New aspects of the biology of the Melanesian rfhinoceros beetle Scapanes australis (Col., Dynastidae) and evidence for field attraction to males

Scapanes australis is a major coconut pest, endemic in Papua New Guinea. Early in the night, males placed singly into artificial galleries made in young coconut palms exhibited a sex specific calling behaviour for 1 to 1.5 h. Coming to the gallery entrance, they raised the abdomen and the hind legs, the head lowered inside the gallery, and emitted a liquid secretion, rhytmically smeared by crossing the legs. Females which did not behave so, were very mobile. The adult flying period coincided with the male calling behaviour. In field assays with caged insects on coconut palms, attraction of both sexes to males was evidenced when they were calling. Males fought for gallery possession at a male arrival. No aggression but mating was observed with arriving females, which proved not to have developed oocytes. The strong male attractionwas confirmed using automatic traps, baited with one lived male in a sugarcane piece. Male were assumed to release an aggregation pheromone. Further studies are underway to identify the putative pheromone.     

Ecology of baculovirus-infected and healthy adults of Oryctes rhinoceros (Coleoptera: Scarabaeidae) on coconut palms in the Philippines

Abstract.

• 1 Males and females of Oryctes rhinoceros (L.), a serious pest of coconut palms, congregate in decaying coconut trunks to mate, oviposit and prepare the wood for the young larvae. A baculovirus disease is often transmitted from beetle to beetle in this environment and transmission to and from larvae probably also occurs.
• 2 Young beetles are mainly found feeding on palms, where they also frequently contract the virus disease, presumably through mating with diseased partners.
• 3 Monitoring beetle populations in the Philippines with attractant traps and by collections from palms showed seasonal fluctuations which were often inversely correlated with the incidence of the virus disease. Disease prevalence matched closely the proportion of females in the population. Possible explanations for this correlation and for the seasonality of the disease prevalence are outlined.

     

Effects of meadow suitability on female behaviour in the alpine butterfly Parnassius smintheus

Abstract  1. Many butterfly populations persist in networks of naturally fragmented habitat patches. Movement and reproductive decisions made by adult females are critical to the persistence of these populations because colonisation of extinct habitat patches in the network requires emigration of fecund adult females from their natal meadow and their subsequent establishment in the extinct patch.
2. Movement and oviposition behaviours of mated Parnassius smintheus females released in suitable meadows (a good- and a poor-quality meadow) and an unsuitable meadow were compared, to determine whether adult females consider meadow suitability for their offspring despite frequent oviposition events off the larval host plant.
3. Bootstrap and correlated random walk analyses of female step lengths and turn angles demonstrated that females flew more randomly in the unsuitable meadow than in the suitable meadows. Although females tended to turn the sharpest angle between landing sites in the good-quality meadow, and fly the smallest distance between landing sites and displace the smallest distance from the release site in the suitable meadows, no significant differences were detected in turn angle, step length, and dispersal rates between suitable and unsuitable meadows.
4. Results from female flight observations and a caged oviposition study suggest that females lay significantly more eggs in suitable habitat than in unsuitable habitat despite not ovipositing on the host plant, and support the above findings.
5. Movement and oviposition behaviours of adult female P. smintheus promote their retention within meadows that can support their offspring.     

Avoidance of egg parasitism through submerged oviposition by tandem pairs in the water strider, Aquarius paludum insularis (Heteroptera: Gerridae)

Abstract.  1. Females of the water strider Aquarius paludum insularis (Motschulsky) (Heteroptera: Gerridae) carry males on their backs and oviposit under water after copulation. This study focuses on the benefit  A. paludum insularis receives by ovipositing in tandem.
2. Males guarded females in tandem through to the end of oviposition in 85% of copulations. Females in tandem dived deeper than single females, and the density of A. paludum insularis eggs increased with water depth. The proportion of eggs parasitized by a scelionid wasp, Tiphodytes gerriphagus Marchal (Hymenoptera: Scelionidae) decreased with increasing water depth.
3. These results suggest that during oviposition guarding by males is beneficial for females, because it enables pairs to dive and lay eggs deeper and in oviposition sites where the risk of egg parasitism is lower.     

