Monarch butterflies (Danaus plexippus L.) use a magnetic compass for navigation.

Fall migratory monarch butterflies, tested for their directional responses to magnetic cues under three conditions, amagnetic, normal, and reversed magnetic fields, showed three distinct patterns. In the absence of a magnetic field, monarchs lacked directionality as a group. In the normal magnetic field, monarchs oriented to the southwest with a group pattern typical for migrants. When the horizontal component of the magnetic field was reversed, the butterflies oriented to the northeast. In contrast, nonmigratory monarchs lacked directionality in the normal magnetic field. The results are a direct demonstration of magnetic compass orientation in migratory insects.

Mandibular gland components of european and africanized honey bee queens (Apis mellifera L.).

The composition of the five-component honey bee queen mandibular gland pheromone (QMP) of mated European honey bee queens was compared to those of virgin and drone-laying (i.e., laying only haploid unfertilized eggs that develop into males), European queens and Africanized mated queens. QMP of mated European queens showed significantly greater quantities of individual components than all queen types compared, except for a significantly greater quantity of 9-hydroxy-(E)-2-decenoic acid (9-HDA) found in Africanized queens. Glands of European drone-laying queens contained quantities intermediate between virgin and mated queens, reflecting their intermediate reproductive state and age. QMP ontogeny shifts from a high proportion of 9-keto-(E)-2-decenoic acid (ODA) in young unmated queens to roughly equal proportions of ODA and 9-HDA in mated queens. A biosynthetic shift occurs after mating that results in a greater proportion of 9-HDA, methylp-hydroxybenzoate (HOB), and 4-hydroxy-3-methoxyphenylethanol (HVA) production, accompanied by a decreased proportion of ODA. Africanized QMP proportions of ODA and 9-HDA were significantly different from European queens. A quantitative definition of a "queen equivalent" of QMP is proposed for the various queen types, and a standard queen equivalent for mated European honeybee queen mandibular gland pheromone is adopted as 200µg ODA, 80µg 9-HDA, 20µg HOB, and 2 µg HVA.

Maturation of tergal gland alkene profiles in European honey bee queens,Apis mellifera L.

In a series of husbandry and stop-time chemical experiments with honey bee queens, the production of tergal gland alkenes was found to be stimulated by natural mating and not by instrumental insemination. Carbon dioxide, physical manipulation of the sting chamber and vagina, presence of sperm in the spermatheca, egg production, and chemicals transferred via drone semen are demonstrated to not initiate the synthesis of the tergal gland alkenes. The compounds probably do not function as sex pheromones. However, the circumstances and timing of the initiation of production of the tergal gland alkenes strongly suggests a communication role for the compounds within the hive.

Radar detection of drones responding to honeybee queen pheromone.

The response of honey bee (Apis mellifera L.) drones to queen pheromone(s) (either natural from a mated queen, or synthetic from a lure) was recorded using an X-band, ground-based radar. The distribution of drones (insect targets on the radar screen) changed from a scattered distribution to a line concentration (downwind) when the pheromone was released. Displacement within the line concentration was toward the pheromone. This response was seen as far as 800±15 m downwind from a lure with 10 mg of synthetic 9-oxodec-trans-2-enoic acid (9-ODA) and as far as 420±15 m from a mated queen. These studies demonstrate that queen pheromone can be detected by drones at much greater distances than previously believed and illustrate how X-band radar may be used to establish the distances at which insects of similar or larger size respond to pheromones.

Disruptive sexual selection in Colias eurytheme butterflies.

Sexual selection on male pheromone composition in Colias eurytheme (Pieridae) butterflies has the remarkable effect of increasing the variability of this trait. Sexual selection on important traits is generally thought to have a strong stabilizing effect on intraspecific variation of those characters. In this species, however, the male courtship pheromone is highly variable in the relative proportions of its three chemical constituents. Stabilization and/or canalization of this polygenic character in a population is impeded by the disproportionate mating success of males in one portion of the character distribution with alba (white morph) females, and of those in the opposite portion with orange (colored morph) females.

