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The mysterious journey of the diamondback moth: Why can this pest cross continents?
The diamondback moth (Trichoplusia ni) is a medium-sized moth belonging to the family Noctuidae, which is often called larval moths. It is named for its favorite host plants and unique crawling behavior. Its main host plants are cruciferous vegetables such as cabbage, bok choy and cauliflower, which is why it contains "diamond moth" in its name. The larvae are called "folding worms" because they arch their bodies into an arc when they crawl. Although they prefer cruciferous plants, over 160 plant species can serve as hosts for diamondback moth larvae.
Adults of the diamondback moth are migratory moths found in North America and Eurasia, from Florida in the south to British Columbia in the north. Their migratory behavior makes their distribution range very wide.
Although the larvae of the diamondback moth are small vegetable pests, especially affecting cruciferous plants, their destructiveness is not significant. However, their wide distribution and resistance to many pesticides make their management increasingly difficult. Many methods of controlling this pest are also being actively researched.
The reproduction and life cycle of diamondback moth
Mating
When diamondback moths are ready to mate, they display by raising their abdomens and flapping their wings. Males not only spread out their abdominal hairs, but also open their genital clamps and partially extend their sperm sacs. After attracting a potential mate, the two will use their antennae to examine each other's abdomens, and if both agree, mating will occur. Most mating occurs at 2 a.m., but there are also observations between 12 and 4 a.m.
Multiple mating is a reproductive strategy in which an individual has multiple partners during his or her lifetime. For female diamondback moths, the more times they mate, the more eggs they lay, which may explain why males release pheromones to attract females.
Egg laying behavior
After mating, the female will seek out a host plant to lay her eggs. The eggs are generally pale yellow, dome-shaped, and are usually laid singly on the underside of leaves. In a single day, 40 to 50 females can lay 1,000 to 2,000 viable eggs, which hatch after about three days.
Distribution and Migration
The diamondback moth is found in North America and Eurasia, from Florida in the south to British Columbia in the north. As the seasons change, populations of diamondback moths in the United States migrate from Mexico to Canada. They usually overwinter in Mexico or Southern California, where temperatures remain above 16°C (61°F) even in winter.
As temperatures rise in northern regions, diamondback moths will gradually move northward, and will not migrate until the temperature reaches 16°C (61°F).
This migration pattern, which changes with temperature, allows the diamondback moth to cross continents, escape severe cold and find suitable environments for raising its young.
The impact of climate
The migration patterns of diamondback moths are closely related to temperature, which affects their development. At 10°C (50°F), the pupae of the diamondback moth will stop developing, and at temperatures above 35°C (95°F) they may develop physical deformities. Therefore, in areas with stable and suitable temperatures, diamondback moths will choose to continue to reproduce and give birth to offspring.
Host Plant Selection
The diamondback moth is an omnivorous insect that can live and feed on more than 160 host plant species. Its preference for cruciferous vegetables, such as cabbage and cauliflower, is partly because the nutrients in these plants make them easier to survive and grow.
Attractive scent
Diamond moths use their sense of smell to find suitable food resources and host plants. Their sensitivity to plant odors helps increase their chances of survival and reproduction. Mated female moths react faster than unmated female and male moths, indicating their high need to find a host plant.
Although diamondback moths are ubiquitous insects, their survival and reproductive success often depend on climate change and the rich diversity of host plants. This creature can not only adapt to various environments, but also cross continents, bringing more challenges and opportunities. Should we rethink how to deal with the expansion and control of these organisms?
