humpbacked orbweaver

(Eustala anastera)

Conservation Status
humpbacked orbweaver
Photo by Alfredo Colon
  IUCN Red List

not listed


NNR - Unranked


not listed


Humpbacked orbweaver is a small typical orbweaver. It occurs in the United States from Maine to North Dakota south to Florida and California, in southern Quebec and Ontario Canada, and in Central America. It is very common in the east, less common in Minnesota. It is found in open woodlands and woodland edges on trees and shrubs. During the day it rests on a dead twig or branch, where its color and markings camouflage it well, making it difficult to see.

The female is 316 to (5.4 to 10 mm) in length and has a to ¾ (10 to 20 mm) legspan. The male is slightly smaller, to (3.9 to 9.5 mm) in length.

The front part of the body (cephalothorax) is much smaller than the abdomen. The upper side (carapace) is mostly brown but dark on the sides. The thoracic region has a deep longitudinal furrow in the middle and is covered with long white hairs and with shorter downy hairs.

There are eight eyes arranged in two parallel rows of four eyes each. The eyes are not on raised projections (tubercles). The rear row is slightly curved forward, the front row is straight or slightly curved backward. All of the eyes are small, but the median eyes are larger than the lateral eyes, and the posterior median eyes (PME) are slightly smaller than the anterior median eyes (AME). On each side the lateral eyes are widely separated from the middle (median) eyes and are almost touching each other. The median ocular area (MOA), the area defined by the middle four eyes, is longer than wide and narrower in front than behind. There is a often a dark band on the face between the anterior lateral eyes (ALE) and the AME, and this band is sometimes continuous across the face. There is sometimes also a dark band between the PME.

The abdomen is large, longer than wide, and triangular when viewed from above, widest in front and pointed at the rear. When viewed from the side it appears squarely cut off (truncate) with a distinct hump at the end above the spinnerets. This is the feature that gives the species the first part of its common name. Some females have two or three humps in a line. There are no humps in the shoulder area (humeral tubercles). The color and markings on the upper side is variable but follows one of three basic patterns. It is most often gray or light brown with a dark, scalloped, triangular mark (folium) stretching from the front to the rear. The folium is sometimes faint. Some individuals have a bold dark stripe in the middle of the abdomen with the folium faint or missing. Some individuals have a white abdomen and a black folium with either three large black spots on the front margin or a continuous irregular black band on the front margin. The underside of the abdomen has a large black patch surrounding a white spot.

The legs are spiny and mostly gray or light brown with irregular dark bands. The first pair of legs is the longest, the third pair is the shortest. On the male, the first segment (coxa) on the front pair of legs has a hook-like spur on the underside. This spur fits into a groove on the upper side of the third segment (femur) on the second pair of legs.




Female Body Length: 316 to (5.4 to 10 mm)

Male Body Length: to (3.9 to 9.5 mm)

Legspan: to ¾ (10 to 20 mm)




A loose web with few threads is often constructed on a dead branch away from leaves or on a tree trunk. It is called an “orb”, which gives this family of spiders its common name. The orb is (19 to 30 cm) in diameter and has 18 to 21 radii and 58 to 64 sticky (viscid) threads. Webs of juveniles are smaller and have more threads. The web hangs more or less vertically and is somewhat asymmetrical, largest on the lower half. It is an open web with a medium-sized hole in the center. There is no retreat.


Similar Species










Adults are active at night and rest on a dead branch during the day. The web is constructed in the evening after dark and is torn down in the morning, usually before daylight. When resting it usually keeps its legs slightly spread.


Life Cycle


The eggs are hung on a radius of the web.

Spiderlings in the final development stage (instar) overwinter.






Distribution Map



24, 29, 30, 82.





  Class Arachnida (arachnids)  


Araneae (spiders)  


Araneomorphae (typical spiders)  
  Infraorder Entelegynae (entelegyne spiders)  
  Superfamily Araneoidea (araneoid spiders)  


Araneidae (orbweavers)  


Araneinae (typical orbweavers)  







Common Names


humpbacked orbweaver












The hard, upper (dorsal), shell-like covering (exoskeleton) of the body or at least the thorax of many arthropods and of turtles and tortoises. On crustaceans, it covers the cephalothorax. On spiders, the top of the cephalothorax made from a series of fused sclerites.



The front part of a spider’s body, composed of the head region and the thoracic area fused together. Eyes, legs, and antennae are attached to this part.



On insects and arachnids, the third, largest, most robust segment of the leg, coming immediately before the tibia. On humans, the thigh bone.



On some spiders, the leaf-shaped marking on the upper side of the abdomen.



The developmental stage of arthropods between each molt; in insects, the developmental stage of the larvae or nymph.



The fourth segment of an insect leg, after the femur and before the tarsus (foot). The fifth segment of a spider leg or palp.



On plants and animals: a small, rounded, raised projection on the surface. On insects and spiders: a low, small, usually rounded, knob-like projection. On slugs: raised areas of skin between grooves covering the body.





Visitor Photos

Share your photo of this arachnid.

  This button not working for you?
Simply email us at
Attach one or more photos and, if you like, a caption.

Greg Watson

    humpbacked orbweaver      

Alfredo Colon

    humpbacked orbweaver   humpbacked orbweaver  








Visitor Videos

Share your video of this arachnid.

  This button not working for you?
Simply email us at
Attach a video, a YouTube link, or a cloud storage link.


Other Videos



Visitor Sightings

Report a sighting of this arachnid.

  This button not working for you?
Simply email us at
Be sure to include a location.
  Greg Watson

Location: Reno Quarry Trail, Reno North Recreational Area

humpbacked orbweaver  
  Alfredo Colon

Location: Woodbury, MN

humpbacked orbweaver  
  Alfredo Colon

Location: Woodbury, MN

humpbacked orbweaver  






Created: 1/11/2022

Last Updated:

About Us | Privacy Policy | Contact Us | © All rights reserved.