Valley elderberry longhorn beetle
Encyclopedia
The valley elderberry longhorn beetle, Desmocerus californicus dimorphus, is a subspecies
of longhorn beetle
native to the riparian forests of the Central Valley of California
from Redding
to Bakersfield
. It is listed as a Federally threatened species, although it is likely to be removed from the endangered species list .
) with antennae
about as long as their bodies. Females are slightly more robust than males, measuring about 1.9–2.5 cm (¾–1 in), with somewhat shorter antennae. Adult males have red-orange elytra
(wing covers) with four elongate spots. The red-orange fades to yellow on some museum specimens. Adult females have dark colored elytra.
There are four stages in the animal's life: egg
, larva
, pupa
and adult
. The species is nearly always found on or close to its host plant, elderberry
(Sambucus species). Females lay their eggs on the bark. Larvae hatch and burrow into the stems. The larval stage may last 2 years, after which the larvae enter the pupal stage and transform into adults. Adults are active from March to June, feeding and mating. Adults have been observed feeding on the leafy foliage of the elderberry plant.
It appears that in order to serve as habitat, the shrubs must have stems that are 2.5 cm (1 in) or greater in diameter at ground level. Use of the plants by the animal is rarely apparent. Frequently, the only exterior evidence of the shrub's use by the beetle is an exit hole created by the larva just before the pupal stage. Field work along the Cosumnes River
and in the Folsom Lake
area suggests that larval galleries can be found in elderberry stems with no evidence of exit holes. The larvae either succumb before constructing an exit hole or are not far enough along in the developmental process to construct an exit hole.
's Central Valley riparian forests has occurred during the last 150 years due to agricultural and urban development. According to some estimates, riparian forest in the Central Valley have declined by as much as 89% during that time. The valley elderberry longhorn beetle, though wide-ranging, is in long-term decline due to human activities that have resulted in widespread alteration and fragmentation
of riparian habitats, and to a lesser extent, upland habitats, which support the beetle.
The primary threats to survival of the beetle include:
Insecticide
and herbicide
use in agricultural areas and along road right-of-ways may be factors limiting the beetle's distribution. The age and quality of individual elderberry shrubs/trees and stands as a food plant for beetle may also be a factor in its limited distribution.
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of longhorn beetle
Longhorn beetle
The longhorn beetles are a cosmopolitan family of beetles, typically characterized by extremely long antennae, which are often as long as or longer than the beetle's body...
native to the riparian forests of the Central Valley of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
from Redding
Redding, California
Redding is a city in far-Northern California. It is the county seat of Shasta County, California, USA. With a population of 89,861, according to the 2010 Census...
to Bakersfield
Bakersfield, California
Bakersfield is a city near the southern end of the San Joaquin Valley in Kern County, California. It is roughly equidistant between Fresno and Los Angeles, to the north and south respectively....
. It is listed as a Federally threatened species, although it is likely to be removed from the endangered species list .
Description
Valley elderberry longhorn beetles (Desmocerus californicus dimorphus) are stout-bodied. Males range in length from about 1.25–2.5 cm (½–1 in; measured from the front of the head to the end of the abdomenAbdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
) with antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
about as long as their bodies. Females are slightly more robust than males, measuring about 1.9–2.5 cm (¾–1 in), with somewhat shorter antennae. Adult males have red-orange elytra
Elytron
An elytron is a modified, hardened forewing of certain insect orders, notably beetles and a few of the true bugs ; in most true bugs, the forewings are instead called hemelytra, as only the basal half is thickened while the apex is membranous...
(wing covers) with four elongate spots. The red-orange fades to yellow on some museum specimens. Adult females have dark colored elytra.
There are four stages in the animal's life: egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
, larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
, pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
and adult
Imago
In biology, the imago is the last stage of development of an insect, after the last ecdysis of an incomplete metamorphosis, or after emergence from the pupa where the metamorphosis is complete...
. The species is nearly always found on or close to its host plant, elderberry
Elderberry
Sambucus is a genus of between 5 and 30 species of shrubs or small trees in the moschatel family, Adoxaceae. It was formerly placed in the honeysuckle family, Caprifoliaceae, but was reclassified due to genetic evidence...
