Sex is the biological trait that determines whether a sexually reproducing organism produces male or female gametes. During sexual reproduction, a male and a female gamete fuse to form a zygote, which develops into an offspring that inherits traits from each parent. By convention, organisms that produce smaller, more mobile gametes are called male, while organisms that produce larger, non-mobile gametes are called female. An organism that produces both types of gamete is hermaphrodite.
A secondary sex characteristic is a physical characteristic of an organism that is related to or derived from its sex, but not directly part of its reproductive system. In humans, these characteristics typically start to appear during puberty. In animals, they can start to appear at sexual maturity. In humans, secondary sex characteristics include enlarged breasts and widened hips of females, facial hair and Adam's apples on males, and pubic hair on both. In non-human animals, secondary sex characteristics include, for example, the manes of male lions, the bright facial and rump coloration of male mandrills, and horns in many goats and antelopes.
Upolu is an island in Samoa, formed by a massive basaltic shield volcano which rises from the seafloor of the western Pacific Ocean. The island is 75 kilometres long and 1,125 square kilometres in area, making it the second largest of the Samoan Islands by area. With approximately 145,000 inhabitants, it is by far the most populous of the Samoan Islands. Upolu is situated to the southeast of Savai'i, the "big island". Apia, the capital, is in the middle of the north coast, and Faleolo International Airport at the western end of the island. The island has not had any historically recorded eruptions, although there is evidence of three lava flows, dating back only to between a few hundred and a few thousand years ago.
Sexual dimorphism is the condition where sexes of the same species exhibit different morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecious species, which consist of most animals and some plants. Differences may include secondary sex characteristics, size, weight, color, markings, or behavioral or cognitive traits. Male-male reproductive competition has evolved a diverse array of sexually dimorphic traits. Aggressive utility traits such as "battle" teeth and blunt heads reinforced as battering rams are used as weapons in aggressive interactions between rivals. Passive displays such as ornamental feathering or song-calling have also evolved mainly through sexual selection. These differences may be subtle or exaggerated and may be subjected to sexual selection and natural selection. The opposite of dimorphism is monomorphism, when both biological sexes are phenotypically indistinguishable from each other.
Solifugae is an order of arachnids known variously as solifuges, sun spiders, camel spiders, and wind scorpions. The order includes more than 1,000 described species in about 147 genera. Despite the common names, they are neither true scorpions nor true spiders. Because of this, it's less ambiguous to call them "solifuges". Most species of solifuge live in dry climates and feed opportunistically on ground-dwelling arthropods and other small animals. The largest species grow to a length of 12–15 cm (5–6 in), including legs. A number of urban legends exaggerate the size and speed of solifuges, and their potential danger to humans, which is negligible.
Spider monkeys are New World monkeys belonging to the genus Ateles, part of the subfamily Atelinae, family Atelidae. Like other atelines, they are found in tropical forests of Central and South America, from southern Mexico to Brazil. The genus consists of seven species, all of which are under threat; the brown spider monkey is critically endangered. They are also notable for their ability to be easily bred in captivity.
Mud dauber is a name commonly applied to a number of wasps from either the family Sphecidae or Crabronidae which build their nests from mud; this excludes members of the family Vespidae, which are instead referred to as "potter wasps". Mud daubers are variable in appearance. Most are long, slender wasps about 1 inch (25 mm) in length. The name refers to the nests that are made by the female wasps, which consist of mud molded into place by the wasp's mandibles. Mud daubers are not normally aggressive, but can become belligerent when threatened. Stings are uncommon.
Anisogamy is a form of sexual reproduction that involves the union or fusion of two gametes that differ in size and/or form. The smaller gamete is male, a sperm cell, whereas the larger gamete is female, typically an egg cell. Anisogamy is predominant among multicellular organisms. In both plants and animals, gamete size difference is the fundamental difference between females and males.
