INTRODUCTION. 



The mosquitos, gnats, flies, ticks, and fleas constitute the order Diptcra of the class Insecta. They have 

 only two wings (a few wingless excepted) ; in place of hind wings, they have a minute hair with a knob on the 

 end of each called the balancers ; mostly covered by a scale when at rest. Their mouth parts are formed for 

 sucking or lapping, never for biting, though often enclosed in sharp horny needles for piercing; some have 

 their tongues enclosed in a s.ift trunk. Their food is always liquid. They lay their eggs inthe water, on fruit or 

 on various growing or decaying vegetable or animal matter, on which their larva-, footless maggots live. The 

 maggots when full grown transform to pupa, mostly enclosed in their own dried skin, though some times naked. 



In 1853, Dr. T. \V. Harris counted 247 kinds in Massachusetts. Now over 2500 are named, and as in Europe, 

 10,000 are known to exist, a similar number may be expected in the United States. 



Many kinds appear in countless swarms and as a veritable plague, but some are useful. 



The order Diptcra has been divided into sub-orders by the way the fly opens the pupa when leaving it; but 

 as the pupa is rarely met with, the old way of dividing the order by the various number of joints in their feelers 

 (aiiici/i/ic) is more convenient. The sub-orders are divided into families by the variations of the veins in their 



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