600 INSECTS AT HOME. 



legs below, and the balancers above. These organs, which are 

 the rudiments of tlie under wings, are generally shaped like 

 tiny bristles tipped with a round knob, and they are furnished 

 with muscles by which they can be kept in a state of rapid 

 vibration. So important are these organs that, even in those 

 Diptera in which the upper wings are wanting, the halteres are 

 present. 



Their small size renders them useless for the purposes of 

 flight, but it has been pi-oved that they serve in some mode to 

 guide the flight — how, it is not easy to say. The ordinary 

 shape of these balancers can be seen by reference to the insect 

 which is represented on Woodcut LXX. The word ' halteres ' is 

 Grreek, and signifies an adjunct to gymnastics, which has long- 

 been abandoned. Those athletes who competed for the wide 

 jump, used to take in their hands the halteres ; i.e. a pair of 

 iron and leaden weights, and, as they made the spring, they 

 swung the arms forward, so that the impetus of the weights 

 should add to the force of their leap. They were also employed 

 of a larger size, for the purpose of exercisir.g the arms, much as 

 we use dumb-bells. 



Other peculiarities of this Order of Insects will be mentioned 

 in the course of the following pages. 



With regard to the arrangement of these insects, there has 

 been much controversy between systematic entomologists, and 

 much yet has to be done in this respect. As, however, this is 

 not a purely systematic work, but deals more with the actions 

 than the comparative anatomy of insects, we will accept the 

 system of Professor Westwood, a system which he has elaborated 

 with great labour and skill. He divides them first into two 

 great Sections, the first of which he calls Cephalota, because 

 the head is quite distinct from the thorax, and not sunk into 

 it. The larva undergoes its transformation without the body of 

 the parent, and the claws of the tarsi are not toothed. The 

 first of these definitions, however, is quite sufficient to enable 

 the observer to know in which section he ought to place any fly 

 that may come before him. 



This section he again separates into two Divisions, the first 

 of which is the Nemocera, or Thread-horned Diptera, in which 

 the antennae have more than six joints, and the palpi have 



