9 The Panorpoid Orders 1. Introduction In this and the following chapter we shall deal with the endopterygote insects—those that have a distinct pupal instar in which the insect undergoes a drastic metamorphosis from the larval to the adult form. | 9 The Panorpoid Orders 1. Introduction In this and the following chapter we shall deal with the endopterygote insects those that have a distinct pupal instar in which the insect undergoes a drastic metamorphosis from the larval to the adult form. As noted in Chapter 2 Section considerable difficulty has arisen in deciding whether the endopterygote orders have a common origin or are polyphyletic. The five orders considered in this chapter Mecoptera Diptera Siphonaptera Trichoptera and Lepidoptera show clear affinities that enable them to be grouped together as the panorpoid complex. Within the complex there are two sister lines of evolution the Antliophora first three orders and the Amphiesmenoptera Trichoptera and Lepidoptera . The remaining orders Megaloptera Raphidioptera Neuroptera Coleoptera Hymenoptera and Strepsiptera dealt with in Chapter 10 show few affinities with the panorpoid group. 2. Mecoptera Synonyms Panorpatae Panorpina Panorpida Common name scorpionflies Slender medium-sized insects head usually prolonged ventrally into a broad rostrum with long filiform antennae well-developed compound eyes and biting mouthparts usually with two pairs of identical membranous wings with primitive venation and carried horizontally at rest abdomen with short cerci and in males prominent genitalia. Larvae usually eruciform with simple eyes biting mouthparts and thoracic legs abdominal legs present or absent. Pupae decticous and exarate. This is a small order containing about 500 known species about 90 of which belong to two families Panorpidae and Bittacidae. The order is particularly common in the Northern Hemisphere and includes about 75 North American and 4 British species. About 30 species occur in Australia. 239 240 Structure CHAPTER 9 Adult. A characteristic feature of most Mecoptera is the ventral prolongation of the head into a broad rostrum. Incorporated into this structure are the clypeus labrum and maxillae. Compound eyes are well developed and in most
