Numbers of tents of western tent caterpillars over time for six areas in British Columbia Canada and population characteristics for the population on Galiano Island
Data files
Feb 06, 2026 version files 4.46 KB
Abstract
This paper is a historical account of the experiments and observations on the population dynamics of western tent caterpillars, Malacosoma californicum pluviale, beginning in the 1975 through 2025. It contains figures of population trends and characteristics of the populations that vary with population density to show that infection by Mcplnucleopolyhedrovirus (extrinsic factor) and changes in fecundity and early larval survival (tent size) (intrinsic factors) relate to the population change.
Numbers of tents of western tent caterpillars over time for six areas in British Columbia Canada and population characteristics for the population on Galiano Island
Dataset DOI: 10.5061/dryad.sxksn03fz
Myers_Cory_tent_caterpillar_Gulf_Islands_population_data.csv
Description of the data and file structure
The long-term cyclic population dynamics of the Western Tent Caterpillar were studied for 50 years in western British Columbia, Canada. This included monitoring populations in six areas by annually counting observed tents. Characteristics of the populations were determined by collecting egg masses and counting the eggs per egg mass as a measure of fecundity, measuring the length and width of the tents that could be accessed as an estimate of the early larval survival, collecting and rearing family groups of 10 larvae to determine the occurrence of infection from nucleopolyhedral virus and parasitism of larvae, and determining the annual rate of increase based on the population data
Files and variables
File: Myers_Cory_tent_caterpillar_Gulf_Islands_population_data.csv
Description: Contains the annual counts of the number of tents for the six study sites for the years 1975 (or when the counts began) until 2025 and used in Figure 3 and 5 of the paper. 'NA' indicates not available.
File: Myers_Cory_tent_caterpillar_Galiano_population_data.csv
Description: csv file
Variables:
- Year
- Tent size is the length times by the width (cm2),
- Fecundity (number eggs per egg mass),
- % families infected with Mcplnucleopolyhedrovirus,
- % individuals parasitized by wasps and/or flies,
- rate of population increase (loge(nt+1/n)) for the Galiano population and used in analyses in Figure 4 of the paper.
'NA' indicates not available.
Code/software
Microsoft Excel was used for working with the data and Prism was used to make the figures.
Methods - Myers_Cory_tent_caterpillar_Gulf_Islands_population_data.csv
Since 1975, tents were counted each May on the 7 ha Mandarte Island by following a set path around the whole island and scanning for tents on all the vegetation we could see using binoculars. Over the next 10 years additional sites on other islands and locations were identified and defined areas were monitored. On Galiano Island the main site is an approximately one kilometer section of road A second site on Galiano Island is at Montague Harbour where the host trees are primarily domestic apples, Malus domestica, and wild rose. On Saturna Island, the site is a grassy area surrounded by red alder trees. The Westham site is an open field along a slough and a dyke extending westward toward the Strait of Georgia. Crab apple (Malus diversifolia) and alders are the dominant host trees. Alders are also the dominant host trees on Cypress Mountain, where monitoring comprises three sites along the road up the mountain.
Methods - Myers_Cory_tent_caterpillar_Galiano_population_data.csv
In addition to counting the number of WTC tents annually, we monitored changes in fecundity (number of eggs per mass) and early larval survival as indicated by tent size (maximum length x width) when the larvae were in the fourth instar. In 1990, we began monitoring the levels of infection by McplNPV using DNA analysis (Kukan and Myers 1997). Beginning in 1999, NPV infection in all sites was estimated by collecting samples of 10 fourth instar larvae per tent (family) and rearing them on alder leaves in the laboratory until one larva died of viral infection or pupation occurred. The number of parasitoids emerging from the larval samples was also recorded.