24 INSECTS AND MAN 



aquatic, and, among them, we may mention the dragon flies, 

 May flies, and stone flies. 



(d) Hymenoptera (membrane wings), bees, ants, wasps, 

 etc., with four membranous, slightly veined wings, and 

 biting and sucking mouths. 



This is a large and important order, and a review of all 

 the families is impossible, so we will mention some of the 

 groups more frequently encountered. The bees, Apidce, are 

 the most important members of the order, and, in addition 

 to the honey bee, there are many equally interesting, though 

 less important, insects, such as the leaf -cutter bees, Mega- 

 chile. They form burrows and line them with pieces of 

 leaf which they cut from plants. The carpenter bees, 

 Xylocopa, are also of great interest, their nests being a 

 series of chambers in some plant stalk, in each one of which 

 they place bee bread and an egg. 



The ants, Formicidce, have been the subject of much 

 research, mainly on account of their remarkable intelli- 

 gence ; but they must not be confounded with the related 

 "cow ants," Mutillidce. Other members of the order are 

 the sand wasps, Pompilidce, which form burrows in the 

 ground and store them with insects, previously rendered 

 unconscious, but not lifeless, by a sting, so that their larvae 

 when they appear may have living food. The Vespidce, of 

 which the common wasp is a member, are well known to 

 everyone. The saw flies, Tenthredinidce, are so called be- 

 cause the females are provided with a curious saw-like 

 appendage with which to cut leaves of plants, preparatory 

 to ovipositing therein. Of the other Hymenoptera we may 

 mention the Chalcididce and Proctotrypidce gall-producing 

 and gall-destroying insects, and the Braconidce and Ich- 

 neumonidce parasites, with a habit of laying their eggs in 

 the bodies of other insects. 



(e) Coleoptera (sheath wings), beetles, have four wings, 

 the upper pair horny ; their mouth parts are designed for 

 biting. 



