California's Butterflies - Quino Checkerspot

California’s Butterflies

Quino Checkerspot

The quino checkerspot used to be one of the most abundant butterflies found in southern California. Now this species is one of the rarest and is very near extinction. The reasons for its rapid disappearance are complex, but the main cause is simply the loss of habitat to housing and commercial development. The quino checkerspot likes open exposed habitat with little vegetation (see picture below). These areas are also favored by developers. It is estimated that over 95% of the habitat for this species has been lost.

The remaining habitat for this checkerspot is being threatened by the improper use of public lands, such as off road traffic. The quino checkerspot’s larval food plant (Plantago) grows larger and has deeper roots when it is on the dirt paths created by off road vehicles. A female quino checkerspot will actively seek out these larger food plants to lay her eggs (oviposition). The eggs and larvae living on the food plant are later trampled by off road traffic, causing the death of the quino checkerspot larvae. Roads have probably played a role as well since these butterflies like to fly low over open areas, leading to them being killed by fast-moving cars.

At Right: An adult quino checkerspot butterfly (Euphydryas editha quino).

Life History

The quino checkerspot butterfly (Euphydryas editha quino) belongs to a group of butterflies called the Nymphalids or “true brushfoots”. They are called checkerspots because of the black, orange, yellow and white checkerspot pattern on their wings. These butterflies fly in early spring during years of adequate rainfall. The females lay tiny yellow eggs in large clusters of around a hundred or more on their food plant. Each female in the lab on average lays about 500 eggs. Females prefer to oviposit upon leaves that extend out over open soils. The larvae that hatch 10 to 14 days later spin silken shelters that act as protection from predators and parasites. These larvae are called prediapause larvae, meaning they have not yet entered diapause (a form of hibernation). After a few instars, the larvae enter diapause and wait for the following winter rains when their food plants start growing again. At this time the larvae break diapause and the cycle continues. These larvae that start feeding after winter rains are called postdiapause larvae.

At Left: Quino checkerspot habitat near Lake Skinner, CA.

Below, #1: Quino checkerspot eggs on a leaf of Penstemon.

Below, #2: Quino checkerspot first instar larvae forming a silken shelter.

Below, #3: Quino checkerspot larvae.

Below, #4: A quino checkerspot chrysalis.

Diapause

Diapause is somewhat like hibernation, since insects go through this quiescent stage with reduced-to-no measurable metabolism. Unlike hibernation, which mammals use to go through cold winters, insects can enter diapause during any time of year, even during the hottest time of year. It is an adaptation that allows a butterfly to become active or inactive depending on the availability of its food source. Each butterfly has developed adaptations that allow it to respond to the environmental stimuli that affect the availability of its food plants. As an example, the quino checkerspot enters an obligate diapause in spring when its annual food plant becomes dried out. Its diapause is later broken as a response to increased rainfall during fall and winter which causes the annual food plants to grow again.

A larva that has entered diapause will undergo morphological changes. To enter diapause the larva becomes smaller, reducing the size of its head capsule while the branches of its scoli become longer and denser. These denser scoli probably protect the larva in a variety of ways throughout diapause. The larvae keep these morphological changes throughout diapause. After feeding, the larvae are believed to make decisions based on food plant quality on whether to continue diapausing or break diapause. If they continue to feed and exit diapause, they are likely interpreting their food plant as being a high enough quality to grow at least into the next instar. In some cases it is believed that a proportion of larvae will automatically return to diapause as a form of bet-hedging just in case weather conditions suddenly turn bad and cause the food plants to die and dry up before butterflies can oviposit and/or prediapause can complete development enough to enter diapause.

The quino checkerspot exhibits a complex diapause biology. This is due to adaptations allowing some larvae to enter and re-enter diapause over a multiple-year period. In case of a prolonged drought that lasts for multiple years, some larvae need to be capable of returning to diapause for the species to continue to survive. It is believed that some respond to the quality of food plants differently because of genetic variability in the population. Some larvae will return to diapause even if the quality of the food plant is relatively good, while others will not re-enter diapause even when conditions are poor. There is probably some variability in the population from one end of the extreme (never returning to diapause) to the other (staying in diapause for multiple years).

The number of larvae that remain in diapause, re-enter diapause or mature to adults is variable both within a population and between separate populations. Also, it probably is different from year to year. After winter rains the annual food plants for the quino checkerspot begin to grow with the quality and number of plants reflecting the quantity of rainfall, humidity and temperature conditions between rainfalls. After these rains some number of larvae that were in diapause will begin feeding. The number of larvae that exit diapause probably depends on the amount of rainfall. It would make sense that increased precipitation would cause more larvae to become active. Some of these larvae that feed will return to diapause and find a new diapause site, while others will continue to feed and shed out of diapause into another instar.

