Tsuyoshi Takeuchi

Territorial Behavior of a Green Hairstreak Chrysozephyrus smaragdinus (Lepidoptera: Lycaenidae): Site Tenacity and Wars of Attrition

Abstract Males of Chrysozephyrus smaragdinus were active from late morning to late afternoon, during which they showed territorial behavior, perhaps for mating. The territorial male stayed in a particular area and occasionally flew around it, referred to hereafter as the inspection area. When other male intruded into this area, the territorial male rushed to him. Then, they engaged in a circling flight regarded as a “war of attrition”. During this flight, the two males sometimes strayed far away from the territory. After the circling flight, the resident returned to his territory in almost all cases (98%). Despite such intrusions, many residents defended their territory for several successive days. This suggests strongly the “effect of prior residence”. We recorded the circling flights with a high-speed video camera, and confirmed that the male that ceased the circling flight first was the loser. This finding gave some validity to consider circling flight as wars of attrition. In a few cases, the territorial male mated with a female that came to the territory. These once mated males held the territory no longer, suggesting that mating experience should restrict the next mating opportunity in this species.

Wing Colors of Chrysozephyrus Butterflies (Lepidoptera;Lycaenidae): Ultraviolet Reflection by Males

Wing colors of the four species of Chrysozephyrus butterflies were analyzed by a spectrophotometer. As the dorsal wing surface of males showed a strong reflectance when the specimen was tilted, measurements were made by the tilting method. The dorsal wing surface of males which appears green to the human eye reflected UV (315–350 nm) as well as green light (530–550 nm). The reflectance rate of UV to visible green light varied among species with a higher rate for C. hisamatsusanus and C. ataxus, and a lower rate for C. smaragdinus and C. brillantinus. The peak wavelength and the peak height did not shift when the specimen was exposed to direct sunlight at least for 16 hr. Artificial removal of scales by scratching the wing surface decreased reflectance. Blue marks on the forewings of C. brillantinus, C. hisamatsusanus and C. ataxus females reflected UV to visible light of short wavelength, and orange marks on the dorsal surface of the forewing and the ventral surface of the hindwing of C. samaragdinus females showed a higher reflectance at longer wavelengths.

Cost of reproduction in males of a satyrine butterfly Lethe diana

Adult butterflies feed largely on floral nectar and tree sap, both of which consist mainly of carbohydrates and include little nitrogen. They depend on the larval diet for nitrogenous resources. Consequently, there is a trade‐off between the reproductive and somatic nitrogenous investments of adults. Furthermore, male butterflies invest a considerable amount into spermatophores, containing nitrogen, which they give to their sexual partners. One way in which male butterflies could potentially replenish their spermatophores is by flight muscle histolysis, which may reduce locomotor ability and lifespan. In the present study, the effect of mating experience on nitrogen dynamics and the lifespan of males is investigated in the satyrine butterfly Lethe diana (Butler). Mated males do not have less thoracic nitrogen than virgin males, suggesting that mating experiences do not induce spermatophore recovery through flight muscle histolysis. Mated males possess less abdominal nitrogen than virgin males at death, indicating that they cannot recover the lost nitrogenous resource used for a single mating. Lifespan does not differ between mated and virgin males. Thus, reproduction and longevity are not fuelled necessarily by the same shared resource pools. Spermatophore mass increases as males get older. Considering that resources for producing spermatophores are limited, males may adjust the spermatophore mass strategically, depending on their chances of future reproduction.

Mate-Locating Behavior of the Butterfly Lethe diana (Lepidoptera: Satyridae): Do Males Diurnally or Seasonally Change Their Mating Strategy?

The mate-locating behavior of male butterflies has been classified into two major types, territorial and patrolling. Territorial males defend a specific site, whereas patrolling males fly around a wider area without having to defend a site. In this study, I investigated the use of these tactics by males of the satyrine butterfly, Lethe diana. A previous study suggested that the males of L. diana change their mate-locating behavior during the day (they patrol in the morning and defend territories in the afternoon) and that patrolling is the primary mating strategy, whereas defending territories is a supplementary one. In the present study, I found that the daily activity pattern of the males of L. diana was similar to that described in the previous study: males often flew around in the morning and competed for territories in the afternoon. However, contrary to the previous study, all courtships and copulations were performed within male territories during their territorial activity. Closer observations revealed that copulations found in male territories were achieved by the owner of the territory. Males tended to feed in the morning, suggesting that the males flying in the morning searched for food rather than females. I conclude that territory holding is the primary male matelocating tactic in L. diana. I further found that, in summer, males exhibited territorial behavior later than in spring or autumn, which may be a strategy for preventing heat stress.

Body morphologies shape territorial dominance in the satyrine butterfly Lethe diana

Male butterflies compete over mating territories via aerial interactions. It has often been suggested that flight performance, and thus flight-related traits, would play an important role in butterflies’ contest resolution; however, most studies have not demonstrated a clear relationship between these traits and territory ownership in butterflies. Males of the satyrine butterfly Lethe diana compete over territories via linear chases, a behavior that is uncommon among butterflies: rather, contests of most butterfly species consist of circling flights. In the present study, some morphological and physiological traits of L. diana were compared between territory owners and intruders to search for traits correlated with resource holding power (RHP). Territory owners had higher flight-muscle ratio (FMR) and were heavier than intruders, indicating that flight performance plays a key role in their contest resolution. Contest duration was not affected by the owners’ FMR or body mass, and thus I obtained no evidence supporting the hypothesis that contestants assess their relative RHP before making a decision to retreat. I speculate that the fact that these traits had an effect on territorial status in L. diana was a result of the characteristics of the contest behavior of this butterfly. During their contests, males L. diana fly faster in their linear flights than males of most other butterflies, which engage in slower circling flights. Therefore, males of L. diana probably need higher flight performance capabilities in order to win their contests.

A Quantitative Analysis of Geographic Color Variation in Two Geotrupes Dung Beetles

Abstract We conducted a quantitative analysis of geographic color variation in two species of dung beetles: Geotrupes auratus and G. laevistriatus. The reflectance of the dorsal surfaces was measured from 300 to 700 nm using a spectrophotometer. The reflectance curves for both beetles were bimodal; there were two distinct peaks, namely, the α peak, between 400 and 700 nm, and the β peak at around 300 nm. A stepwise discriminant analysis indicated that geographic color variation in Geotrupes beetles was primarily characterized by a shift of the α peak. Using beetles from three locations, we compared the wavelength (nm) of the α peak (λmax(α)) and its reflectance intensity (R(α)) to investigate sex and population differences. Intraspecific geographic variation in coloration was effectively detected by discriminant analysis of spectral reflectance curves. Our results showed that G. auratus and G. laevistriatus had similar coloration within each sampling location. Our study also revealed hidden sex differences in R(α); R(α) of males were significantly higher than those of females in both species. Since the dorsal surface of the beetles shows remarkable color variation, and coloration can be assessed objectively using reflectance spectra, Geotrupes beetles may be good model organisms to investigate geographic color variation.