An aedeagus is a reproductive organ of male insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s through which they secrete sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...

 from the testes during copulation with a female insect. Very loosely, it can be thought of as the insect equivealent of a mammal's penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

, though the matter is actually quite more complex.

The aedeagus is part of the male's abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...

, which is the hindmost of the three major body sections of an insect. The pair of testes of the insect are connected to the aedeagus through the genital duct
Duct (anatomy)
In anatomy and physiology, a duct is a circumscribed channel leading from an exocrine gland or organ.-Types of ducts:Examples include:-Duct system:...

s. The aedeagus is part of the male insect's phallus, a complex and often species-specific arrangement of more or less sclerotized flaps and hooks which also includes in some species the valvae
In biology, a clasper is a male anatomical structure found some groups of animals, used in mating.Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve as intromittent organs used to channel semen into the female's cloaca during mating...

 (clasper), which are paired organs which help the male hold on to the female during copulation. During copulation, the aedeagus connects with the ovipore
An ovipore is a pore-like sexual organ of a female insect that gets inseminated by the spermatophores ejected by the aedeagus of a male insect during copulation. The spermatophores that pass through the ovipore are stored in most insect species in another organ called spermatheca....

 of a female.

The sperm of arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s is not passed to the female as liquid with free-swimming spermatozoa, but contains capsules called spermatophore
A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...

s in which the actual spermatozoa are enclosed. In addition to the spermatophores, in some species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 the aedeagus also discharges a spermatophylax
A spermatophylax is a gelatinous bolus which some male insects eject during copulation with females through their aedeagi together with spermatophores, and which functions as a nutritive addition for the female....

, a ball of nutritious
Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with a healthy diet....

 secretions to aid the female in producing offspring.

In males of most species of Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...

, the aedeagus has a sheath which is supported by an organ called the juxta
For the open source bibliographical software, see Juxta .The juxta is an organ in the males of most Lepidoptera that supports the aedeagus, the organ used for reproduction in insects. The juxta is located between the two valvae....

, which is located between the aforementioned valvae.
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