128 Invertebrata. 



parasites which live on the abdomen of bees and 

 wasps. In these the males have four wings, two in front, 

 small and twisted, from which the order is named, 

 two behind, large and fan-like ; the females never lose 

 their last pupa-skin, and are wingless, with a worm-like 

 abdomen and are viviparous. 



ORDER IX. Aphaniptera. Includes fleas which 

 have laterally compressed bodies and exceedingly 

 rudimental wings, the scale-like traces of which are 

 with difficulty noticeable. The suctorial mouth (fig. 

 66), without upper lip, has long slender saw-like 

 mandibles, which are sheathed by the three-jointed 

 labial palps at their base. 



The antennae are very small and lie in a groove, 

 but the maxillary palps are large and prominent. The 

 hindmost pair of limbs are long, muscular, and well- 

 fitted for leaping. The larvae are white footless grubs 

 which feed on animal matter for about twelve days, spin 

 for themselves a cocoon, and pass to the pupa stage. 

 After about fourteen days' quiescence in this stage the 

 perfect insect emerges. In many respects the flea is 

 closely allied to the next order. 



ORDER X. Diptera, two winged flies, including 

 flies, gnats, mosquitoes, &c. In this order the hind 

 pair of wings is rudimental and represented by scale- 

 like or pin-like processes under the developed pair of 

 wings, and the mouth is a proboscis. The larvae are 

 footless, often headless maggots, such as are found on 

 putrid meat. Some forms of Diptera, like the gnats 

 and mosquitoes, are provided each with a long pro- 

 boscis enclosing six long sharp bristles. The larvae of 

 the gnats are aquatic and breathe air by means of a 



