Protura And Thysanura

Proturans: Order Protura

Identification: Minute whitish insects, 0.6-1.5 mm. Eyes, wings, cerci, and antennae lacking. Front legs carried in an elevated position like antennae. Abdomen of adult 12-segmented, with a pair of short styli (fingerlike processes) on each of the 3 basal segments. Metamorphosis simple.

Similar orders: Other minute wingless insects have less than 12 abdominal segments, and either have antennae or lack styli on the 3 basal abdominal segments.

Immature stages: Similar to adult stage, but with fewer abdominal segments (a segment added each molt).

Habits: Proturans occur in moist soil, moss, leaf mold, under bark, and in rotting wood. They are rather rare, and are very infrequently collected.

Importance: This order is considered to be a very primitive one.

Its members are not of economic importance.

Classification: Three families, separated principally on the basis of the presence or absence of a tracheal system and the character of the abdominal appendages.

Key to Families

1. Tracheae present, with , 2 pairs of spiracles on thorax; abdominal appendages with a terminal vesicle

Eosentomidae

V. Tracheae and spiracles absent; abdominal appendages with or without a terminal vesicle 2

2(1'). At least 2 pairs of abdominal appendages with a terminal vesicle Protentomidae

2'. Only the 1st pair of abdominal appendages with a terminal vesicle Acerentomidae

Bristletails: Order Thysanura

Identification: Elongate (rarely oval) wingless insects with 2 or 3 tail-like appendages at end of abdomen. Some abdominal segments with a pair of styli (fingerlike processes). Antennae long and many-segmented. Metamorphosis simple. Similar orders: (1) Protura: no antennae or tails; minute size (Thysanura usually more than 1.5 mm.). (2) Collembola (p. 62): no tails, but usually a forked appendage at end of abdomen; no styli on abdomen, but generally a single short tubular structure (collophore) on 1st segment; antennae short. (3) Orders of Ptery-gota (larvae and wingless adults), p. 56: no styli on abdominal segments.

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