Exam II: Social Insects (5)

Eusocial Insects (long version) (handout)

-Division of Labor within a caste system. -Caste System Involves sterile workers which assist fertile reproductives. -Cooperation among colony members in rearing young. -Overlap of generations to assure continuance of genetic line.

What is Subsocial behavior? (Handout)

1. Aggregations (non-reproductive; overwintering-roosting of monarch butterflies) 2. Parental care (eggs are laid and larvae are given varying care for) 3. Subsocial Nesting (composed of stinging nests only) 4. Parasitoids (killing and eating their prey, using preys burrows as their own, etc.) 5. Pollen-feeding Insects (bees and some wasps) 6. Communal nesting.

9 categories of Response

1. Alarm 2. Simple attraction 3. Recruitment (to a new food source or nest sites) 4. Grooming (including assistance at molting) 5. Trophallaxis (exchange of oral and anal liquid) 6. Exchange of solid food particles 7. Group effect (increasing or inhibiting a given activity) 8. Recognition (of both nestmates and members of particular castes) 9. Caste determination (either by inhibition or stimulation)

How are aspects of Termite and Eusocial Hymenoptera sociality similar (8 ways)?

1. The castes are similar in number and kind, especially between termites and ants. 2. Trophallaxis occurs and is an important mechanism in social regulation. 3. Chemical trails are used in recruitment as in the ants, and the behavior of trail laying and following is very similar. 4. Inhibitory caste pheremones exist , similar in action to those found in honeybees and ants. 5. Grooming among individuals occurs frequently and functions at least partially in the transmission of pheremones. 6. Nest odor and territoriality generally occur. 7. Nest Structure is of comparable complexity. Regulation of temperature and humidity within the nest operates at about the same level of precision. 8. Cannibalism is widespread in both groups, but not universal.

What are ants' social structure?

All ants are eusocial, polyetheistic, and polymorphic. •Polymorphism occurs between reproductives and workers, but can also occur in worker subcastes. •Alates = winged reproductives - for dispersal. •Queen's role is limited to laying eggs. Workers are never winged. They forage and rear young. •In some species, the larger individuals have defensive roles. •Some workers may serve as storage chambers for nectar (honeypot ants). Caste is determination is trophogenic.

Explain termite social structure.

All termites are eusocial, polymorphic, and polyetheistic. •Termites are hemimetabolous. •Termite colonies are made up of both males and females. -ALL termite colonies contain a primary reproductive pair (queen and king) •Nymphs have functional roles in the colony. Soldiers - usually are larger than the workers and have sclerotized heads and large mandibles. Some have nozzle-like heads that shoot sticky substances. They play specialized defensive roles in thhe colony. •Workers - are unspecialized. Not sclerotized and weakly pigmented. •Castes can change tasks as they age. •A new nest is founded by a pair of winged termites called alates. •First offspring are workers. •Workers are fed by the parents - this introduces the symbiotic microbes to their gut.

What is Kin Selection and how does it work?

Behavior is not adapted for individual survival but rather for survival of the gene pool. •Individuals act to enhance the reproductive survival of their kin, hence their own gene pool. Ex.Female worker bees have 75% genetic relatedness of sisters vs. the 50% relatedness when sexual reproduction occurs.

Define Trophogenic and how does it work?

Caste differentiation is generally trophogenic meaning that an individual insect's caste is determined by the amount (quantity) and type (quality) of food it is given by the worker bees. For example, In honey bees fertilized eggs develop into female larvae. Females that are fed "royal jelly" (sugar and gland products) develop into queens and female larvae that are given "bee bread" (pollen and nectar)develop into worker bees.

Termites:How is caste determined?

Caste of an individual termite develops over time (age polyetheism). The difference between castes are genetic, however genetic expression (phenotype) is modified by hormones, environmental factors, and interactions between colony members.

How is labor divided in such a system?

Division of Labor within a caste system. -Caste System Involves sterile workers which assist fertile reproductives. -Cooperation among colony members in rearing young. -Overlap of generations to assure continuance of genetic line.

What is Juvenile Polymorphism?

Early instar nymphs (aphids) have "horns" and scorpion like arms. They are aggressive and will defend the colony from intruders, and defend food resources.

What happens when a honey bee hive gets too crowded?

When a hive gets too crowded or too large, the founder queen with some workers leave the hive for a new nest site. Scouts communicate the directions to a new site, the group moves to the site and establishes a new hive.

Eusocial Insects (short version) (text)

Having the highest level of social organization:reproductive division of labor, overlapping generations, and cooperative care of young.

Why are honey bees important?

Honey bees are important because of their economic significance. Approximately 90% of commercial crops are fertilized by honey bees. *Additionally, honey and bees wax are commercial cash commodities.

What role do pheromones play?

Pheromones appear to: 1. Modify colony behavior 2. Keep the female workers from reproducing viable eggs. 3. Keep males and females docile. 4. Influence how the larvae are fed, and as a result how many queens are produced. 5. Production of new queens takes places in cells most distant from the queen.