Radio-telemetric monitoring of dispersing stag beetles: implications for conservation

Migratory movements of the endangered stag beetles Lucanus cervus (18 males, 38 females) were monitored radio-telemetrically for three reproductive periods (2003–2005). The aim of the study was to estimate the migratory range of free-ranging individuals as a measure of connectivity among neighbouring populations for future conservation measures. Miniature transmitters of c . 350 mg (battery life: 10–15 days) were attached externally to the pronotum. Transmitter/beetle mass ratio was 12.8% on average (7.1–28.0%). Male dispersal behaviour consisted of frequent flights directed to sites with reproductive females and rarely of on-ground movement. Total displacement distance recorded was up to 2065 m, the maximum distance of a single flight being 1720 m. Flights always began at elevated structures such as trees and shrubs and took place in an air temperature range of 11–27°C. Within this range, temperature did not influence flight distance. Female dispersal behaviour consisted mostly of a single flight, followed by mating and consequent ground movements towards oviposition sites. Total displacement distance recorded was up to 762.6 m, the maximum distance of a single flight being 701 m. Climatic constraints of flights were the same as in males. Modelling the dispersal behaviour suggests that about 1% of males are capable of maintaining gene flux among nest sites within a radius of about 3 km. However, the colonization of new nest sites depends on the dispersal ability of females and amounts to less than 1 km. Thus, isolated populations (distance to the next population greater than 3 km) have an increased probability of local extinction.     

Flight activity ofProstephanus truncatus (Horn) (Coleoptera: Bostrichidae) in relation to population density,resource quality,age, and sex

Higher flight activity has been observed in aged, high-density cultures ofProstephanus truncatus (Horn) (Coleoptera: Bostrichidae), but adults in new, lowdensity culture jars showed less flight activity. In order to understand this change in behavior, the effects of population density, age, resource quality, and sex on the flight ofP. truncatus were studied in a wind tunnel. While an immediate density on the release platform had no significant effect on flight, beetles from high-density cultures were more inclined to fly than those from low-density cultures. Resource quality exerted a major influence on flight; insects in food suitable for boring and oviposition seldomly exhibited flight, however, when food was absent or of inferior quality for boring and oviposition, the dominant behavior was flight. Also, insects maintained for a week in food suitable for boring and oviposition were less ready to fly than those maintained in food unsuitable for boring and oviposition. The optimum age range for flight activity was before the peak of reproduction and insects rarely flew before 4 days or after 32 days of emergence. There were no significant differences between the flight activity of males and that of females. Based on these results, we conclude that age and resource quality are major influences on the flight activity ofP. truncatus and a hypothesis is proposed in which reproductively active male and female beetles disperse from habitats of low resource quality to those that support their reproductive behavior. The practical implications of these results and the possible role of the male-produced aggregation pheromone are discussed.     

Alternative mate-finding tactics in a non-territorial damselfly (Odonata: Coenagrionidae)

Males of the non-territorial damselfly Enallagma hageni have two alternative tactics for finding mates: (1) they search the banks of the pond for unmated females (searching tactic), or (2) wait at oviposition sites for females that resurface prematurely from underwater oviposition (waiting tactic). Although the searching tactic yielded more fertilizations than the waiting tactic, for time invested, the waiting tactic became increasingly successful later in the reproductive season due to changes in female oviposition behaviour. The two tactics can be maintained in the population because males can mate by the waiting tactic during the afternoon when few females are available to searchers. Among males visiting the breeding site an equal number of times, males mating by a mixture of tactics were as successful as males mating only by the main tactic. Because marked males were found to use both tactics, these behaviours are interpreted as evidence of behavioural plasticity within individuals, representing one conditional evolutionary strategy.     

