic acid in the female extract was estimated to be ca. 1.3 μg/female. Authentic anthranilic acid induced pre-mating behavior in males of at levels equal to that elicited by the compound in the extract. It also attracted male beetles to the traps in the field.

Identification of novel sex pheromone components from a tussock moth, Euproctis pulverea

Two EAG‐active compounds were found in the solvent extract of abdominal tips of virgin females of the tussock moth Euproctis pulverea (Leech) (Lepidoptera: Lymantriidae), and identified as (Z,Z,Z)‐11,14,17‐icosatrienyl isobutyrate and (Z,Z,Z)‐11,14,17‐icosatrienyl 4‐methylvalerate at 190 and 80 ng female−1, respectively, by means of GC‐MS analyses and chemical derivatization. Esters of n‐butyric acid, n‐valeric acid, n‐hexanoic acid and a methylheptanoic acid were also found at 3, 2, 0.4 and 9 ng female−1 as minor EAG‐inactive compounds. Two active compounds were also detected in the hexane extract of female anal tufts at 17 and 6 ng female−1, respectively. In Okinawa, the binary blend of the synthetic compounds attracted male moths to the sticky traps, but single compounds did not. The significance of these findings in relation to parasitism by Telenomus euproctidis (Hymenoptera: Scelionidae) is discussed.

Do the amount of sex pheromone and frequency of calling behavior in females affect the mate-searching behavior of males in Dasylepida ishigakiensis (Coleoptera: Scarabaeidae)?

The white grub beetle Dasylepida ishigakiensis Niijima et Kinoshita (Coleoptera: Scarabaeidae) is a serious sugarcane pest on the Miyako Islands, Okinawa, Japan. Because this beetle stays underground for most of its lifetime, mating disruption using a synthetic sex pheromone has been suggested as a promising control measure. The amount of pheromone (2-butanol) released by the females is known to decrease drastically as they repeat calling each day. In this study, we determined the response of males to different concentrations of (R)-2-butanol, both in the laboratory and in the field. Males showed typical pre-mating behaviors and they were attracted to (R)-2-butanol even at a concentration 1/100 of the amount typically emitted by a female during the 1st period of calling. We examined whether female attractiveness to males was reduced with the frequency of calling, by counting the number of males attracted to females that had called during zero to five periods beforehand. Our results indicated that a high level of female attractiveness was maintained even after three periods of calling. Based on these findings, we propose that releasing synthetic sex pheromone shortly before the start of the mating season and into the late mating season may be optimal for disrupting the mating of this beetle.