Diapause Sites

In 2006, one thousand diapausing larvae were released in the fenced enclosure at the facility (see picture below). These larvae were observed as they moved about and fed upon the food plants. The purpose of this study was to determine if larvae will return to diapause and where they will go to enter diapause. The enclosure was watered daily so those larvae that returned to diapause were likely ones that would return to diapause even under high quality conditions. The fenced enclosure is surrounded by large areas of blacktop so it is unlikely that any of them were able to escape and survive outside of the enclosure.

Although only 49 larvae were found that had returned to diapause, nearly 80 percent of these larvae had found diapause sites in California Buckwheat. Under these same conditions around 40 larvae pupated and 32 formed adults. The remaining larvae probably died due to predators (such as spiders and predatory insects) and parasites. There were hundreds of spiders in the leaf litter within the fenced enclosure. The main diapause site chosen by quino checkerspot larvae was at the main branch point of the California Buckwheat where most of the branches met.

Mating

Hundreds of quino checkerspots have been mated at the Murrieta Facility. In order to mate the males need to be aged 3 days. During this period the males are fed daily a 1:3 buckwheat honey-water mixture and maintained in cages. Females, after being fed the same mixture, are kept in the refrigerator. Once the males have been aged they are taken out into the fenced enclosure and are warmed by sunlight. When they start chasing each other, a female from a different parental lineage is taken from the refrigerator and is brought out to the cage of males.

The female is held carefully between the fingers and the tip of her abdomen is rubbed against the antennae of a chosen male. If the male is interested he twists his abdomen and begins wing fanning. At this the female is put down beside the male and the male is allowed to mate with the female. Initially after the coupling the male faces in the same direction as the female (see picture #1, below). When he has become comfortable with the mating he turns around and faces away from the female (#2). At this point the pair is removed from the cage and put into a labeled container (#3). If the coupling is greater than one-half hour and less than 12 hours the mating is generally successful. Once the female has been mated she is then set up on Penstemon branches within an oviposition container (#4).

Below: The fenced enclosure at the Murrieta facility.

Larval Food Plants

Lab Colonies

Quino checkerspot larvae feed on several closely related plants. Previously these plants belonged to the Scrophulariaceae and Plantaginaceae families, but because of relationships shown by DNA studies these families have been changed. Some of the Scrophulariaceae have been found to be more closely related to the Plantaginaceae family than they are to other members of the Scrophulariaceae. Presumably because of these evolutionary relationships these plants share the same or similar biochemicals that act as ovipositional and feeding stimulants. These ovipositional stimulants are the biochemicals that females use to oviposit (lay eggs).

There are three main food plants for quino checkerspot larvae. Erect Plantain (Plantago erecta) is used at low elevations (up to about 3,000 feet elevation). White Snapdragon (Antirrhinum coulterianum) and Chinese houses (Collinsia concolor) are used at higher elevations (up to 5,000 feet elevation). The extent that White Snapdragons and Chinese houses are used at low elevations is not known at this time, but it seems likely that some of the extirpated Santa Monica Mountains populations used Chinese houses or White Snapdragon rather than Erect Plantain. These populations are believed to be extirpated at this time. There are areas in Temecula where both the White Snapdragon and the Erect Plantain are used as food plants. In areas south of Anza, CA quino checkerspot larvae have been observed feeding on Chinese houses, White Snapdragon and to a lesser extent Patagonia Plantain (Plantago patagonica).

Other minor food plants include Owl's clover (Castilleja exserta) and Birdsbeak (Cordylanthus rigidus). These lesser used food plants may play a role in the survival of some populations. For instance, Birdsbeak remains green late into the season and sometimes blooms even into the fall. This plant provides food for prediapause larvae into diapause, when Plantago may not. But the problem with Birdsbeak is that it grows very slowly during the winter so it does not support late instar (postdiapause) larval development. This can be extremely useful since Plantago can die and dry out even before quino checkerspot eggs even hatch. There are some locations in western San Diego County where the soils are shallow so even though the Plantago erecta will support late instar (postdiapause) development they will not support prediapause larval development. In these cases the Birdsbeak will serve as prediapause larval food plants.

Adult Nectar Sources

Quino checkerspots have been found nectaring on many plants in the field. Male quino checkerspots have even been found nectaring on non-native mustards. But the most favored nectar plants are in the family Asteraceae, Boraginaceae, and Hydrophyliaceae. Female quino checkerspots are often found on Chaenactis glabriuscula and Ericameria linearifolia in the Asteraceae family, on Cryptantha species in the Boraginaceae family, and Eriodictyon species and Phacelia species in the Hydrophyliaceae family. Many other plants are also nectared upon.

The lab colonies are being maintained for lab experiments and for the future potential of release back into their native environment. With the recent fires in southern California there is some concern that many populations of the quino checkerspot may have been extirpated. With increased fire frequency it is possible that the quino checkerspot could become extinct.

