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11. 



D I P T E R A. 



All suctorial insects which in the perfect state possess only two 

 membranous wings, are called Diptera, from two Greek words — 

 5«, twice, and Trrephu, wing. 



The Diptera were known and scientifically described at a very 

 early date. They are frequently mentioned by Aristotle in his 

 "History of Animals;" and he applied the term to the same insects 

 as now constitute the order. 



The absence of the second wings, common to other insects, which 

 are in this case replaced by two appendages, which have received 

 the name of balancers,* because they serve to regulate the action of 

 flight, constitutes the chief characteristic of the Diptera. Let us, 

 however, give a glance at their other organs, which have more or 

 less affinity with those which exist in other classes of insects, pre- 

 serving, nevertheless, their own especial characteristics. 



The mouth, for instance — suited for suction only — is in the form 

 of a trunk, and is composed of a sheath, a sucker, and two palpi. 

 The antennae are generally composed of only three joints. The eyes 

 — usually two in number — are very large, and sometimes take up 

 nearly the whole of the head. They are both simple and compound. 

 The wings are membranous, delicate, and veined ; the limbs long 

 and slight. In giving the history of the principal types of Diptera, 



I We shall explain more fully the formation of these organs. 



j The Diptera, by their rapid flight, enliven both the earth and the 



I air. The different species abound in every climate, and in every 

 situation, some inhabiting woods, plains, fields, or banks of rivers ; 

 others preferring our houses. They like the neighbourhood of vegeta- 



' tion, choosing either the flowers, the leaves, or the stems of the trees 

 of our woods, our gardens, or our plantauons. Their food varies 



* Sometimes called halicns. — Ed. 

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