Tropical Orbweaver

Appearance

Females vary from 12-24 mm in length and from nearly white to nearly black in color. Typically in Florida, females have a mostly reddish-brown cephalothorax and legs, with darker femora (Figure 1). The dorsum of the abdomen is gray to brown. The venter of the abdomen has a black triangular mark pointing posteriorly; this mark is surrounded by gray laterally and by white anteriorly and posteriorly (Levi 1970). In life, the anterior lateral corners of the abdomen are sometimes bright yellow; unfortunately, this color fades to gray after lengthy preservation in alcohol. The integument is covered with white setae, especially on the carapace and legs.

Males vary from 9 to 13 mm in length. They are similar to females in color. The abdomen is much smaller than that of the female and is usually dark gray. The legs are usually banded. The carapace has a deep longitudinal thoracic groove (Levi 1970). When the male is actively moving about, its palpi can be seen as large anterior structures which appear to flare out to the sides.

Color and pattern variation is extensive in Florida juvenile specimens and in adults in more tropical areas. The abdominal dorsum may have a pattern of white spots (Figure 2), may have a narrow central white stripe (Figure 3), the entire dorsum may be brilliant green in life (Figure 4), and two humps may be present posteriorly. The latter character, when present, further enhances the resemblance of juveniles to the genus Eustala, with which they are frequently confused (Levi 1970).

Behavior

Eriophora ravilla inhabits open woodland, ranging from live oak in scrub areas to "hammock" (Levi 1970). I have found it most frequently in mesophytic situations. Where the understory is fairly dense, Eriophora ravilla will make webs in the tree canopy. I have taken a female from the top of a television antenna, about 16 m above ground.

Orb webs of adult female Eriophora ravilla have a widely spaced spiral and may be over 1 m across (see photograph in Levi 1977). The bridge thread supporting the web may be 6 m long (M. Stowe in Levi 1977). The web is constructed after dark and the orb is taken down before dawn. The bridge and frame threads are probably left in place (Levi 1977). The web probably catches many moths and other night flying insects; these spiders may be particularly beneficial along woodland borders of field agroecosystems and within orchards. It is known to occur in citrus groves in Florida (Mansour et al. 1982). All stages apparently occur throughout the year, but little else is known of its life cycle.