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.
Description
The name Zoraptera, given by Filippo Silvestri in 1913, is misnamed and potentially misleading: "zor" is Greek for pure and "aptera" means wingless. "Pure wingless" clearly does not fit the winged alate forms, which were discovered several years after the wingless forms had been described.
The members of this order are small insects, or less in length, that resemble termites 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 cerci (usually 1 segment only), and short antennae with 9 segments. The abdomen is segmented in 11 sections. The maxillary palps 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 compound eyes 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 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. The wings are paddle shaped, and have reduced venation.
Systematics
Phylogeny
The phylogenetic relationship of the order remains controversial and elusive. At present the best supported position based on morphological traits recognizes the Zoraptera as polyneopterous insects related to the webspinners of the order Embioptera. However, molecular analysis of 18s ribosomal DNA supports a close relationship with the superorder Dictyoptera. There are eleven extinct species known as of 2017, many of the fossil species are known from Burmese amber.
Classification
The Zoraptera are currently divided into two families, four subfamilies, nine genera and a total of 51 species, some of which have not been yet described.
Family Zorotypidae
Subfamily Zorotypinae
Zorotypus — 7 spp. Usazoros — 1 sp. Subfamily Spermozorinae Spermozoros — 6 spp. Family Spiralizoridae Subfamily Latinozorinae Latinozoros — 3 spp. Subfamily Spiralizorinae Spiralizoros — 12 spp. Centrozoros (=Meridozoros ; Floridazoros ) — 8 spp. Cordezoros — 1 sp. Scapulizoros — 1 sp. Brazilozoros — 3 spp.
Incertae sedis
The following nine species are considered Zoraptera incertae sedis:
Zorotypus congensis
Zorotypus javanicus
Zorotypus juninensis
Zorotypus leleupi
Zorotypus longicercatus
Zorotypus newi (=Formosozoros newi ) Zorotypus sechellensis Zorotypus swezeyi
Extinct taxa
†Xenozorotypus Engel & Grimaldi 2002
†Xenozorotypus burmiticus Engel & Grimaldi 2002 - Burmese amber, Myanmar (Cretaceous)
Behavior and ecology
Zorapterans live in small colonies beneath rotting wood, lacking in mouthparts able to tunnel into wood, but feeding on fungal spores and detritus. These insects can also hunt smaller arthropods like mites and collembolans.
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.