The effects of unilateral antennectomy on the flight behaviour of male Heliothis virescens in a pheromone plume

Abstract .Unilaterally antennectomized Heliothis virescens (F.) males flying close to the central axis of a plume of sex pheromone display no significant differences in behaviour compared to sham-operated males in course angles, track angles, airspeed and groundspeed. This demonstrates that right/left antennal information is not necessary for normal orientation movements in response to pheromone, but rather that it is 'blended' within the moth's central nervous system before pheromone-mediated manoeuvres are made. However, some unilaterally antennectomized moths (36%) make repetitive, asymmetrical, saw-tooth-shaped tracks during pheromone-mediated upwind progress, whereas control moths never make such tracks. Unilaterally antennectomized moths made such tracks on the side of the plume contralateral to the missing antenna. We hypothesize that these occasional asymmetrical tracks in unilaterally ablated males are the result of reiterative asymmetrical pheromone stimulation of a higher probability on track legs going toward rather than away from the long axis of the plume on males with a single antenna remaining on the 'away from axis' side. Combined with a greater propensity for treated moths to lock onto the plume away from the central axis on one side rather than the other, repetitive successive asymmetrical track legs (resulting in a saw-tooth-shaped track) are commonly observed in these moths. Control moths do also make asymmetric successive track legs but they rarely are repeated and thus are not readily observed.     

Response of the sandfly Lutzomyia longipalpis to an oviposition pheromone associated with conspecific eggs

Response of female Lutzomyia longipalpis Lutz & Neiva (Diptera: Psychodidae) to an oviposition attractant and/or stimulant associated with conspecific eggs was investigated in the laboratory. Females of two populations laid significantly higher mean number of eggs on sites with 160 eggs already present than on bare control sites. This response was lost when eggs placed on test sites were previously washed in organic solvents and distilled water. Age of eggs placed on test sites, 1-6 days after being laid, did not seem to affect the oviposition response of the females. Comparing effects of different numbers of eggs, positive responses were obtained when 80, 160 or 320 eggs were placed on test sites. No significant differences between mean egg numbers laid on test sites and controls were detected when batches of only 20 or 40 eggs were used.     

Deposition and longevity of oviposition-deterring pheromone in the cabbage seed weevil

Abstract The cabbage seed weevil ( Ceutorhynchus assimilis Payk.) lays eggs singly into pods of oilseed rape ( Brassica napus L.) through punctures bored with the mouthparts, preferring pods not recently used for oviposition. A simple new choice test has been used to test individual components of egg-laying behaviour for their effect on oviposition site selection. It is confirmed that an oviposition-deterring pheromone (ODP) is deposited during abdomen brushing of the pod which follows egg-laying. Neither pin punctures, weevil feeding punctures, oviposition punctures nor eggs had any deterrent effect. Pods walked on by female weevils were not avoided by those laying eggs. Observations suggest that the ODP is sensed by contact chemoreceptors on the antennae. The deterrent effect lasted only 1–2 h. The implications of these findings on the adaptive significance of the pheromone and its possible use in pest control are discussed.     

Development of mating disruption for control of pine sawfly populations

Mating disruption of the pine sawflyNeodiprion sertifer (Geoffroy) (Hymenoptera: Diprionidae) was strongly indicated by reduced male trap catches in pine plantations permeated with the sex phermone, (2S, 3S, 7S)-diprionly acetate. The trap catch reduction was 95 to near 100% when dispensers every 10 m were used, giving a total release of about 3 mg per hectare and day. Two mg of pheromone per cotton roll dispenser maintained low catches for the whole season (about 2 months) without any renewal of disruption dispensers. Anerythro-mixture was as effective as the pure pheromone isomer. The effects of the experiments on population density and sex ratio were not possible to investigate, due to a general collapse of the population, also outside experimental plots, the year after the experiments.     

Predator attack motivation influences the inspection behaviour of European minnows

Predator inspection behaviour at different levels of attack motivation (attack status of the predator) was investigated in European minnows Phoxinus phoxinus from a population sympatric with pike Esox lucius , during controlled laboratory experiments. Shoals of minnows performed more predator inspections and formed larger inspection group sizes shortly after an attack by a pike. After inspection, minnows returned to the safety of the main shoal, regardless of predator motivation. Minnows which inspected last-before and first-after a strike by a pike modified their behaviour after inspection; they reduced feeding, increased shoaling, flicked their dorsal and pectoral fins and skittered. This behaviour signified alarm and appeared to reflect the severity of the threat posed by the predator at the time of inspection. Fish that had inspected when the pike displayed low attack motivation did not modify their behaviour after inspection to reflect alarm. Information concerning the attack motivation of the predator is probably transferred passively throughout the shoal by changed inspector behaviour and by inspection rate. These data demonstrate that: (1) minnows modified their behaviour after inspection to reflect a predator's attack motivation; and (2) minnows which inspected immediately before a strike appeared to anticipate the future attack and modified their behaviour accordingly.     

Influence of virgin queen honeybees (Apis mellifera) on queen rearing and foraging

ABSTRACT. Virgin queens are as effective as mated laying queens at inhibiting colonies from rearing queens but not from producing queen cell cups. Colonies without brood produce fewer queen cell cups than similar colonies that have brood. Colonies without queens forage much less and collect less pollen than with either a mated or virgin queen. Colonies with virgin queens forage as much as those with mated queens but collected less pollen.     

Ants adjust their pheromone deposition to a changing environment and their probability of making errors

Animals must contend with an ever-changing environment. Social animals, especially eusocial insects such as ants and bees, rely heavily on communication for their success. However, in a changing environment, communicated information can become rapidly outdated. This is a particular problem for pheromone trail using ants, as once deposited pheromones cannot be removed. Here, we study the response of ant foragers to an environmental change. Ants were trained to one feeder location, and the feeder was then moved to a different location. We found that ants responded to an environmental change by strongly upregulating pheromone deposition immediately after experiencing the change. This may help maintain the colony''s foraging flexibility, and allow multiple food locations to be exploited simultaneously. Our treatment also caused uncertainty in the foragers, by making their memories less reliable. Ants which had made an error but eventually found the food source upregulated pheromone deposition when returning to the nest. Intriguingly, ants on their way towards the food source downregulated pheromone deposition if they were going to make an error. This may suggest that individual ants can measure the reliability of their own memories and respond appropriately.