THE GREENHOUSE THRIPS. 45 



attacked, soon after unfolding. The infested leaves first showed 

 injury on the underside, where the surface appeared full of minute 

 white spots. As attack continued, these spots became more numer- 

 ous and united, forming blotches where the leaf was devoid of tissue. 

 The injury then became apparent from the upper side, as the surface 

 developed a twisted and distorted aspect between the lateral veins, 

 and was finally evidenced l)y wilted and dead areas around the edges 

 of the leaf. In severe attacks the insects spread to the upper sur- 

 face of the leaves, and in a short time this as well as the underside is 

 nearly devoid of color. Both surfaces become thickly covered with 

 minute drops of reddish fluid voided by the thrips, which gradually 

 change to black. As the attack continues, the leaves become limp and 

 yellow- and eventually drop off. so that plants that were not treated 

 to prevent injury in many cases lost their entire "foliage. The injury 

 is similar on other ornamentals. 



This insect injures plants in two ways: First, it causes a serious 

 drain on the vitality of the plant from the feeding of thousands of 

 thrips, so that the growth is seriously checked and in neglected cases 

 wx)ul(l cause the death of the plant. Secondly, it destroys the beauty 

 of the plants for ornament by despoiling them of their foliage. 



ORIGIN AND DISTRIBUTION. 



Although this insect was first described from Europe and is there 

 widely distributed, it is without doubt indigenous to tropical i\jnerica. 

 Pergande'^ writes that this insect was ''probabh^ introduced with 

 ornamental plants from the warmer regions of America:" and that it 

 "is found upon wild and cultivated plants in Brazil." Franklin" 

 records it in Barbados as follows: "This species is found in the open 

 in St. Vincent and Barbados. It is evidently a tropical species." 

 This insect has been collected at Miami, Fla. , on plants growing in the 

 open in midwinter. Moulton^" says, "out of doors it feeds and be- 

 comes very destructive to Laurestinas." Mr. Condit, WTiting of this 

 species from Santa Barbara, Cal., November 2, 1908, said that it was 

 doing considerable damage to ornamentals in one of the parks. 



These records of occurrences at several localities in the Tropical anil 

 I-«ower Austral life zones of this country point strongly to tropical 

 America as its origimd home. This is further strengthened because 

 of its well-known habit of living in greenhouses, in many localities, 

 upon exotic plants from the Tropics. From this habit it has become 

 widely distributed in Europe and North America. In Europe, Walker 

 and Cameron record it from several places in England, Bouchc ami 

 others from Germany, Ileeger and Low from "N^ienna, and Renter 

 from Finland. It has also been recorded from France and Italy. 



In this country it has been recortled from Massachusetts, from 

 several places in Michigan, and from Washington, D. C., Floritla, and 