We have populations from four different regions in southern California. These four regions were chosen to reflect the greatest differentiation within the species. We have a fairly large population of quino checkerspot from the Lake Skinner area. This area is to represent the populations from low elevations of western Riverside County. There are about 10,000 larvae at present being maintained in diapause for this area. Butterflies have been maintained in captivity by mating between different parental lines, crossing with males from Lake Skinner, and by collecting some females from Lake Skinner. These populations are only being mated with butterflies from the same area.

Another area from which we a have considerable number of larvae in diapause is an area from Marron Valley in San Diego County along the Mexican border. This population is to represent the low elevations of western San Diego County. Interestingly this population appears to be the easiest to maintain in captivity. It does well in the tanks used for rearing and appears to be easier to mate in captivity compared to the other populations.

A third population being maintained is from south of Anza in Riverside County. This population was chosen since it is found at higher elevations and is largely adapted to Antirrhinum coulterianum and uses Plantago patagonica during years of poor rainfall. It is found above 4,000 feet elevation. Perhaps due to the high elevation adaptations this population is more difficult to maintain in captivity. It may require colder conditions for rearing than the other populations. We have hundreds of larvae of this population in diapause at the lab.

The fourth population is found north of Jacumba along the desert edge in southeastern San Diego County. This population is considered potentially unique since it is found with desert butterflies and is found in a desert habitat. There are very few from this population remaining at the facility (<10). We hope to increase the numbers in this population this coming season. This population came largely from two females collected in 2002.

Captive Breeding

Diapausing larvae are maintained in yogurt containers inside the ‘Diapause Room’ at the Murrieta facility. They are put into this room as soon as the prediapause larvae enter diapause. This behavior is determined by the number of larva creating shelters together, curling up into balls, shedding into a smaller diapause larva form, and ceasing to feeding.

In mid-October soil is put into flats, watered, and Plantago erecta seeds are placed into the top 1/8^th inch of soil. The flats are watered daily at 4:40 PM for about 40 minutes. Three to four weeks later the seedlings will begin growing and several weeks later the plants will be ready for larvae. New flats of Plantago erecta are started once a week, so there is a constant source of food for growing larvae. Quino Checkerspot larvae prefer new young plants over those that are older.

Once Plantago erecta seedlings are started, diapausing quino checkerspot larvae are broken from diapause. These larvae will be from the diapause room and populations from different regions will be started once a month to keep each region separate from one another. For example, only larvae from Lake Skinner will be reared during one month, Anza during the next month, Marron Valley during the third month, and Jacumba during the fourth month. Diapause is broken by collecting the larvae from a yogurt container and placing them inside a plastic container with a wet paper towel and Penstemon gloxinoides branches. The Penstemon is used by the larvae as a food source. The containers are opened twice daily: once when we arrive at the facility in the morning and another time just before we leave.

After about 10 days the larvae will have broken from diapause. This will be determined by the larvae feeding behavior. If there is extensive feeding in the first 7 days the paper towel will be removed and new wet paper towels and Penstemon branches will be added to the plastic container.

After about 10 days the larvae are placed into glass tanks with Plantago erecta flats at the bottom. The Penstemon branches from the plastic containers will be added with the larvae. These branches will be eaten for a short period of time before the larvae quickly change to feeding on the Plantago erecta plants. Each tank contains about 50 to 150 larvae, generally of a single parentage. Each tank also has a light set to a 10 hours light/14 hours dark photoperiod.

These larvae will feed for about three to four weeks upon the Plantago and then start pupating. In some cases when the Plantago quantity or quality is dropping Penstemon branches are added as a food plant. The larvae will often feed upon the Penstemon as well as the Plantago. The larvae then start to pupate on the plants. The pupae are removed and placed into labeled containers inside cages where the adults hatch 10 to 14 days later. The adults will be mated to one another as described in the ‘Mating’ section. Those larvae that return to diapause will be put back into yogurt containers and returned to the diapause room.

Hilltopping

Male and female butterflies in the wild have to find each other in order to mate. Hilltopping is one method that the different sexes use to find each other. (Another is to patrol and perch along drainages.) When a mate is difficult to find, a female quino checkerspot can find males by searching hilltops. Male quino checkerspots appear to fight each other on hilltops in order to determine which male can use the hilltop to attract females. Presumably the male that gets the best hilltop will be the most successful at mating. Hilltops without trees, rocks, and bushes are favored. Searching open hilltops for male quino checkerspots is one of the best methods for finding this butterfly species.

Below, at left: Quino checkerspot eggs on Collinsia concolor.

Below, center: Quino checkerspot larvae on Collinsia concolor.

Below, at right: Quino checkerspot larvae feeding on Collinsia concolor.

At Left: A Chinese house (Collinsia concolor) growing in a bare spot. This particular Chinese house had quino checkerspot eggs laid upon it.

At Right: A more distant shot of the same location as above. Note that even though there are many Chinese houses in the picture, only the one growing in the bare spot was oviposited upon. Quino checkerspot females seem to prefer to oviposit on food plants that are growing in bare areas of ground.