Wildlife & National Parks of Thailand

เว็บไซต์ชุมชนสำหรับการแบ่งปันข้อมูล ภาพถ่ายและประสบการณ์เกี่ยวกับสัตว์ป่า ความหลากหลายทางชีวภาพและพื้นที่คุ้มครองในประเทศไทย มาร่วมกันสร้างความตระหนักที่มีต่อโลกอันงดงามรอบตัวของเราด้วยกัน
Wildlife Thailand is a community website for sharing information, photographs and experiences on Thailand's wildlife, bio-diversity and protected areas. Creating awareness of this wonderful world around us.

Nephilengys malabarensis – the Malabar Orb-Weaver, is a member of a rather bizzare group known as Eunuch Spiders. This bulky, medium size spider displays a handsome livery of either yellow and black or red / orange and black. The females are considerably larger than the males with a body length of 15 to 20mm while the males are a mere 5mm. 

Their name derives from the Malabar Coast of India where they were first described but their range extends through the tropics to the Philippines and as far north as Yunnan, China. Nocturnal by nature they retire to a tube like web and emerge either when darkness falls or when an insect becomes entrapped in it’s extended web. 

 As with many species of spider, the males must run the gauntlet of courtship and cannibalism in order to reproduce and continue their kind. The Nephilidae family to which they belong has evolved a rather special technique to overcome the inconvenience of sudden death during the nuptials. The male’s pedipalps (palps) which transfer sperm to the female have evolved to become large and highly specialized structures that can break off during the copulation allowing the male to escape and avoid becoming part of the mating menu. The palps remain in place and continue to pump sperm into the female even when detached and act as an anti-copulation cork making it harder for rivals to successfully pass on their sperm.

 

The female has two openings called epigynum so if only one gets blocked there is still room for a rival. Self castration might seem rather extreme but it may allow the male sufficient time to escape his murderous mate. Minus his palps the eunuch spider will guard the female and research has shown that emasculated males are superior fighters and more aggressive, winning more encounters than their potential, non-castrated rivals. Minus just one palp the male can lose 4% of his body weight while the loss of both palps can mean a 9% reduction. What they lose in body parts and corresponding weight they gain in endurance levels which can increase as much as 30% for a single loss to 80% for a fully castrated spider.

 

Photo - Kaeng Krachan National Park - Thailand

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