The organ pipe mud dauber is a predatory wasp in the family Crabronidae. It is fairly large, ranging from 3.9–5.1 cm, and has been recorded to fly from May to September. Females and males are similar in colour, a shiny black, with the end part of the back leg being pale yellow to white. The organ pipe mud dauber feeds mainly on three genera of spider: Neoscona, Araneus, and Eustala. Melittobia, a parasitoid wasp, is a common ectoparasite of T. politum prepupae. Other sources of parasitism include the bombyliid fly Anthrax, chrysidid wasps, and various species of scavenger flies (Miltogramminae). The tufted titmouse is a known predator of T. politum, and may feed on them more commonly than previously thought, as the holes made by the titmouse are similar in shape and size to those made by T. politum leaving the nest after pupation.
The short-tailed pygmy monitor is the second smallest living monitor lizard in the world with a maximum length of 25 cm.
Symphytognathidae is a family of spiders with 90 described species in eight genera. They occur in the tropics of Central and South America and the Australian region. Exceptions include Anapistula benoiti, Anapistula caecula, and Symphytognatha imbulunga, found in Africa, Anapistula ishikawai, found in Japan, and Anapistula jerai, found in Southeast Asia.
The smallest organisms found on Earth can be determined according to various aspects of organism size, including volume, mass, height, length, or genome size.
Patu is a genus of dwarf orb-weavers that was first described by Brian John Marples in 1951. Two candidates for the "smallest species of spider", are in this genus, Patu digua and Patu marplesi.
The Pacific robin, is a red-breasted Australasian robin in the passerine bird genus Petroica found in Melanesia and Polynesia. It is similar in plumage to the scarlet robin of Australia, and until recently the two were considered conspecific until split in 1999 by Schodde and Mason. Thirteen subspecies of Pacific robin are currently recognised, and these subspecies display considerable variation in plumage, foraging preferences, and habitat. The Norfolk robin was previously considered a subspecies of the Pacific robin, but is now considered a distinct species.
Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. As of December 2023, 1,100 species have been identified, with 166 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although many other members of the same infraorder (Mygalomorphae) are commonly referred to as "tarantulas" or "false tarantulas". Some of the more common species have become popular in the exotic pet trade. Many New World species kept as pets have setae known as urticating hairs that can cause irritation to the skin, and in extreme cases, cause damage to the eyes.
A hermaphrodite is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic.
Spiders are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species diversity among all orders of organisms. Spiders are found worldwide on every continent except Antarctica, and have become established in nearly every land habitat. As of September 2024, 52,309 spider species in 134 families have been recorded by taxonomists. However, there has been debate among scientists about how families should be classified, with over 20 different classifications proposed since 1900.
Nigorella aethiopica is the type species of the genus Nigorella. A jumping spider that lives in Ethiopia and named in honour of the country in which it is found, it was first described in 2008 by Wanda Wesołowska and Beata Tomasiewicz. The spider is larger than others in the species with a cephalothorax that is between 4.1 and 4.8 mm long and an abdomen that is between 4.3 and 5.6 mm long. The carapace is generally brown and hairy, although the male is darker. While the male abdomen is marked by a light stripe on the topside and dots underneath, the female abdomen has a pattern of a light stripe and patches on the top and dark stripes on the bottom. As well as its larger size, the species can be distinguished by its copulatory organs. The split at the end of the appendage on the pedipalp tibia marks out the male, and the female has longer seminal ducts and thinner spermathecae than others in the genus.
Parabomis wandae is a species of crab spider in the genus Parabomis that lives in Ghana, Ivory Coast, Kenya and Rwanda. The species was first described in 2020 by Ansie Dippenaar-Schoeman and Stefan Foord. It thrives in rainforests. The spider is very small, with a total length between 1.9 and 2.26 mm. The female is larger and lighter in colour than the male. It has a distinctive hump to the abdomen, which for the female is less pronounced. The female abdomen has dark patches and spots on its white surface, while the male has a brown shell. The species can be differentiated from other members of the genus by its copulatory organs. The male has a distinctive beak-like end of the retrolateral tibial apophysis. The female has an egg-shaped epigyne with long copulatory ducts.