Genetic sources of pheromone variation inColias eurytheme butterflies.

The courtship pheromone ofColias eurytheme butterflies varies greatly among males in both the quantities and relative proportions of its three chemical components [n-heptacosane (C27), 13-methylheptacosane (13MH),n-nonacosane (C29)]. Narrow-sense heritabilities were high for the blend of 13MH and C27 and for the component quantities in one population (Kansas) but were low for the other population tested (Arizona). Genetic correlations between the three components were high in both populations, indicating a substantial degree of additive genetic influence on the component blends. High variability among populations in phenotypic correlations suggests that much of the male-to-male variation in the courtship pheromone may be attributable to environmental or developmental sources. Pheromone phenotypes do not seem to be associated with alba genotype.

Developmental and environmental sources of pheromone variation inColias eurytheme butterflies.

Body size, age, ambient temperature, wing wear, and flight activity were investigated as possible sources of variation in the quantities and relative proportions of the three chemical components [n-heptacosane (C27), 13-methylheptacosane (13MH), andn-nonacosane (C29)] of the male courtship pheromone ofColias eurytheme butterflies. Size of the male has very little influence on the amount of any of the pheromone components present on the wings. Most of the deposition of all three components onto the surface of the hindwing occurs between 3 and 9 hr after emergence from the pupa. 13MH is deposited more rapidly than C27 and C29, and C27 more rapidly than C29. After the first 12 hr posteclosion, the pheromone phenotype of an individual male remains relatively constant through at least 96 hr of age. Experiments showed that none of the three chemicals volatilize to any appreciable extent at temperatures likely to be experienced in the field. The pheromones of actively searching and courting males did not differ from those of less-active feeding and resting males, suggesting that volatilization induced by flight activity is not an important source of pheromone variation. Loss of scales with age does seem to affect pheromone phenotype, but not in a readily interpretable way. Although the quantity of 13MH was lower in worn males than in fresh, C27 was higher.

Neotropical Africanized honey bees have African mitochondrial DNA.

Non-indigenous African honey bees have invaded most of South and Central America in just over 30 years. The genetic composition of this population and the means by which it rapidly colonizes new territory remain controversial. In particular, it has been unclear whether this 'Africanized' population has resulted from interbreeding between African and domestic European bees, or is an essentially pure African population. Also, it has not been known whether this population expanded primarily by female or by male migration. Restriction site mapping of 62 mitochondrial DNAs of African bees from Brazil, Venezuela and Mexico reveals that 97% were of African (Apis mellifera scutellata) type. Although neotropical European apiary populations are rapidly Africanized by mating with neotropical African males, there is little reciprocal gene flow to the neotropical African population through European females. These are the first genetic data to indicate that the neotropical African population could be expanding its range by female migration.

Variation in generation time in Frasera speciosa (Gentianaceae), a long-lived perennial monocarp.

The perennial monocarp Frasera speciosa (Gentianaceae) flowers at a wide range of sizes and ages with consequent variation in generation time (T), net replacement rate (R o) and intrinsic rate of increase (r). Values of r were calculated for hypothetical cohorts composed of individuals flowering at the same age. Maximum rates of r are achieved by plants which flower at the earliest possible age. Although older plants produce more flowers, this increase is not sufficient to compensate for the effect of increased T on r. Few plants in each population flower at the youngest possible age, and for the majority reproduction is delayed, generation times are longer and r lower than achieved by plants flowering at younger ages. Delayed reproduction may be favored by greater seed set, due to pollinator attraction to larger flower stalks, as well as broader seed dispersal which could increase the probability of seedling establishment. Delays greater than those observed may be selected against by decreasing probability of survival, a decrease in the rate of addition of flowers with increasing size, and slower transitions between leaf number classes in larger plants. Staggered reproduction by an individual's offspring, whether environmentally or genetically determined, has the effect of insuring survival in an environment with high variability in pollinator effectiveness (see d set), germination, and seedling establishment.