122 INTRODUCTION TO CLASSIFICATION. 



f. The Libellulidee, or Dragon-flies, have well-developed 

 jaws and are predaceous carnivores. The wings are similar, 

 membranous and reticulated. 



The larvae are provided with tracheal gills, and are as 

 predaceous as the imagines ; the labrum being converted 

 into a peculiar mask-like apparatus. 



The wings of the Libellulidge are moved by muscles 

 which are attached directly to them ; and the males have a 

 peculiar copulatory apparatus attached to the ventral 

 portion of the second somite of the abdomen. 



Three groups of insects, with incomplete metamorphosis, 

 remain, which do not fit well into any of the preceding assem- 

 blages 



a. The Physopoda, comprising the genus Thrips and 

 its allies, have a proboscidiform mouth, styliform man- 

 dibles, and maxilke united with the upper lip. Both maxil- 

 lary and labial palpi are developed ; the wings are similar 

 and unfolded. 



&. The Thysanura have biting jaws, no wings, and scaly 

 bodies. ^Some possess a peculiar springing apparatus de- 

 veloped from the abdomen. 



The genera Lepisma andPodura belong to this division. 



c. The Mallophaga, or Bird-lice, have masticatory jaws, 

 are devoid of wings, and live parasitically, chiefly upon 

 birds, whose feathers they devour. 



The MYRIAPODA are divided into two orders 



1. The CHILOPODA (Centipedes) have the head and the seg- 

 ments of the body broad and depressed, and each segment bears 

 only one pair of limbs, which are separated by a broad sternum. 



The aperture of the organs of reproduction is situated at 

 the posterior extremity of the body, and the males have no copu- 

 latory organs. 



2. The CHILOGNATHA (Millipedes) have the head and seg- 

 ments of the body rounded or compressed. All but a few of the 

 most anterior segments bear two pairs of limbs, attached close 

 together upon each side of the middle line. 



