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The insect order Zoraptera, commonly known as angel insects, contains small and soft bodied insects with two forms: winged with wings sheddable as in termites, dark and with eyes (compound) and ocelli (simple); or wingless, pale and without eyes or ocelli. They have a characteristic nine-segmented beaded (moniliform) antenna. They have mouthparts adapted for chewing and are mostly found under bark, in dry wood or in leaf litter.
The members of this order are small insects, or less in length, that resemble in appearance and in their gregarious behavior. They are short and swollen in appearance. They belong to the hemimetabolous insects. They possess mandibulated biting mouthparts, short cercus (usually 1 segment only), and short antennae with 9 segments. The abdomen is segmented in 11 sections. The maxillary have five segments, labial palps three, in both the most distal segment is enlarged. They have six Malpighian tubules, and their abdominal ganglia have fused into two separate ganglionic complexes. Immature nymphs resemble small adults. Each species shows polymorphism. Most individuals are the apterous form or "morph", with no wings, no eyes, and no or little pigmentation. A few females and even fewer males are in the alate form with relatively large membranous wings that can be shed at a basal fracture line. Alates also have and ocelli, and more pigmentation. This polymorphism can be observed already as two forms of nymphs. Wingspan can be up to , and the wings can be shed spontaneously. When observed, wings are paddle shaped and have simple venation. Under good conditions the blind and wingless form predominates, but if their surroundings become too tough, they produce offspring which develop into winged adults with eyes. These winged offspring are then able to disperse and establish new colonies in areas with more resources. Once established, future generations are once again born blind and wingless.
The following cladogram, based on the molecular phylogeny of Wipfler et al. 2019, places Zoraptera as the sister group of Dermaptera (earwigs); Zoraptera and Dermaptera together form the sister group of the remaining Polyneoptera:
Centrozoros gurneyi lives in colonies which range in size from a few dozen to several hundred individuals, but most often number about 30 individuals. The males are slightly larger than the females, and they fight for dominance. The Other Insect Societies
When two colonies of Usazoros hubbardi are brought together experimentally, there is no difference in behavior towards members of the new colony. Therefore, colonies in the wild might merge easily. Winged forms are rare. The males in most colonies establish a linear dominance hierarchy in which age or duration of colony membership is the prime factor determining dominance. Males appearing later in colonies are at the bottom of the hierarchy, regardless of their body size. By continually attacking other males, the dominant male monopolizes a harem of females. The members of this harem stay clumped together. There is a high correlation between rank and reproductive success of the males.
Latinozoros barberi lack such a dominance structure but display complex courtship behavior including nuptial feeding. The males possess a cephalic gland that opens in the middle of their head. During courtship they secrete a fluid from this gland and offer it to the female. Acceptance of this droplet by the female acts as behavioral releaser and immediately leads to copulation.
In Spermozoros impolitus, copulation does not occur, but fertilization is accomplished instead by transfer of a spermatophore from the male to the female. This spermatophore contains a single giant sperm cell, which unravels to about the same length as the female herself, . It is thought that this large sperm cell prevents fertilization by other males, by physically blocking the female's genital tract.
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