Femoral pores are a part of a holocrine

Holocrine

Holocrine is a term used to classify the mode of secretion in exocrine glands in the study of histology. Holocrine secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the...

 secretory gland found on the inside of the thighs of certain lizard

Lizard

Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

s and amphisbaenians which releases pheromone

Pheromone

A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...

s to attract mates or mark territory. In certain species only the male has these pores and in other species, both sexes have them, with the males being larger. Femoral pores appear as a series of pits or holes within a row of scales on the ventral portion of the animal's thigh.

Femoral pores are present in all genera

Genera

Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

in the families Cordylidae

Cordylidae

Cordylidae is a family of small to medium sized lizards that occur in southern and eastern Africa. They are commonly known as "Girdled", Spinytail lizards or Girdle-tail lizards. Girdled lizards are diurnal and insectivorous...

, Crotaphytidae

Crotaphytidae

The family Crotaphytidae, or collared lizards, are desert-dwelling reptiles native to the southwest USA and northern Mexico. They are very fast-moving animals, with long limbs and tails, and are carnivorous, feeding mainly on insects....

, Hoplocercidae

Hoplocercidae

Family Hoplocercidae, or the hoplocercids, are a family of lizards native to the tropical forests of Central and South America. There are ten described species in three genera...

, Iguanidae

Iguanidae

Iguanidae is a family of lizards, composed of iguanas and related species.-Classification of Iguanidae:Two different classification schemes have been used to define the structure of this family. These are the "traditional" classification and the classification presented by Frost et al. .Frost et...

, Phrynosomatidae

Phrynosomatidae

Phrynosomatidae is a diverse family of lizards, found from Panama to the extreme south of Canada. Many members of the group are adapted to life in hot, sandy deserts, although the spiny lizards prefer rocky deserts or even relatively moist forest edges, and the short-horned lizard lives in prairie...

, and Xantusiidae. They are absent in all genera in the Anguidae

Anguidae

The Anguidae is a large and diverse family of lizards native to the northern hemisphere. The group includes the slowworms, glass lizards, and alligator lizards, among others. Anguidae is divided into three subfamilies and contains 94 species in eight genera. Their closest living relatives are the...

, Chamaeleonidae, Dibamidae

Dibamidae

Dibamidae is a family of legless lizards found in tropical forests. Relatively little is known about the dibamid lizards, which are native to Mexico, SE Asia, Indonesia, the Philippine Islands and western New Guinea....

, Helodermatidae, Scincidae, Xenosauridae

Xenosauridae

The Xenosauridae is a family of lizards native to Central America and China. Also known as knob-scaled lizards, they have rounded, bumpy scales and osteoderms. Most species prefer moist or semi-aquatic habitats, although they are widespread within their native regions, with some even inhabiting...

, and Varanidae

Varanidae

Varanidae is a group of lizards of the superfamily Varanoidea. The family is a group of carnivorous lizards which includes the largest living lizard, the Komodo dragon, and the crocodile monitor. Varanidae contains the living genus Varanus and a number of extinct taxa...

families. They are present in other lizards and amphisbaenians quite variably, some geckoes,Phelsuma

Phelsuma

The genus Phelsuma consists of several lizards in the gecko family, commonly referred to as Day Geckos.-Description:In contrast to most other gecko species, day geckos are active mainly during the day. Other diurnal geckos are members of the genus Lygodactylus and the genus Gonatodes...

, for example have these pores, others in the same family do not.
In the desert iguana

Desert iguana

The desert iguana is one of the most common lizards of the Sonoran and Mojave deserts of the southwestern United States and northwestern Mexico...

 (Dipsosaurus dorsalis), the waxy lipid

Lipid

Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

s released from the femoral pores absorb ultraviolet

Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 (UV) wavelengths making them visible to species which can detect UV light. According to tests performed on the Green iguana

Green Iguana

The Green Iguana or Common Iguana is a large, arboreal herbivorous species of lizard of the genus Iguana native to Central and South America...

, the variation in the chemicals released by the femoral pores can lead to determine age, sex, and individual identity of the animal in question. Male leopard gecko

Leopard gecko

The leopard gecko is a nocturnal ground-dwelling lizard naturally found in the deserts of southern Central Asia, and throughout Pakistan, to the northwestern parts of India. Unlike most geckos, leopard geckos possess movable eyelids...

s (Eublepharis macularius), actually taste the secretions by flicking their tongues, if a male determines the other gecko in question is a male, the two will fight.

In certain species such as geckoes, the females lack femoral pores altogether. In most families of lizards that have femoral pores, notably the iguanids, both sexes have femoral pores, but the males tend to be much larger than females of the same size and age. In these instances they are used as a marker for sexual dimorphism

Sexual dimorphism

Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

.