Field observations of mating,oviposition, and feeding behavior ofAnticarsia gemmatalis (Lepidoptera: Noctuidae) in a soybean field

The temporal occurrence and frequency of mating, oviposition, and feeding of wild velvetbean caterpillar moths, Anticarsia gemmatalis,in a soybean field (Glycine max)were documented. Mating occurred predominately during the first 4 h after sunset and primarily on leaflet bottoms. Oviposition was concentrated within the first 6 hr after sunset. Eggs were laid singly, and in areas of high trichome density, on leaflets, pulvini, and petioles. Feeding occurred primarily at night, with most males feeding during the first half of the night and females during the second half. Males and females shared some food sites but others were visited strictly by males.     

Male perch selection and the mating system of the robber fly,Promachus albifacies (Diptera: Asilidae)

We studied the activity and spatial distribution of the robber fly,Promachus albifacies, in a desert grassland habitat in central New Mexico. Late in the season males spent most of the daytime on or near cholla and yucca plants that had dead stems or dead flower stalks at least 1 m high. Of the three hypotheses (thermoregulation, foraging, mate encounter site) considered as explanations for this distribution, the mate-encounter-site hypothesis was best supported. Plants used by females as oviposition sites were the focus of male activity. Males perched within or near these plants and attempted copulations with females detected nearby. Most matings were initiated at these locations. Seasonal changes in male and female activity also supported the mate-encounter-site hypothesis. Early in the season, females spent little time ovipositing, and predictably, males spent little time on or near these plants. Such a mating system may be described as resource defense polygyny, since males acted aggressively toward one another at oviposition sites even when females were not present. However, the short tenure of males at these sites is suggestive of scramble competition polygyny. We discuss possible reasons why this particular mating system has evolved.     

Attraction of the sexes inFormica lugubris Zett (Hymenoptera: Formicidae)

Summary Sexuals ofFormica lugubris fly to mating places, where females attract males by using a sex pheromone. Females collected on the nest surface before departing on a mating flight are much less attractive than those collected on the mating place after the mating flight, suggesting that the mating flight triggers the release of the sex pheromone. Olfactory cues are essential for males to locate females while they patrol. Males probably use visual cues to locate females once they have alighted nearby them. Males are also attracted by aggregations of other males on the ground, probably because one or several females are likely to be close to male aggregations.     

Flight initiation in the egg parasitoid Trichogramma minutum: Effects of ambient temperature, mates, food, and host eggs

Emergence, preening, and flight initiation were studied in laboratory-reared Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae). Male parasitoids emerged first and flew before females. When both sexes were present in flight cylinders, female parasitoids flew before males. Flight propensity in males was negatively related to the number of emerging females, while flight propensity in females was independent of the number of males present. Ambient temperature significantly affected the propensity and timing of flight; between 70–80% of the parasitoids flew at 25 and 30 °C while less than 4%, mostly males, flew at 20 °C. No flights were observed at 15 °C. The presence of fresh host eggs caused a reduction in the proportion of female parasitoids that flew and a delay in the time to flight for the females that did fly. The presence of food increased the flight propensity of female parasitoids, but did not affect the timing of flight. The relationship between flight behaviour and the efficiency of mass-reared Trichogramma is discussed in terms of its importance for inundative release programmes.     

Flight orientation behavior of Ooencyrtus nezarae (Hymenoptera: Encyrtidae), an egg parasitoid of phytophagous bugs in soybean

