Invisible Invaders, Invincible Insects

Plate 9 from Historia Insectorum Generalis
Jan Swammerdam, Netherlands, 1669
Print, Book
Biodiversity Heritage Library; Cornell University Library
Swammerdam, Jan. Tertivs Ordo Nympha. 1669. Cornell University Library. In Historia Insectorum Generalis. Apud Jordanum Luchtmans, 1685. Plate 9. Accessed December 4, 2018.

This plate, depicting the life cycle of ants, is the work of scientist and medical doctor Jan Swammerdam. Swammerdam trained as a medical doctor at the University of Leiden in 1661, and most of his published works reference medical science and especially the question of how breathing functions. This plate is from one of his rare forays into naturalist science publication, although it seems to have been his passion. His father pressured him into concentrating on medical science, hoping that Jan would earn a practical living, but his many friends encouraged him to follow his true interests and one of them even published his Biblia naturae after his death in 1680. The only works he published during his lifetime were a single monograph of a mayfly (which he proceeded to write a hymn to God about) and this text, the Historia Insectorum Generalis.

Swammerdam’s interest in ants was atypical of the era, and for the most part they went unnoticed. While Swammerdam was stationed in the Netherlands, his illustration of the ant life cycle illuminates the reason these tiny, easily-killed individual organisms can and have become massive problems throughout history and in the contemporary world. Ants, typically,  have a reproductive cycle in which there are one or more “queens” who hold the sole ability to lay eggs. These eggs are all fertilized during a single mating flight during a specific mating period usually indicated by environmental conditions such as humidity, food availability, and—in some areas—whether the nest has been flooded recently. Ant-keepers often encourage increases in their colony size by introducing more food, which stimulates colony growth along with possible mating nymph production. After this mating flight, the queen lands, finds a suitable area to form a nest, and loses her wings. From this single queen, every ant in the colony will be laid and hatched.

This ability to essentially create a colony of several thousand (or more) ants is what makes ants such a potent environmental agent, especially during a time such as the age of the Columbian Exchange when new stimuli were introduced to new countries. While people like Swammerdam showed rare interest in insects and ants in particular, most individuals during the early modern period failed to notice insects at all. One particularly stunning example of ants going unnoticed, despite massive indications of their role in a disaster, took place in Hispaniola in 1518. The Spanish colonists in Hispaniola brought plantain trees from Africa to populate the plantations on the island and probably to help diversify the crops they could sell aside from sugar. Hiding away on these trees, however, was a plague that only became dangerous when introduced to the ecological system of Hispaniola: mealybugs.

When these mealybugs were introduced to Hispaniola, they were also introduced to an army of new friends: fire ants, or Solenopsis geminata. S. geminata is well-known to “herd” or “farm” mealybugs, even “milking” them for the sweet, calorie-rich waste product they excrete called “honeydew”. This new, massive availability of food led to an explosion of ant population, so much so that colonists had to put the legs of their beds in bowls of water to prevent ants stinging them in their sleep as their floors were carpeted with thousands of ants. The plantations withered, but the colonists did not attribute this to the proper invaders; rather, they blamed the ants. The colonists had no care for the mechanisms of ants or how they really functioned. That was unique to people like Jan Swammerdam, with passions that led us to our current understanding of science and specifically modern entomology.