silk embioptera social insect entomology

Silk-spinning and Sub-social

The Embioptera

Isn’t it ironic that I should never have researched members of an insect order that I find most fascinating? I am referring to the foot-spinners (or Embioptera as they are scientifically called).

I became interested in them during the time I was working on my PhD at the Australian National University in Canberra in the early 1970s. At that time sixty five species of Embioptera had been described from Australia, but in tropical countries there are many more species. These approximately one centimetre long, darkish and ant-like insects (but without a narrow waist) have a life-long ability to spin silk with glands located on their front legs, hence their vernacular name of “foot-spinners”. Their silk retreats or nests can be found on fence posts, tree stumps and rocky outcrops.

Foot-spinners are clearly gregarious and you may find thousands of individuals in one common nest. However, their social organization has not reached the level of sophistication that characterizes the “states” of the truly social insects like termites, ants, non-solitary wasps and bees. Foot-spinners do not have a caste system or an obvious division of labour and they do not help in the rearing of their siblings. Yet, to some extent they share food and shelter and through a system of inter-connected silk tubes create a communal environment of controlled humidity and temperature.

Only the short-lived males have the ability to fly around, seeking receptive virgins. Copulation achieved, the males soon die and sometimes may serve as food to the otherwise vegetarian females. Usually one or several females live in the midst of their broods. A female guards her eggs and the newly hatched young, but thereafter displays only a minimal amount of maternal care. Being hemi-metabolous insects and thus not requiring a pupal developmental stage, the young foot-spinners look like their parents, but are of course smaller. They grow by moulting and start to extend their parental silk home towards the sides by constructing their own silk tunnels at an early stage. Their food, like that of the adults, consists of plant debris, lichens, and dead matter and their life span is estimated to be about a year.

Because this group of insects has a lifestyle that occupies a position halfway between what the entomologist calls the solitary and the social insects, foot-spinners are given the label “sub-social”. I am a little surprised that not more research has been conducted on this group. Perhaps the super-social human societies could learn a few things from the sub-social foot-spinners – perhaps how to exist peacefully together, to manage the climate, or to make a thin and warm silk stocking and create a cosy home (but definitely not how males are to be treated).

masses swarm migration biology move

For more reading about real communities : click here for “Masses on the move”

© Dr V.B. Meyer-Rochow and, 2016.
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