PREFACE. XIX 



the Mandibulata the generic name of Nirmus, which was 

 retained in the works of several subsequent writers. In 

 1806 Latrielle gave the world his " Genera Crustaceorum 

 et Insectorum," in which, under the Order Parasita, which 

 he had instituted in 1796, he arranged both Pediculi and 

 Nirmi, the first as a family denominated Edentula, the se- 

 cond Mandibulata. In 1815 Lamarck published that part 

 of his Histoire Naturelle des Animaux sans Vertebres, which 

 contained insects, arranged with slight variations, according 

 to a system he had propounded many years before, in which 

 the Hexapod aptera are placed with the Arachnidae. The 

 Haustellate species as the Genus Pediculus ; the Mandi- 

 bulate as the Genus Ricinus. In the same year Dr. Leach 

 published in the Edinburgh Encyclopaedia an arrangement 

 of insects into orders, and placed them with the Parasita 

 and Thysanura (which Lamarck had removed to the Arach- 

 nida), the former constituting a new order, Anoplura, in 

 which the Suctorial group is sub-divided into three genera 

 Phthirius, Pediculus, and Hcematopinus ; the masticating 

 group, remaining under the Genus Nirmus. In 1818 Dr. 

 Nitzsch published in Germar's Magazine der Entomologie, 

 a Prodromus of the families and genera of Animal Insects 

 (Insecta epizoica), in which an extensive sub-division of the 

 Nirmi is effected, the characters of genera and sub-genera 

 laid down, and upwards of eighty species enumerated, the 

 order Aptera is abolished, and the wingless genera located 

 under such other orders as they appear to be most nearly 

 allied to : thus the Mandibulata with the Orthoptera, and the 

 Haustellata with the Hemiptera. In 1821 MacLeay's Horae 

 Entomologicae appeared, a work exhibiting a profound know- 

 ledge of the natural affinities and analogies of the whole of 

 the Annulose tribes. In this system the Pediculidae and Nir- 

 midae underwent little or no change as to rank. The class 

 Insecta is sub-divided into three supposed equal sub-classes 

 Mandibulata, Haustellata, and Ametabola, in the last 



