Cheiracanthium inclusum

Current valid name

Cheiracanthium inclusum (Hentz) (family Miturgidae)

Recognition and diagnostic features

Generic-looking wandering spider, most often dull yellow in color although abdomen can vary depending upon the color of recently eaten prey. Often with darkened tarsi. Identification may be limited to exclusion of other species. Mature males have very unique spur on the palp. In C. inclusum, there is only one large projection of the tibial apophysis whereas in the closely related species C. mildei, there are two small projections. In female C. inclusum, the genital opening is a non-descript oval.

Related or similar species

Cheiracanthium mildei

Spider

Body lengths when mature: male: 4.1 to 7.6 mm, female: 4.8 to 9.2 mm

Immatures resemble miniature adults.

Egg sac

Description: oblate spheroid, 2.5 mm thick, 4 mm in diameter, eggs visible through silk covering, constructed inside a large silk sac with more tightly woven silk in which the female takes residence during incubation, typically in a folded leaf or between vegetation, can make egg sac inside grape bunches

Number of eggs per sac: mean = 38 (range 17 to 86) although one study lists 112 eggs in one sac

Number of egg sacs per female lifetime: mean = 2.05 (range 1 to 5)

Size of egg: 1.028 mm

Time of year eggs are likely to be laid: late March to May, September

Distribution

In California: ubiquitous, most often associated with agroecosystems

Elsewhere: throughout continental United States except northernmost climates

Probably not native to North America

This species probably has been transported and become established outside of its range.

Biology

Nocturnal wandering spider which captures prey mostly by random movement. In the lab, males mature in 112 days and live an additional 43 on average (range 21 - 76). Females mature in 142 days and live an additional 70 on average (range 10 - 176). Females live inside maternity retreat with eggs about 17 days duration. Female must open egg sac in order for spiderlings to emerge.

Status in table grapes

Level of Incidence: very common

Level of Concern in New Zealand: WPNZ (MAY 2010) R, BORIC (DEC 2011) R, MAF-BPRA (2002) nr (coding definition)

Level of Concern in Australia: WPAU (2006) R (coding definition)

Level of Medical importance: minor, bites readily, painful at inception, self-limiting effects

Common name

Agrarian sac spider for species, yellow sac spiders for genus

Taxonomic history

There may appear to be misspellings of the genus name in the literature. The genus was initially described as Cheiracanthium, but later taxonomists felt that this was an incorrect transformation from Greek to Latin and "corrected" the spelling to Chiracanthium, which was used in publications for many years. However, one cannot change an original spelling of a species name unless the name is already assigned to another animal or there was a type-setting error. Hence, Cheiracanthium was reinstated. Also, Cheiracanthium was in the family Clubionidae for decades but was recently transferred to the Miturgidae.

Commonly encountered synonyms

Chiracanthium inclusum

Selected references

Cameron, H. D. 2005. An etymological dictionary of North American spider genus names. pp. 274-330, In: Spiders of North America: an identification manual, D. Ubick, P. Paquin, P. E. Cushing, V. Roth (eds). American Arachnological Society.

Edwards, R. J. 1958. The spider subfamily Clubioninae of the United States, Canada and Alaska (Araneae: Clubionidae). Bull. Mus. Comp. Zool. 118: 366-436 + 23 plates

Peck, W. B., and W. H. Whitcomb. 1970. Studies on the biology of a spider, Chiracanthium inclusum (Hentz). Bull. Univ. Arkansas Agric. Exper. Sta. #753, 76 pp.

Vetter, R. S., G. K. Isbister, S. P. Bush and L. J. Boutin. 2006. Verified bites by Cheiracanthium spiders in the United States and Australia: where is the necrosis? Amer. J. Trop. Med. Hyg. 74: 1043-1048.