Objects Worthy of Notice: Insects both Large and Small

When Thomas Jefferson directed Lewis and Clark to observe “objects worthy of notice,” he went on to specify “the animals of the country generally, & especially those not known in the U.S.” This instruction included insects, and the Corps of Discovery did not disappoint. Jefferson also directed Lewis to pay close attention to the seasons, and the ““times of appearance of particular birds, reptiles or insects.” As such, insects are mentioned frequently throughout his journals and those of the other men. Here are a handful of insects seen by members of the Expedition during their time in the western United States.

Crane Fly

It’s understandable how Clark would mistake the humble crane fly for a mosquito. The two insects appear similar at a glance, save for one glaring difference: size. Adult crane flies have bodies around 1 inch in length and a wingspan up to 3 inches. Mosquitoes in this region, by comparison, rarely exceed 0.4 inches. Crane flies also lack the taste for blood, instead feeding on plants and decaying organic matter. Crane flies are abundant in humid, temperate environments. They occupy vegetation near rivers, lakes, and streams. They can be found worldwide with over 15,500 species. Crane flies are beneficial decomposers. They benefit their ecosystems by consuming decaying plant matter, which leads to improved soil quality and microbial activity. Crane flies are also an important food source for birds, amphibians, and other animals.


In October of 1805, the Expedition crossed into flea country. Having avoided the little pests up until this point, they became an unpleasant new obstacle. Fleas infested Fort Clatsop, resulting in an itchy, uncomfortable winter for the Corps of Discovery. Fortunately, a cold snap in January 1806 provided them with some much needed relief. Two weeks of frigid temperatures killed off a large portion of the flea population, and there were no more recorded complaints about fleas for the rest of the journey. Fleas are small, flightless insects. They are considered external parasites, laying their eggs and feeding on living mammals and birds. There are approximately 2,500 species of flea and they can be found worldwide. Though they lack wings, they have powerful rear legs that allow them to jump fifty times their own height. Fleas can live their entire lifecycle on one host, laying eggs in hair or fur. Larvae then feed on dead skin and organic debris on the host until they are mature enough to consume the host’s blood. Fleas can transmit a variety of diseases and were responsible for deadly plagues like the Justinianic plague and the Black Death.


Ticks are Parasitiformes, parasitic arachnids that live on the blood of living animals. Contrary to popular belief, ticks don’t jump onto their hosts. Instead, they cling to plants in humid climates and forests, waiting for a host to brush by. Once a tick is on a host, it burrows its head into the skin to feed. Ticks can take anywhere from minutes to hours to latch on to a host. Their saliva has anti-inflammatory properties that make bites painless and hard to find. They feed on the host for several days before dropping off. The tick’s notoriety comes from its potential as a disease vector, usually Lyme disease. Lyme disease is a bacterial infection characterized by intense fever, fatigue, rashes, and headaches. Without proper treatment, the infection can spread to the nervous system, heart, and joints. Other diseases carried by ticks include Colorado tick fever and Rocky Mountain spotted fever. Clark may have had his own encounter with disease-carrying ticks in June of 1805. He was stricken with fever, chills, and muscle pain that incapacitated him for days. Given the time of year, location, and description of his symptoms, he could have contracted Colorado tick fever. However, even if Clark knew he was bitten by a tick, he would not have connected it to his illness. The link between the wood tick and Colorado tick fever would not be made for another hundred years.


Though mosquitoes were dormant for the winter during the Corps’ stay at Fort Clatsop, the biting insects were a constant nuisance during warmer parts of the trip. Most journal entries complaining of mosquito bites are from late spring of 1806 onward. Mosquitos are small flies that feed on blood. The name means “little fly” in Spanish, combining the word mosca, “fly,” with the diminutive suffix, -ito. There are approximately 7,600 species of mosquito worldwide. Mosquitoes tend to live in moist locations and are most active during warmer seasons. Scientists have observed the lunar cycle affecting the activity levels of mosquitos. They are more active at night and can more easily find prey with the light of a full moon. When mosquitoes bite, they transfer a small amount of saliva that can cause an itchy rash. Like other biting insects, mosquitos are frequent disease vectors in some parts of the world. They carry parasitic diseases such as the West Nile virus, yellow fever, and the Zika virus. Through transmitting disease, the mosquito causes more deaths each year than any other animal. Because mosquitos rely on stagnant water to lay their eggs, you can reduce the mosquito population in your area by eliminating still water in buckets, drains, and pools.

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