84 CALIFORNIA STATE COMMISSION OF HORTICULTURE. 



which are not butterflies or moths. The name "fly," however, is only 

 properly applied to members of the order Diptera. 



Considering the number of individuals and the number of species, 

 flies very greatly exceed any other order. They are common every- 

 where, in the houses, fields, swamps, and plains. Their members swarm 

 in every place ever penetrated by man. Within this order are some of 

 the most serious pests with which we are troubled, and they attack 

 alike our animal and vegetable products, and man himself suffers more 

 from them than from any other of the orders. We can escape in some 

 manner our insect enemies in the other orders, but not always the 

 Dipterous. 



In this order we have the mosquito family, some members of which 

 spread disease and death in the germs of yellow fever and malaria. 

 It may be safely asserted that this family alone is the source of greater 

 suffering, hardship, and even death to mankind than any other one 

 cause. This order, too, furnishes the dreaded fruit-flies, one of the most 

 destructive pests with which the fruit-grower has to cope, and which 

 fortunately has not yet obtained a foothold in California. The disrep- 

 utable botfly; the sheep-tick, a wingless form; the Hessian-fly, which 

 causes a loss to the farmers of the United States of $100,000,000 

 annually; the ox warble fly, which causes a loss as high as $40,000,000 

 on hides, and others too numerous to mention, but most injurious to a 

 greater or less extent, all belong to this order of two-winged flies. At 

 the same time, there are many of its members which are friendly to 

 man and which give us some of our most valuable beneficial insects. 

 Among these are the Tachnid flies, one of which is the principal check 

 on the locusts, and without whose work California would suffer severely 

 every season from the locust pest. The Syrphus flies are another of 

 our friendly families which feed upon the aphids and serve largely to 

 keep them down. 



As indicating the vast numbers of this order, it may be stated that 

 there are already over 40,000 described species, and it is estimated that 

 this number would be increased to 350,000 if all the species were known. 

 All the members of this order are suctorial insects, and their mouth 

 parts are formed to this end. The methods of different species in pro- 

 curing their food, however, differ widely. Some simply absorb fluids, 

 or reduce their food to a fluid state, in order to absorb it, as with the 

 house-fly; others are provided with a piercing beak, with which they 

 are enabled to drill a hole into their victim and suck his blood, as with 

 the mosquito. Some absorb the juices of vegetables, others of animals, 

 and others again have no choice but to take whatever comes handiest- 

 The larvae of flies are known as maggots. They are usually footless 

 grubs, and pass through a perfect transformation. In some cases the 

 eggs hatch within the body of the female, and the young maggots are 



