330 APPLIED ENTOMOLOGY 



sisting of many acres having nearly every onion affected. It varies 

 greatly in importance in different years, however, there being in some 

 seasons practically no maggots. 



Control. — The adult flies feed freely both before and during the 

 egg-laying period. Making use of this fact, a poisoned bait spray issued, 

 consisting of 3^^ oz. of white arsenic or sodium arsenate dissolved in 1 gal. 

 of boiling water to which is then added from 3^^ to 1 pint of strong- 

 smelling molasses. This is sprayed in coarse drops in strips across the 

 field, it not being necessary to cover the entire area in this way. Repeat 

 twice a week from the time the onions show until the middle of June. 

 This treatment has given good results but the cost of the labor involved 

 in so many applications is considerable. 



Other members of this family are frequently injurious, and, among 

 these, the Seed-corn Maggot, often attacking peas and beans also, the 

 Beet and Spinach Leaf-miner and the Radish Maggot may be mentioned. 

 Methods of control for these insects are at present far from being as 

 satisfactory as could be desired. The Lesser House-fly and several 

 other small, house-inhabiting flies which belong here are also of some 

 importance as probably being disease carriers. 



There are several families of extremely modified aberrant forms 

 which are generally classed together as a suborder of the Diptera called 

 the Pupipara. Some of these insects are winged while others are wing- 

 less when adult. The majority of them suck the blood of birds or mam- 

 mals though one species not thus far reported from America is found 

 on the body of the honey bee. Swallows appear to be favorite hosts 

 for some of these insects and bats for others, while the most familiar 

 insect belonging here lives on the sheep and is commonly called the 

 Sheep Tick. A number of others of the group, are also wrongly called 

 ticks, probably because of their color which is similar to that of some 

 common ticks, their leathery external skin, and the places where they 

 are found. True ticks have eight legs, however, and never have wings, 

 while six legs only are present in the Pupipara as with the other insects. 



The Sheep Tick {Melophagus ovinus L.). — This pest of sheep is a 

 wingless, brown insect about a quarter of an inch long. It occurs in 

 most of the countries where sheep are raised and is present practically 

 wherever sheep are found in the United States, though most abundant 

 in the West in the large flocks. The adult lives in the fleece of the host 

 except when feeding, at which time it moves to the surface of the skin 

 of the animal, punctures it and sucks the blood and lymph causing irrita- 

 tion which, when many of the insects are present, makes the sheep rest- 

 less, preventing their feeding considerably, and resulting in their failure 

 to grow and fatten as they should. 



The adult (Fig. 351) does not deposit eggs, these being retained within 

 the body of the parent until they have hatched into larvae (Fig. 352) and 