(Sambucus species). Females lay their eggs on the bark. Larvae hatch and burrow into the stems. The larval stage may last 2 years, after which the larvae enter the pupal stage and transform into adults. Adults are active from March to June, feeding and mating. Adults have been observed feeding on the leafy foliage of the elderberry plant.
It appears that in order to serve as habitat, the shrubs must have stems that are 2.5 cm (1 in) or greater in diameter at ground level. Use of the plants by the animal is rarely apparent. Frequently, the only exterior evidence of the shrub's use by the beetle is an exit hole created by the larva just before the pupal stage. Field work along the Cosumnes River
Cosumnes River
The Cosumnes River is a river in northern California in the United States. It rises on the western slope of the Sierra Nevada and flows approximately into the Central Valley, emptying into the Mokelumne River in the Sacramento-San Joaquin Delta.-Name:...
and in the Folsom Lake
Folsom Lake
Folsom Lake is a reservoir in Northern California about northeast of Sacramento in Placer, El Dorado, and Sacramento Counties. The lake is formed by Folsom Dam, constructed in 1955 to control the American River. The dam and lake are part of the Folsom Project, which also includes the Nimbus...
area suggests that larval galleries can be found in elderberry stems with no evidence of exit holes. The larvae either succumb before constructing an exit hole or are not far enough along in the developmental process to construct an exit hole.
Critical habitat
- Sacramento Zone — An area in the city of Sacramento enclosed on the north by the Route 160 Freeway, on the west and southwest by the Western Pacific railroad tracks, and on the east by Commerce Circle and its extension southward to the railroad tracks.
- American River Parkway Zone — An area of the American River Parkway on the south bank of the American River, bounded on the north by latitude 38 37'30" N, and on the South and east by Ambassador Drive and its extension north to latitude 38 37'30" N, Goethe Park, and that portion of the American River Parkway northeast of Goethe Park, west of the Jedediah Smith Memorial Bicycle Trail, and north to a line extended eastward from Palm Drive.
Special considerations
Extensive destruction of CaliforniaCalifornia
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
's Central Valley riparian forests has occurred during the last 150 years due to agricultural and urban development. According to some estimates, riparian forest in the Central Valley have declined by as much as 89% during that time. The valley elderberry longhorn beetle, though wide-ranging, is in long-term decline due to human activities that have resulted in widespread alteration and fragmentation
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
of riparian habitats, and to a lesser extent, upland habitats, which support the beetle.
The primary threats to survival of the beetle include:
- loss and alteration of habitat by agricultural conversion
- inappropriate grazing
- levee construction, stream and river channelization, removal of riparian vegetation and rip-rapping of shoreline
- nonnative animals such as the Argentine ant, which may eat the early phases of the beetle
- recreational, industrial and urban development.
Insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...
and herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...
use in agricultural areas and along road right-of-ways may be factors limiting the beetle's distribution. The age and quality of individual elderberry shrubs/trees and stands as a food plant for beetle may also be a factor in its limited distribution.
Further reading
- Barr, C. 1991. The Distribution, Habitat, and Status of the Valley Elderberry Longhorn Beetle Desmocerus californicus dimorphus. Sacramento, CA.
- Eng, L. L., 1984. Rare, threatened and endangered invertebrates in California riparian systems. In: California riparian systems Ecology, conservation, and productive management, ed. R. E. Warner and K. M. Hendrix. Berkeley: University of California Press.
- Thelander, C. ed. 1994. Life on the edge: a guide to California's endangered natural resources. BioSystem Books. Santa Cruz, CA. p 414-415.
- U.C. Berkeley, Essig Museum of Entomology. California's Endangered Insects.
- U.S. Fish & Wildlife Service. 1980. Listing the Valley elderberry longhorn beetle as a threatened species with critical habitat. (PDF) Washington, DC.
- U.S. Fish & Wildlife Service. 1984. Valley elderberry longhorn beetle recovery plan. Portland, Oregon.
- U.S. Fish and Wildlife Service. 1996. Valley elderberry longhorn beetle consultation with the U.S. Army Corps of Engineers. Sacramento, California. Appendix: Conservation Guidelines for the Valley Elderberry Longhorn Beetle, Updated July 9, 1999.