What is Subsocial behavior? (long web definition)

Subsocial behavior is "postovipositional (after egg laying) parental care that promotes survival, growth and development of the offspring" (Tallamy & Wood 1986). Subsocial behavior can take the form of egg or nymphal and larval guarding, the construction of simple or elaborate nests, and provisioning of offspring with food collected by the parent.

How do aspects of sociality differ in Termites than in Eusocial Hymenoptera (7ways)?

1. Caste determination in the lower termites is based primarily on pheremones; in some of the higher termites it involves sex. but the other factors remain unidentified. Caste determination in Eusocial hymenoptera (E.H)is based primarily on nutrition, although pheremones play role in some cases. 2, In termites, the worker castes consists of both females and males. While in E.H. the worker castes consist of females only. 3. In termites, larvae and nymphs contribute to colony labor, at least in later instars. While in E.H. the immature stages (larvae and pupae) are helpless and almost never contribute to colony labor. 4. In termites there are no dominance hierarchies among individuals in the same colonies, while in E.H. dominance hierarchies are commonplace, but not universal. 5. In Termites social parasitism among species is almost wholly absent, while in E.H social parasitism among species is common and widespread. 6.Exchange of liquid anal food occurs universally in lower termites and trophic eggs are unknown. In E.H. anal trophallaxis is rare , but trophic eggs are exchanged in many species of bees and ants. 7. In termites the primary reproductive male ("king") stays with queen after the nuptial flights, helps her construct the first nest, and fertilizes her intermittently as the colony develops (fertilization does not occur in the nuptial flight). While in E.H, the male dies shortly after fertilizing the queen during the nuptial flight without helping with nest construction.

What do each of the castes do?

1. The fertile queen is larger than the other castes. she has a greatly enlarged abdomen, her stinging apparatus is small and retractable allowing repeatable assaults on aggressive workers (does not lose stinger). 2. The workers are small (easy movement within the colony) and have developed morphological adaptations which allow them to bring food back to the colony. Their hind legs consist of a series of "combs" which collect pollen and a pocke or corbicula into which the pollen is raked and stored into until it is emptied into a storage chamber at the colony. 3. Drones , or fertile males, are short lived and contribute very little to colonly. They die immediately after mating, having left their genitalia inside the female. Those that are unable to reproduce are driven out of the colony by females and often die shortly after since they don't know how to forage. 4. Caste differentiation is generally trophogenic meaning that an individual insect's caste is determined by the amount (quantity) and type (quality) of food it is given by the worker bees. 5. Fertilized eggs develop into female larvae. Female that are fed "royal jelly" (sugar and gland products) develop into queens and female larvae that are given "bee bread" (pollen and nectar)develop into worker bees.

In what ways are wasps eusocial?

1. Wasps have a caste system: Colony consists of one queen who devotes her self to reproduction and laying only a few fertile eggs (males). She is attended by female worker wasps. Workers distribute food, clean cells, dispose of litter and dead larvae, provide ventilation, defend the nest, forage for water and prey items, construct nest cells and repair the nest. 2. Worker wasps have underdeveloped ovaries and very small genitalia which means they are sterile.

What are the three qualities that have led to the success of social insects?

1.Separation of tasks, as provided by the caste system, means that one group protects the nest while others are out foraging. The nest is not vulnerable to attack during foraging events. 2. Large numbers of individuals can act together to overcome difficulties or larger predators. 3. Specialization of function allows some homeostatic regulation of the colony's climate and population numbers.

Major Orders of Eusocial Insects

Isoptera (termites) and Hymenoptera (bees, ants, and wasps).

Wasps:Explain the various divisions of labor and the structure of the nests.

In many wasp species, worker duties change as the wasp ages (Polyethism). •Newly emerged workers tend to nest duties. •Middle aged workers forage for prey. •Older workers defend the nest. The nests consists of root support, main nest pillar, an entrance to nest tunnel, nest envelope, worker and queen cells, and a nest entrance. In initial stage it consists of root support, a buttress, spindle and a comb attached to the root support.

Describe the social structure of a honeybee colony.

The colony consist of a fertile queen (Gyne), sterile female workers, and fertile males (drones).

What is a corbicula?

The corbicula or pollen basket (consisting of a depression fringed by stiff setae) is located on the outer surface of a worker honey bee's hind leg. The pollen is raked and stored into the corbicula until it is emptied into a storage chamber at the colony.

Describe the division of labor in a Eusocial group.

The division of labor within the colony, witha caste system comprised of reproductive group or queen (gyne), who is aided by sterile workers, and maybe defended by a group of soldiers (ants and termites only). Queens may be unable to feed themselves and may be tended to and fed by workers. The workers will also feed the larval brood as well. The queen also exudes a pheromone, which is distributed by the workers throughout the colony, keeping a "chemically induced peace."