We conducted field experiments to examine flight orientation behavior of Ooencyrtus nezarae Ishii, an egg parasitoid of soybean feeding bugs, using sticky traps with synthetic aggregation pheromones of the host, Riptortus clavatus (Thunberg). Experiments were conducted in plots either containing a soybean field or not containing one. When the traps were suspended at heights of 0.5, 1.5 and 3.0 m above a soybean field in Kobe, O. nezarae females were most frequently caught in the 0.5 m traps. In an open field on the same campus where the vegetation was predominantly tall goldenrod, females were more frequently trapped at 1.5 or 3.0 m. In a soybean field in Kumamoto, females were most frequently trapped in the 0.8 m traps, compared to traps placed at 2.0, 4.0 and 6.0 m. In an oat field in the same area, females were trapped most frequently at heights of 0.8 and 2.0 m. Unlike females, only a small number of males were trapped in the fields in both areas. The result that O. nezarae females were caught in traps at higher positions in non‐host habitats than in soybean fields probably reflects differences in host searching behavior in or movement between the habitats. In host habitats, females mainly walk on the plants or fly within the plant canopy to search for hosts. In non‐host habitats, females may not intensively search for hosts within the plants, and directly respond to host pheromones in the traps at heights equal to or a little higher than the plant canopy.     

Alternative reproductive routines in a small fly, Puliciphora borinquenensis (Diptera: Phoridae)

Abstract. 1. Puliciphora borinquenensis (Wheeler), a very small phorid fly in which the female is apterous, breeds in small patches of decomposing organic matter such as dead insects. 2. Females leave the shelter of oviposition sites during the afternoon and ‘parade’ in exposed places making vigorous abdominal pumping movements which probably help to disperse a pheromone. 3. Males exhibit one of four reproductive routines. In the first they perform rapid sequences of stationary copulations with different parading females, achieving rates of 0.66 females min^-1 for periods of 30min (Al). In the second (A2) they wait on oviposition sites and grab non-parading females which have recently arrived. 4. In the third routine a male airlifts a parading female in copula to an oviposition site (Bl); in the final type of routine, females are airlifted and then deposited randomly when oviposition sites cannot be found (B2). 5. Males are able to learn the location of oviposition sites and this enables them to transport large numbers of females (up to thirty-three per male) to sites at a high rate (0.5 females min^-1). 6. Immediately a female is released after a B routine, the male follows her closely for up to 10s. This is thought to represent a phase of non-contact guarding, suggesting the occurrence of sperm competition. 7. Individual males persist with either A or B routines for long periods (c. 30 min), but they are able to switch between routines. 8. Young males (< 27 h after emergence) carry out A routines 18 times more commonly than B routines, whereas older males carry out A routines only 1.6 times more commonly than B routines. The choice between A and B routines in older flies does not depend on male or female density. 9. Males benefit from B routines because the eggs they fertilize are likely to reach oviposition sites, but they pay a considerable energy cost. A routines, on the other hand, are energetically cheaper, but mated females are less likely to reach oviposition sites unless they are subsequently transported by B males. An A male can then benefit provided his sperm are not completely displaced by the second male.     

Use of Radio Telemetry for Studying Flight Movements of <Emphasis Type="Italic">Paysandisia archon</Emphasis> (Lepidoptera: Castniidae)

The moth Paysandisia archon is an invasive species that infests palm trees in the Mediterranean Basin. The immature stages occur exclusively inside the palm crown, whereas adults fly to mate and locate a new host plant. Here, we describe the use of small radio transmitters (0.27 g) for tracing the movements of P. archon adults. We report the first successful use of radio telemetry to track flight distances and space use of a flying moth. Our study was carried out using 11 tagged moths released on the Maguelone Peninsula in southern France. Although the males were successfully tracked within a restricted area, estimated at 4 ha, most of the tagged females immediately flew distances over 500 m, disappearing beyond the maximum detection range of the 30 ha study area. Flights for mating, resting and, likely, oviposition covered distances of 11.6 m to 224 m in males and 16.8 m to >500 m in females. We found evidence that both sexes are active during the warmer temperatures of the day. In contrast, the moths were inactive when the relative humidity was high. Moreover, the P. archon moths do not seem to reside on the host palm trees. Our data show a high mobility of females, which may be responsible for the spread of the first recorded Castniidae in France by laying eggs far from the palm trees where they emerged.     

