The speckled wood (Pararge aegeria) is a butterfly found in and on the borders of woodland areas throughout much of the Palearctic realm. Furthermore, the species Pararge aegeria comprises four subspecies: Pararge aegeria aegeria, Pararge aegeria tircis,
Description
The average wingspan of both males and females is , although males tend to be slightly smaller than females. Furthermore, males possess a row of grayish-brown scent scales on their forewings that is absent in the females. P. a. tircis and P. a. aegeria gradually intergrade into each other.
Food sources
Larval food plants include a variety of grass species such as Agropyron (Lebanon), Brachypodium (Palaearctic), Brachypodium sylvaticum (British Isles), Bromus (Malta), Cynodon dactylon (Spain), Dactylis glomerata (British Isles, Europe), Elymus repens (Lebanon), Elytrigia repens (Spain), Holcus lanatus (British Isles), Hordeum (Malta), Melica nutans (Finland), Melica uniflora (Europe), Oryzopsis miliacea (Spain), Poa annua (Lebanon), Poa nemoralis (Czechia/Slovakia), Poa trivialis (Czechia/Slovakia), but the preferred species of grass is the couch grass (Elytrigia repens). The adult is nectar feeding. A high growth rate can also negatively affect larval survivorship. Those with high growth rates will also have high weight-loss rates if food becomes scarce. They are less likely to survive if food becomes available once again.
Mating behavior
In the speckled wood butterfly females are monandrous; they typically only mate once within their lifetime. On the other hand, males are polygynous and typically mate multiple times. In order to locate females, males employ one of two strategies: territorial defense and patrolling. Then, the female must make a choice between mating with a patrolling male or a territorial male. By mating with a territorial male, a female can be sure that she has chosen a high quality male, as the ability to defend a territory reflects the genetic quality of a male. Therefore, by choosing a territorial male, the female is being more picky about which male she chooses to mate with.
The choice is most likely dependent on the search costs associated with finding a mate. When actively searching for a male, a female must spend her precious time and energy, which results in search costs, especially when she has a limited life span. As search costs increase, female choosiness for a mate decreases. For example, if a female's life span is shorter, she has a higher cost associated with searching for the ideal mate. Therefore, she is likely to mate within a day of her emergence as an adult, and will most likely mate with a patrolling male, as they are easier to find. However, if a female lifespan is longer, then the search costs associated with finding a mate are lower. The female is then more likely to actively search for a territorial male. Since the search costs vary depending on environmental conditions, strategies vary from population to population. The pattern of flight during this encounter depends on the vegetation. In an open understory, the pair fly straight upwards. In a dense understory, this flight pattern is not possible, so the pair spiral upwards.
In most of these interactions, the conflict is relatively short, and the resident male wins. The intruder most likely backs down as a serious confrontation could be costly, and there is an abundance of equally desirable sunspots. However, if both males believe they are the "resident" male, the conflict escalates.
Both genders of the speckled wood butterfly exhibit asymmetrical wings; however, only males show directional asymmetry (likely to be caused by genetic factors). In addition to body mass, the number of eggs laid by a female may also be related to the time spent searching for an oviposition site. The number of eggs laid is inversely proportional to egg size. However, egg size was not found to have any influence on egg or larval survival, larval development time, or pupal weight under experimental conditions. One explanation may be that there is a tradeoff between the number of eggs laid and the time spent searching for the optimal oviposition site. A female would produce more eggs in an optimal environment, so she can produce more offspring and increase her reproductive fitness.
Paternal investment
During copulation in butterfly species, the male deposits a spermatophore in the female consisting of sperm and a secretion high in proteins and lipids. The female uses the nutrients in the spermatophore in egg production. In a polyandrous mating system, where sperm competition is present, it is beneficial for males to deposit a large spermatophore in order to fertilize the largest amount of eggs possible and possibly prevent the female from mating again.
Since most females in the speckled wood butterfly behave monandrously, there is decreased sperm competition, and the male's spermatophore is much smaller relative to other species.