420 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



young and adults have a pair of sharp spines at the tip of the 

 abdomen which they use to drive away enemies by striking them 

 quickly right and left. Two or three days after birth the skin is 

 shed and another molt occurs five or six days later. With the 

 third stage the wing-pads appear. This stage lasts four days ; 

 and during it the insects take no food and remain almost quiet, 

 moving with difficulty. On onions the nymphs have been found 

 mostly on the bulbs in the loose soil. With the next molt, the 

 insect becomes mature and winged. Thus, the total life cycle as 

 observed by Professor Quaintance in Florida is about sixteen days. 

 In Russia Dr. Lindeman found that a generation required forty- 

 seven days. " In Florida there are probably no distinct broods, 

 as all stages may be found at the same time. Allowing for the life 

 cycle at sixteen days, a large number of broods could occur during 

 the year, but unfavorable conditions keep them reduced, except 

 during the spring and perhaps early summer (the worst injury 

 occurring in May and June), so that it will probably not happen 

 that they will develop throughout a year according to their capa- 

 bilities." 



Control. The pest may be successfully controlled by spraying 

 with whale-oil soap, 1 pound to 2 gallons of water, rose-leaf insec- 

 ticide, 1 pint to 4 gallons of water, or kerosene emulsion diluted 

 8 to 10 times. Tobacco decoction (see page 55) will probably 

 prove equally effective, using it as strong as necessary. Probably 

 1 pound of stems to 2 gallons of water will be satisfactory. The 

 spraying should be done very thoroughly so as to reach the insects 

 in the axils of the leaves, and the soil around the plant also should 

 be well wet to destroy the mature nymphs that may be hiding. 



The Imported Onion-maggot * 



The common white maggot which bores into the roots and 

 bulbs causing them to wilt and decay, is probably the most 

 important insect pest of the onion. The present species is by far 

 the most commonly injurious and is termed " imported " because 



* Pegomyia ceparum Bouch. Family Anthomyiidce. See same references 

 as for cabbage-maggot, footnote, page 347. 



