User:Jeremy.winkler/sandbox

Pemphigus spyrothecae is a social insect that has always been considered as having altruistic behaviors. The aphids form galls and act as colony defenders, sometimes sacrificing their own lives to do so. It has been seen that colony defense is expected in habitats that are difficult to obtain but that can hold a large number of individuals. (Fortress repair in the social aphid species Pemphigus spyrothecae). These gall locations are so crucial because plants have a short window in which a gall can be produced (Fortress repair in the social aphid species Pemphigus spyrothecae). Because of this it is important for there to be a defense system that allows organisms to retain their galls. The need for defense arises when the gall is opened up to allow winged aphid migrants to leave and to release any waste (Fortress repair in the social aphid species Pemphigus spyrothecae). The process of repairing the holes, in P. spyrothecase, can take up to 10 days; during this time, the gall is susceptible to predators entering the gall. (A review on self-destructive defense behaviors in social insects)

In a P. spyrothecae gall, at least one quarter of the population will be cloned first-instar soldiers that are tasked with defending the gall (Clonal mixing in the soldier-producing aphid Pemphigus spyrothecae (Hemiptera: Aphididae)). These soldiers have different morphological states than other members of the species. Firstly these first-instar soldiers tend to be more aggressive than others. Secondly, the first instars have thick hind legs and a stylet, which is used to attack invaders. (Clonal mixing in the soldier-producing aphid Pemphigus spyrothecae (Hemiptera: Aphididae)) and (The Ecology of Altruism in a Clonal Insect). It is typically believed that only the first-instar soldiers will be involved in the defense of the gall (Clonal mixing in the soldier-producing aphid Pemphigus spyrothecae (Hemiptera: Aphididae))).

The effectiveness and method of gall defense was outlines by W.A. Foster. He selected galls and placed them in laboratory conditions so that the predators and number of aphids could be controlled. Anthocoris minki was identified as the primary predator. It was shown that the first instars alone were responsible for the defense; they were successful in preventing predators from entering and killing them if they did. The sterile-soldiers tend to live closer to the gall opening while the sexually active aphids tend to live farthest from the opening (Clonal mixing in the soldier-producing aphid Pemphigus spyrothecae (Hemiptera: Aphididae)). It was also found that some of the soldiers died in this act (Experimental Evidence for Effective and Altruistic Colony Defence against Natural Predators by Soldiers of the Gall-Forming Aphid Pemphigus spyrothecae (Hemiptera: Pemphigidae)). When a ladybird larvae (Adalia bipunatate) was introduced to the gall, the soldiers would walk onto the predator and insert their stylets into the predators cuticles and would occasionally pierce the cuticle with their hind legs. This experiment was also performed with only non-soldiers and in these scenarios the predator was not killed. This indicates that only the soldiers play a role in gall defense. While attacking a predator, haemolymph oozed out and caused the aphids to stick to predator. It was found that with larger predators, more aphids were stuck after the predator was defeated. The predator survival rate is related to the number of soldiers present; with only 50 soldiers 50% of predators died, with 100 soldiers 90% of predators died. ((Experimental Evidence for Effective and Altruistic Colony Defence against Natural Predators by Soldiers of the Gall-Forming Aphid Pemphigus spyrothecae (Hemiptera: Pemphigidae))

The primary explanation for this apparent altruism is explained through kinship; the average degree of mixing in P. spyrothecae was 0.68% which indicated a high relatedness between members of the gall. This now becomes clear that this is a selfish act in order to preserve their genes. This soldier trait has evolved 4 times independently in Aphids; this shows the important and benefits of this trait. It is also interesting to note that while the soldier aphids do protect against predators they seem to not have any tendencies of defense against immigrants of the same species, even though they are not clones. ((Experimental Evidence for Effective and Altruistic Colony Defence against Natural Predators by Soldiers of the Gall-Forming Aphid Pemphigus spyrothecae (Hemiptera: Pemphigidae))