The lose-to-win strategy of the weak: intraspecific parasitism via egg abduction in a termite

Predation by larger conspecifics poses a major threat to small juveniles in many animal species. However, in social insects, raids perpetrated by large colonies may provide smaller colonies with opportunities for parasitization. Herein, in the termite Reticulitermes speratus , we demonstrate that small incipient colonies parasitize large mature colonies through egg abduction when attacked by raiding conspecifics. We observed that the eggs of incipient colonies were brought into raiding colonies while their parents were killed during the attack. In this species, unmated females found new colonies with female–female (FF) cooperation, in addition to the typical monogamous colony foundation. Interestingly, the abducted eggs of FF pairs developed into nymphs (reproductive caste) in the raiding colonies, whereas the eggs of male–female (MF) pairs developed into workers (non-reproductive caste). Parthenogenetic eggs are known to be developmentally predisposed to becoming female reproductives owing to genomic imprinting in termites. This study demonstrates that the plundering of small colonies by larger conspecific colonies not only results in the extinction of the weaker colonies, but also serves as a strategy that incipient colonies use to obtain the reproductive position in large colonies by stealth. The results elucidate the diversity and complexity of inter-colonial interactions in social insects.

Queens of the inquiline social parasite Acromyrmex insinuator can join nest-founding queens of its host, the leaf-cutting ant Acromyrmex echinatior

Queens of the inquiline social parasite Acromyrmex insinuator are known to infiltrate mature colonies of Acromyrmex echinatior and to exploit the host’s perennial workforce by producing predominantly reproductive individuals while suppressing host reproduction. Here we report three cases of an A. insinuator queen having joined an incipient colony of A. echinatior that contained only the founding host-queen and her small symbiotic fungus garden. We conjectured that 1:1 host-inquiline co-founding—a phenomenon that has only rarely been reported in ants—may imply that the presence of an A. insinuator queen may incur benefits to the host by increasing survival of its incipient colonies. We observed that the parasite queens neither foraged nor defended the nest against intruders. However, the parasite queens interacted with the host and fungus in a way that could be consistent with grooming and/or with contributing eggs. These observations may help explain why A. insinuator queens have maintained metapleural glands, even though they are smaller than those of host queens, and why A. insinuator has lost the large foraging worker caste but not the small worker caste.

Altered Mobility and Accumulation of Inefficient Workers in Juvenile Hybrid Termite Colonies

Hybridization of two different species is an important mechanism to have gene flows between species. Recently, mating of two economically important invasive species of subterranean termites (Coptotermes formosanus and Coptotermes gestroi) have been observed in the field and hybrids colonies have been established in the laboratory. It was previously reported that incipient colonies (~1 year old) of hybrid Coptotermes species contained more termites than colonies of parental species, showing hybrid vigor. In this study, colony vigor and individual termite vigor were investigated in juvenile colonies (~2 year old), using colony growth parameters and the movement activity of individual termites as proxies for the evaluation of hybrid vigor beyond the initial colony foundation. After 2 years from colony foundations, hybrid colonies showed no more hybrid vigor. In addition, movement activity of termites in hybrid colonies was significantly slower than in termites from conspecific colonies. It is suggested that a reduction in the molting rates of individuals in hybrid colonies may have a negative impact on their physiology and their movement activity. These possible changes in physiology may affect the movement of individuals, and accumulation of these inefficient termites in hybrid colonies may contribute to the loss of hybrid vigor at 2 years of age in hybrid colonies.

Effect of diet on incipient colony success for two long-tongued bumblebee species in the laboratory

Bumblebees (Bombus spp.) are ecologically and economically important pollinating insects and nutritional stress is one of the most significant factors causing their decline. However, our knowledge of the nutritional requirements of bumblebees is largely limited to just a small number of species that can be easily reared in the laboratory, so there is an important need to understand the nutritional requirements of a greater range of bumblebee species. In particular, the long-tongued, pocket maker species that have been intractable to laboratory rearing, yet are often of greatest conservation concern. Here, we compare the development and success of incipient colonies in two species of pocket maker bumblebees (B. pascuorum and B. hortorum) when fed either a less diverse or more diverse pollen diet. Our results show that both diets were sufficiently good for queens of both species to rear workers, but they performed significantly better for some variables on the less diverse diet. Our findings support previous work that suggests that a less diverse diet can be as good as a highly diverse mix in some respects. We also observed significant differences between species, demonstrating why we must not rely only on one or two model species to understand the effects of nutritional stress on bumblebee communities.

A Reproductives Excluder for Subterranean Termites in Laboratory Experiments

As a social insect, termites have different castes and division of labor in a colony. Investigating the social behavior of subterranean termites is a challenge due to the cryptic nature and large colony size. Planar arenas are commonly used to study these termites under laboratory conditions, and have provided several advantages. However, there is no means to designate areas such as a royal chamber or central nest from foraging sites because reproductives can move freely across arenas. In this study, we examined the minimum passing size of different castes of Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), in order to develop a reproductive excluder and correlated minimum passing size with head widths and heights. We found that workers and soldiers of C. formosanus were able to pass through a gap greater than or equal to 0.7 mm. Our results showed that there are significant differences in the head width and height based on castes and head height was more critical than head width to determine passing size. We further confirmed feasibilities of the reproductive excluders using incipient colonies of C. formosanus. Confining reproductives using the excluder in laboratory experiments will provide more chances to study the royal chamber and central nest independently of foraging sites.

Fused Colonies of the Formosan Subterranean Termite (Blattodea: Rhinotermitidae) for Laboratory Experiments

Laboratory studies of Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae) often employ the use of field-collected foraging populations of individuals as defined colonies. The biological relevance of this practice is often called into question, because these colonies lack a full composition of reproductive castes and brood, which may have physiological and behavioral consequences. Rearing intact laboratory colonies can be done; however, it is time-consuming and labor-intensive. The artificial fusion of field-collected foraging populations with a young, laboratory-reared incipient colony may provide whole, intact colonies for laboratory research. The current study measures survivorship of fused colonies using laboratory-reared complete incipient colonies ranging in age from 0 to 5 mo, fused with 100 workers and 10 soldiers from field-collected populations of different colonial origin. Results indicate that 60% of colony fusion was successful when the incipient colony introduced is 5 mo of age. This method of colony fusion will provide researchers with intact colonies using minimal resources.