Crossopriza lyoni is a widespread species of cellar spiders that prefer to live in or around human structures. They are commonly known as tailed cellar spiders, tailed daddy longlegs spiders, and sometimes box spiders. They all possess extremely long fragile legs that can reach up to long and a body length of that ranges from . Their abdomens are distinctly squarish when viewed from the side and their carapace is more or less circular when viewed from above. They also possess two kinds of sound-producing organs and have six eyes.
The original range of C. lyoni is unknown. They have been introduced into other parts of the world accidentally and are now pantropical in distribution. They are a regulated species in some countries and are often regarded as pests due to the large amounts of unsightly webs they construct inside human homes. Some people, however, regard them as beneficial, as they are efficient predators of mosquitoes and other arthropods. They are harmless to humans.
Taxonomy and nomenclature
Crossopriza lyoni are classified under the genus Crossopriza and the subfamily Holocneminae. They belong to the cellar spider family (Pholcidae). They are commonly referred to as tailed daddy longlegs spiders, tailed cellar spiders, or (more rarely) box spiders. C. lyoni and other cellar spiders are also often confused with two other invertebrates - the harvestmen (order Opiliones) and the crane flies (family Tipulidae) - both of which are also known as 'daddy longlegs'. However, they are not closely related to cellar spiders — the latter is a fly; and the former, while also an arachnid, is not a spider at all.
The species was first formally described in 1867 by the British naturalist John Blackwall from a collection of spiders from Meerut, Agra, and Delhi. They came from Francis Lyon, a captain of the Royal Artillery of the British Empire stationed in India. They were sent to his sister who presented them to Blackwall at the suggestion of a mutual friend. Blackwall named the spider after Captain Lyon and expressed a hope that others may follow Lyon's example in collecting specimens from foreign countries for the benefit of science. He classified the species under the genus Pholcus. In 1892, the French arachnologist Eugène Simon erected the genus Crossopriza and subsequently reclassified Pholcus lyoni to Crossopriza lyoni.
Blackwall also described a curious case of hermaphroditism in one adult specimen, in which the left side was male and the right side was female.
Description
C. lyoni are sexually dimorphic. Females of C. lyoni are about in length. Males are slightly smaller, at about in length, and have prominent pedipalps. Both sexes possess extremely long fragile legs. Males have slightly longer legs than females. The first pair of legs in larger male individuals can reach up to in length. The legs are gray to amber in color and covered with numerous small longitudinal brown spots. The 'knee joints' are brown, and the ends of the femur and tibiae are girdled with white. Males also possess a series of 20 to 25 spines (macrosetae) on their femur. Their leg formula is I, II, IV, III - the front pair of legs being the longest and the third pair being the shortest.
The cephalothorax is wider than it is long, greyish-white to pale amber in color. The carapace is subcircular. In the middle of the upper surface is a deep depression (called the thoracic fovea) and a darker longitudinal band of color. C. lyoni, like most other cellar spiders, has eight eyes. They are pearly-white in color and located at the tip of the cephalothorax in two lines.
The abdomen (the opisthosoma) is gray with white lateral stripes and various dark and light patches on the sides and the upper surface. An irregular darker stripe runs lengthwise at the bottom surface. The abdomen is angular and somewhat box-shaped, with a small conical hump on the upper back.
They also possess two types of stridulatory organs. The first type is located at the posterior tips of their cephalothorax (the prosoma) in the form of two triangular protrusions. The spiders rub these structures with a matching pair of sclerotized plates at the anterior portion of the abdomen, producing sound. These structures are more prominent in females. They also possess stridulatory files (in the form of a series of small ridges) on their chelicerae which are rubbed against the pedipalps to produce sound. The second type is more prominent in males.