Transverse Lady Beetle

(Coccinella transversoguttata)

Status: Endangered (ESA 2018), Special Concern (COSEWIC 2016)

Table of Contents:

Species Identification
Diet
Habitat and Range
Biology and Behaviour
Similar Species
Threats/Reasons for Being at Risk
Conservation and Recovery Strategies
How You Can Help

Species Identification:

The Transverse Lady Beetle is a small beetle of about 5-8 mm long, but they are slightly larger than most other Lady Beetles. Adults have orange or red wings with a black band near their head and 4 long black spots. The black band can be used to distinguish the Transverse Lady Beetle from other Lady Beetles. Their head is black with two white spots on either side.

Diet:

Like other Lady Beetles, the Transverse Lady Beetle preys mainly on aphids, as well as other small soft-bodied insects. They will also feed on other nuisance insects and their eggs such as spider mites, alfalfa weevils, leafhoppers, and scale insects. Transverse Lady Beetles will capture and consume prey on the leaves of plants, using their wings to fly from plant to plant.

Map taken from Government of Canada: https://wildlife-species.canada.ca/species-risk-registry/virtual_sara/files/cosewic/sr_Transverse%20Lady%20Beetle_2016_e.pdf

Habitat and Range:

The Transverse Lady Beetle can be found throughout almost all of Canada and the United States. They span coast to coast of the United States, almost down to the Mexican border. In Canada, they also span coast to coast from Newfoundland to Vancouver, and then up to northern Yukon, Northwest Territories, and Alaska. In Ontario, there has not been a confirmed sighting of the Transverse Lady Beetle since 1990, so this species may be close to being Extirpated.

The Transverse Lady Beetle is considered a habitat generalist, which means it can live in a variety of different habitats. These habitats include agricultural areas, urban settings, coniferous and deciduous forests, and grasslands and meadows. They will move across different habitats throughout the year in order to take advantage of prey availability.

Biology and Behaviour:

Very little is actually known about the Transverse Lady Beetle’s life cycle and reproduction. However, they are suspected to have similar cycles as other Lady Beetle species. The Transverse Lady Beetle has 4 forms- egg, larvae, pupae, and adult. They are suspected to have an average life cycle of 20-60 days. They can have 1-2 generations per year depending on conditions. Adults from the spring generation will lay the second generation in the fall, and those adults will overwinter until spring where they lay the next first year generation. The female lays about 20-30 eggs in clusters on various plant species that have aphids to use as a food source. The Transverse Lady Beetle can lay an average of 267 eggs over her short lifetime. She may also lay unfertilized eggs next to fertilized ones, which can be used as a food source for the newly hatched larvae. The transition from egg to adult generally takes about 20 days, 3 days in egg form, 13 in larvae, and 5 in pupae. The adult female gives off chemical trails to lure males during mating season, and both sexes will mate with multiple partners. In the fall, adult Transverse Lady Beetles will find warm and dry places like rock crevices or under foliage to overwinter.

Transverse Lady Beetles use their brightly coloured bodies as a warning to predators, which are mainly birds, frogs, wasps, dragonflies, and ants. While it has not been thoroughly researched, Transverse Lady Beetles- like other Lady Beetle species, are thought to be able to excrete toxins when threatened.

Similar Species:

Transverse Lady Beetles are similar in colour and size to most other Lady Beetle species, but they have a long black bar across both wings near their head that can distinguish them from other species.

Threats/ Reasons for being at Risk:

1. Invasive species: Invasive species generally pose significant threats to similar native species, and the Transverse Lady Beetle is no exception. In fact, in just North America, 179 non-native Lady Beetle species have been introduced, as they are an important predator for pest insects in agriculture. The Seven-spotted Lady Beetle and the Multi-coloured Asian Lady Beetle are two introduced species that are currently outcompeting, predating, or spreading pathogens to the Transverse Lady Beetle.

2. Competition and predation: As mentioned in the above section, the Seven-spotted Lady Beetle and the Multi-coloured Asian Lady Beetle are two of the main species that are outcompeting the Transverse Lady Beetle for resources like habitat and food. Both of these species are able to thrive in a wider variety of conditions which has allowed them to grow in strength and numbers while the Transverse Lady Beetle continues to suffer. The Seven-spotted Lady Beetle has also been known to prey on the Transverse Lady Beetle. Adding another predator to the extensive list of predation threats for this species has further decimated their numbers and chances at survival.

3. Parasites and pathogens: Transverse Lady Beetles also have a high risk of parasites, fungi and disease, many of which were brought in by invasive species. Many of these parasites and pathogens are also able to attack the Transverse Lady Beetle while they are overwintering and are at their most vulnerable. Common parasites include the Braconid Wasp, Mites, and various fungal pathogens.

4. Pollution: While most Lady Beetle species are more tolerant of pesticides than their prey, they are still at risk of mortality from pesticides, especially when there is direct contact, residual buildup, or inhalation and ingestion. Pesticides that are ingested by prey are ingested by the Transverse Lady Beetle, and can cause a buildup of toxins in their body. With the ever increasing need for food and monoculture, pesticides are being used more frequently and more heavily in an attempt to combat pest species like aphids that can heavily impact crops.

Conservation and recovery strategies:

Since the Transverse Lady Beetle is only listed as Special Concern in Canada, there are no direct protections for this species. However, the Transverse Lady Beetle is protected in Ontario since they are listed as Endangered. While Endangered species and their general habitats are protected Provincially, no direct conservation or recovery strategies are in place for the Transverse Lady Beetle. The Transverse Lady Beetle has been found in both protected areas like provincial parks, but also private land in urban and agricultural environments, which make them difficult to protect. Tackling the main threats to the Transverse Lady Beetle would be the first and most important steps to recovering this species, as well as other insect Species at Risk.

How can you help?

Avoid using harmful pesticides and fertilizers in your garden and on your property. Let Lady Beetle species do their work and protect your garden naturally!
Record any sightings of the Transverse Lady Beetle at The Land Between’s website or iNaturalist.
Do not release any non-native predator insects into the environment.
Keep your property natural and encourage native wild plant species to grow. Your helpful, friendly predator insects will thank you!

Additional Resources:

Government of Ontario’s Transverse Lady Beetle page
COSEWIC 2016 Assessment and Status Report on the Transverse Lady Beetle
Transverse Lady Beetle observations from iNaturalist

Sources:

Government of Ontario. 2018. Transverse Lady Beetle. Retrieved from https://www.ontario.ca/page/transverse-lady-beetle

COSEWIC. 2016. COSEWIC assessment and status report on the Transverse Lady Beetle Coccinella transversoguttata in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 57 pp. https://wildlife-species.canada.ca/species-risk-registry/virtual_sara/files/cosewic/sr_Transverse%20Lady%20Beetle_2016_e.pdf