Upwind flight by the cabbage root fly, Delia radicum

ABSTRACT. In fourteen releases, most female D.radicum (L.) (Diptera, Anthomyiidae) flew upwind or at an angle to it of less than 77° regardless of the presence of host-plant odour. Females ready to lay eggs flew upwind without prior stimulation by odours from either a host crop or a trap releasing up to 3 ml/day of the attractant allylisothiocyanate. Upwind flight was more pronounced in flies from a diapause than from a continuous, non-diapause culture. Males from the non-diapause culture dispersed upwind and downwind in more or less equal numbers; old males flew mainly downwind. But, like the females, most males from the diapause culture flew upwind. Long-distance, odour-modulated anemotaxis did not appear to be used to locate distant host crops by either sex. It is concluded that the distances of insect orientation to plant odours recorded to date are only of intermediate range, and that long-range orientation to the odours of a host-plant still has to be proven. It is suggested that host-plant volatiles are involved not only in the final stage of host location but also in the first, and probably most important stage of host selection whilst the insect is still in flight.     

Seasonal flight activity of Platycerus caprea (Coleoptera, Lucanidae) in the Moravskoslezské Beskydy Mts (Czech Republic)

The seasonal flight activity of Platycerus caprea was studied at two sites in the Moravskoslezské Beskydy Mts in 2002–2004 using bark beetle pheromone traps of Theysohn® type. Platycerus caprea occurred at altitudes of 400 m up to 1200 m a.s.l. Seasonal flight activity in both males and females started at the beginning of May and continued until mid-June. At lower altitudes (up to ca 900 m a.s.l.), adults flew in the first half of May, at altitudes about 1000 m a.s.l. in the second half of May and in the highest sites more than 1200 m a.s.l. in the first half of June.     

Sex biased intra-tree oviposition site selection and larval foraging behavior of a specialist herbivore

Heterogeneity in the quality of oviposition and feeding sites within plants can significantly influence the distribution and abundance of herbivorous insects, but remains poorly understood. Field surveys and a manipulative study were conducted to evaluate the influence of variation within the crown of black spruce, Picea mariana (Mill.) B.S.P. (Pinaceae), on adult oviposition and larval feeding behavior of yellowheaded spruce sawfly, Pikonema alaskensis Rohwer (Hymenoptera: Tenthredinidae). Most eggs were laid in the mid to lower crown of 1.5–2 m tall trees. However, most of the few eggs that were laid in the upper crown (i.e., whorl 2) were female. Fourth and fifth instars dispersed acropetally, from the mid and lower to the upper crown, causing high defoliation in the upper crown. Late-instar females were generally more abundant than males on the leader, the most apical shoot on a tree where eggs and early instars rarely occurred, strongly suggesting that more females than males disperse acropetally. This hypothesis was supported in a manipulative experiment, where only 15–20% of larvae in all-male broods, but almost three-quarters of larvae in mixed broods, dispersed to the upper crown. To our knowledge, this is only the second study to explicitly demonstrate preferential allocation of progeny sex through oviposition site selection by a herbivorous insect, and the first study to unambiguously demonstrate sex-biased dispersal by the juveniles of an insect whose adult females can fly. This study emphasizes the important role of intra-plant variation in shaping both oviposition site selection and the dispersal behavior of juvenile phytophagous insects within their hosts, and suggests that sex-biased foraging behaviors may be necessary for some insects to accommodate the respective needs of immature females and males within heterogeneous host plants.     

Sex ratio and female sexual status of the coconut pest, Oryctes monoceros (Coleoptera: Dynastidae), differ in feeding galleries and pheromone-baited traps

