222 MANUAL OF ZOOLOGY. 



sented by a pair of clubbed filaments, called 'halteres,' or 

 4 balancers.' Mouth suctorial. 



The Diptera constitute one of the largest of the orders of the 

 Insecta ; the House-flies (Musca), Gnats (Culex), Forest-flies 

 (Hippobosca), and Gad-flies (Tabanidce, fig. 66), constituting 

 good examples. 



OEDER IX. LEPIDOPTERA. Mouth suctorial, consisting of a 

 spiral trunk or ' antlia,' composed of the greatly elongated 

 maxillae, protected, when not in use, by the cushion-shaped, 

 hairy labial palpi. Labrum and mandibles rudimentary. Wings 

 four in number, flattened, covered with modified hairs or scales. 

 Larvae vermiform, commonly known as ' caterpillars.' 



Fig. 67. The Silver-striped Hawk-moth (Chcerocampa celerio). 



This well known and most beautiful of all the orders of 

 Insects comprises the Butterflies and the Moths {Jig- 67) ; the 

 former being diurnal in their habits, the latter mostly crepus- 

 cular or nocturnal. 



The larvae of Lepidoptera (fig. 68), commonly called 'cater- 

 pillars,' are vermiform in shape, normally composed of thirteen 

 segments, the anterior portion forming a distinct horny head, 

 with antennae, jaws, and usually simple eyes. The mouth of 

 the caterpillar, unlike that of the perfect insect, is formed for 

 mastication. The labium also is provided with a tubular organ 

 the ' spinneret ' which communicates with two internal 

 glands, the functions of which are to furnish the silk, whereby 

 the animal constructs its ordinary abode, or spins its cocoon. 

 The three segments behind the head correspond with the pro- 

 thorax, mesothorax, and metathorax of the perfect insect, 



