Yoshiaki Obara

Studies on the mating behavior of the White Cabbage Butterfly, Pieris rapae crucivora Boisduval

Summary1.The sexual behavior of this species is initiated by the males approach to the female, which is released by the specific wing color of the female.2.This specific female wing color, probably distinguishable from that of the male to insect eyes but not to those of humans, contains a near-ultra-violet component of 380 to 400 mμ, as an essential agent for the release of the sexual activities of the male.3.The operation of the later stages of the sexual behavior, as well as its initiation phase, depends almost exclusively on the optical properties of the female wing color.4.Olfaction probably plays no rôle in any process of the sexual behavior.5.The markings on the wing play no essential rôle in eliciting the sexual response in males, and accuracy in the shape and size of the wing is not indispensable for the operation of the sexual behavior in the male.6.No particular courtship or rituals are recognized in any process of the sexual behavior.7.Discussion is presented in connection with the specific change in hue of the female wings according to seasonal or climatic factors, which results from the fact that ultra-violet light is easily absorbable by the atmosphere or clouds. The significance of this hue change as a signal in intraspecific communication is also discussed.8.Such social behaviors as swarming, “flutter response” and so on are discussed in terms of optical phenomena especially of the near-ultra-violet reflection, which constitutes the main cue in eliciting sexual responses in the male.

Initial Mate Recognition in the British Cabbage Butterfly, Pieris rapae rapae

Abstract Visual features of the wing color, with special reference to the UV (ultraviolet) color, of the British subspecies of the cabbage butterfly, Pieris rapae rapae and its mating behavior were investigated. Both sexes of the British subspecies were found to lack UV color and differed only slightly in color in the visible color range, with female wings more yellowish. It follows that they show only slight sexual dimorphism in wing color. It was shown that the initial mate recognition was mediated visually, based on the wing color. Males discriminated between the sexes visually, but only marginally and were occasionally observed to approach other males mistakenly. The resting males approached by female-searching males displayed a flutter response, deterring the approaching males from attempting to copulate with them; i.e. it functioned as “mechanical isolation mechanism” against maladaptive copulatory attempts between males. The results are discussed in terms of the comparative ethology of the mating behavior with that of the Japanese subspecies. It is suggested that the British subspecies is ancestral to the Japanese subspecies.

Cooperative foundation of colonies by unrelated foundresses in the ant Polyrhachis moesta

SummaryField studies ofPolyrhachis moesta revealed that colonies were facultatively founded by more than one queen, even though each established colony was inhabited by only one queen with her workers. In pleometrotic colonies, it was found that cofoundresses frequently exhibited cooperative behaviors, including trophallaxis. The results of DNA fingerprinting showed that multiple foundresses were not genetically to one another. It seems that they aggregate randomly and independently of their relatedness. A discussion of the reasons why foundresses ofP. moesta do not aggregate preferentially with genetically related females.

Mate refusal hormone in the cabbage white butterfly

1. War, C.-K., John, T., Towers, G.H.N. : J. Ethnopharmacol. 2, 279 (1980) 2. Arnason, T., et al. : Can. J. Microbiol. 26, 698 (1980) 3. Wat, C.-K., et al.: J. Nat. Prod. 42, 103 (1978) 4. Bohlman, F., Burkhardt, T., Zdero, C.: Naturally Occurring Acetylenes. New York: Academic Press 1973 5. Jones, E.R.H., Thaller, V., in: The Chemistry of the Carbon-Carbon Triple Bond, p. 621 (Patai, S., ed.). New York: Wiley 1978 6. Weiss, U., Edwards, J.M. : The Biosynthesis of Aromatic Compounds. New York: Wiley 1980 7. Butcher, D.N., in: Plant Cell, Tissue, and Organ Culture, pp. 668, 703 (Reinert, J., Bajaj, Y.P.S., eds.). New York: Springer 1977 8. Jente, R.: Tetrahedron 27, 4077 (197i); Setia, B. : Thesis Univ. MOnster 1978; Ichihara, K., Noda, M.: Biochim. Biophys. Acta 487, 249 (1977) 9. Tietjen, K., Matern, U.: Abstr. Phytochem. Soc. North Am. Newslett., July, p. 12 (1981) I0. Schenk, R.U., Hildebrandt, A.C. : Can. J. Bot. 50, 199 (1972) 11. Weete, J.D., Venketeswaran, S., Laseter, J.L. : Phytochemistry 10, 939 (1971)

Delayed mating and its cost to female reproduction in the butterfly,Eurema hecabe

The timing of mating of females under semi-natural condition, male ejaculate production and their effects on female fecundity were examined inEurema hecabe. Age of the first mating of females varied, and the number of matings increased with age. Male spermatophore production depended on age and body mass. The spermatophore mass at the second mating depended only on the interval between the first and second matings. The timing of the first mating and the spermatophore mass did not affect female fecundity. The timing of mating of females relative to the role of male spermatophores in female fecundity and male mating strategy are discussed.