Oryctes monoceros is a serious coconut pest, causing up to 40% damage in tropical Africa. Synthetic aggregation pheromone, ethyl 4-methyloctanoate, has been used to lure adults to traps. Traps with pheromone plus decaying palm material captured a high proportion of males. This raises the question whether individuals, which damage palms are receptive to the pheromone. We studied the sex ratio of the insects feeding on coconuts and those attracted to pheromone traps. Sixty two percent of adults from feeding galleries on living coconut palms were females. Pheromone with rotting palm material lured 43% females. To investigate the reasons for this difference, we compared the reproductive system of females lured to the odour traps or feeding in coconut galleries, or present in old rotting stems. Ninety six percent of the females trapped by pheromone had mated, and were sexually mature. In the galleries on living palms, 46% of females were immature, and 24% had not mated. In old rotting stems where eggs are laid and larvae develop, a mixture of 52% mated and 48% virgin females was found. Therefore, the pheromone together with the odour of rotting coconut stems signals a reproduction site to beetles, particularly mature females. In practice, the pheromone-baited traps will help in reducing the dissemination of gravid females, but will not affect directly the numbers of immature ones attacking palms. Our results show that when using pheromones for monitoring or controlling insects, the physiological status of the insects may have unexpected effects on the outcome.     

METHOPRENE INFLUENCES REPRODUCTION AND FLIGHT CAPACITY IN ADULTS OF THE RICE LEAF ROLLER,Cnaphalocrocis Medinalis (GUENỂE) (LEPIDOPTERA: PYRALIDAE)

Juvenile hormone (JH) influences many aspects of insect biology, including oogenesis‐flight syndrome tradeoffs between migration and reproduction. Drawing on studies of many migratory insects, we posed the hypothesis that JH influences migratory capacity and oogenesis in the rice leaf roller, Cnaphalocrocis medinalis. We treated adults moths (days 1, 2 and 3 postemergence) with the JH analog (JHA), methoprene, and then recorded the influences of JHA treatments on reproduction. JHA treatment on day 1 postemergence, but not on the other days, shortened the preoviposition period, although JHA did not influence total fecundity, oviposition period, or longevity. We infer day 1 postemergence is the JH‐sensitive stage to influence reproduction. Therefore, we treated moths on day 1 postemergence with JHA and recorded flight capacity, flight muscle mass, and triacylglycerol (TAG) accumulation. JHA treatments did not influence flight speed, but led to reductions in flight durations and flight distances. At day 3 posttreatment (PT), JHA‐treated females flew shorter times and less distance than the controls; JHA‐treated males, however, only flew shorter times than the controls. JHA treatments led to reductions in flight muscle mass in females at days 2–3 PT and reductions in TAG content in females at day 3 PT, but, these parameters were not influenced by JHA in males. These findings strongly support our hypothesis, from which we infer that JH is a major driver in C. medinalis oogenesis‐flight syndrome tradeoffs. Our data also reveal a JH‐sensitive stage in adulthood during which JH influences the oocyte‐flight syndrome in C. medinalis.     

Diel timing and frequency of sugar feeding in the mosquito Anopheles gambiae, depending on sex, gonotrophic state and resource availability

Little is known about the sugar-feeding behaviour of equatorial Africa's principal vector of malaria, Anopheles gambiae Giles (Diptera: Culicidae). It is suspected to feed on plant sugar infrequently, but possibly the timing depends on environmental circumstances, and males may differ markedly from females. These points of uncertainty were clarified in the laboratory, by monitoring both diel and longterm sugar-feeding activity in both sexes. Males fed on sugar in a nocturnal diel rhythm closely approximating non-specific flight activity. Female diel sugar-feeding patterns resembled published rhythms and cycles of host seeking. Males sugar fed nightly at an average frequency of about twice per night, sustained over 17 days. This was substantially higher than the sugar-feeding frequency of females that were allowed both blood and oviposition sites every night: they averaged about one sugar feed in every 4 nights. These females fed on sugar between gonotrophic cycles, after eggs were mature but before the next bloodmeal. They did not sugar feed during the 2 days after blood feeding, while blood was being digested and the eggs developed. A slight delay in the availability of either the oviposition site or blood led to an increase in female sugar-feeding frequency: they averaged more than once per night until the delayed resource was made available. These observations support the conclusion that sugar feeding is a normal part of the biology of both sexes of An. gambiae.