A game model for the daily activity schedule of the male butterfly

A game model is developed of the daily schedule of matesearching activity by male butterflies, assuming that each male maximizes his expected mating success given a limited total time for mate search. The model predicts that (1) in the early morning, no male is active even though many females are emerging; (2) at a critical time, many males suddenly become active; and (3) the males maximum activity occurs after the peak female emergence and before the peak capture efficiency. The inverse problem is also analyzed, in which the temporal pattern of capture efficiency is estimated from the knowledge of male activity and female emergence, assuming the evolutionarily stable strategy (ESS) condition. The model is then applied to data from a cabbage white butterfly (Pieris rapae crucivora) population and predicts that (1) females remain unmated for several hours on average after emergence, and (2) the male s capture efficiency is rather low and increases significantly with time during the morning.

The Influence of Air Temperature and Sunlight Intensity on Mate-Locating Behavior of Pieris rapae crucivora

Abstract It is considered that the mate-locating behaviors of ectothermic insects are constrained by the ambient thermal conditions, since the flight ability depends on the body temperature. However, since ecological factors also influence the mating behaviors, the flight ability would not necessarily determine the time schedule of male mate-locating flight. To reveal how the ambient thermal conditions influence the mating behaviors, we investigated the association of air temperature and sunlight intensity with the diurnal schedule of female-searching behavior in male P. rapae crucivora. In the early morning, the proportion of female-searching males to basking males increased as the air temperature and sunlight intensity increased. The air temperature was also associated significantly with the diurnal schedule of male female-search on 7 of 8 observation days. The number of female-searching males reached the peak when the air temperature was between 24 and 29°C. On the other hand, the sunlight intensity did not account for the diurnal schedule of male female-search. The associations between the sunlight intensity and male female-search were not consistent among different days. When the air temperature was roughly constant, however, the sunlight intensity was correlated significantly with male activity of female-search. The regression of male activity of female-search as a function of sunlight intensity was improved, when it was assumed that the sunlight intensity influenced male behaviors with a delay of 1 to 4 minutes, and when it was assumed that the mean intensity of sunlight for 1 to 9 minutes influenced male behaviors.

Time allocation to the reproductive and feeding behaviors in the male cabbage butterfly.

Abstract Individually marked males of Pieris rapae crucivora, were observed to determine how they allocate time to reproduction and feeding. Males were found to alternately feed and search for females. This manner of time allocation persisted throughout the day. The total times that males allocated to the two behaviors were positively correlated, i.e. those males that spent longer searching for females, also feed for longer periods. Males, however, tended to allocate more time to the female-searching in the morning than in the afternoon, while time allocated to feeding throughout the day. Older males spent more time searching for females in the morning. The body weight of male butterflies also changed as they aged. The results are discussed in terms of both proximal and ultimate aspects of female-search.

Mate preference in males of the cabbage butterfly, Pieris rapae crucivora, changes seasonally with the change in female UV color

Abstract We initially investigated whether females of the cabbage butterfly, Pieris rapae crucivora, exhibit a seasonal change in ultraviolet wing color, which is a key stimulus for mate recognition by conspecific males, and whether and how a seasonal change affects the mating behavior of the males. We found that female UV wing color changes seasonally, the color being more pronounced in summer than in spring or autumn. We also demonstrated that male mate preference changes seasonally, concomitantly with the change in female UV color. Specifically, males appearing in summer exhibit a mating preference for summer-form females over spring- or autumn-form females, while those appearing in spring or autumn exhibit no seasonal preference, thereby facilitating more effective mate location. Our results suggest that this field of study will require more strictly controlled experimental investigation in which the seasonal change in UV color is considered when UV-influenced mating behaviors such as mate choice are investigated.

Egg activation and timing of sperm acceptance by an egg in honeybees (Apis mellifera L.)

Summary. Mechanical stresses by a narrow glass capillary were applied to unfertilized eggs of honeybees to determine whether the removal of meiotic blocks of the eggs could be caused by simple mechanical stimuli. The treated eggs developed into the anaphase of the first meiotic division at 15 min after treatment, whereas the untreated eggs remained arrested at the metaphase of the first meiotic division. The results of histological examination of the common oviduct showed that its inner widths were sufficiently narrow to cause the distortion of eggs passing through it. The distorted eggs could be fertilized and develop into diploid embryos if they were exposed to the semen immediately (within 30 sec) after egg distortion. However, this would not happen if the distorted eggs were exposed to semen later (30 min). The eggs exposed to the semen but not given mechanical stimuli could initiate the embryonic development with diploid chromosomes. The interval between mechanical distortion and sperm acceptance by eggs in vitro is compatible with that of natural oviposition of fertilized eggs by honeybee queens. These results suggest that egg activation by mechanical stresses in the common oviduct is valid for the natural oviposition in honeybees.