812 A. E. Verrill — The Bermuda Islands. 



Physopodc or Thysanoptera. (Thrips.) 



Onion Thrips; Tobacco Thrips. (Thrips tabaci.) Figure 187. 



This very small insect is sometimes so abundant as to do consid- 

 erable damage to the onion crop, its bites causing the leaves to turn 

 yellow and wither, thus stopping the growth of the bulbs. It 

 spreads very rapidly through the onion fields. The larva is whitish, 

 but the body of the winged imago is blackish. It is very active. 

 Probably spraying with kerosene emulsion is the best remedy, but it 

 should be repeated two or three times at short intervals, in order to 

 reach all of them, for the winged insects can fly away some distance 

 when disturbed and thus many may escape. Solutions of copperas, 

 etc. are used as a spray both against the thrips and the fungous 

 disease. It is considered the same as the thrips that often does 

 much damage to tobacco. 



This insect was first recorded as occurring on the onion in Ber- 

 muda by A. G. ShipW, Bull. No. 10, p. 18, Miscell. Information, 

 Royal Kew Gardens, 1887. For full descriptions of adult and larva, 

 see Th. Pergande, Insect Life, vii, p. 391-3; and W. E. Hinds, Proc. 

 U. S. Nat. Mus., xxvi, p. 179, pi. vii, figs. 69-71, 1902. 



It not only attacks onions and tobacco, but also many other culti- 

 vated plants, including melons, cucumber, squash, turnip, cabbage, 

 cauliflower, parsley, and many flowering plants. Its effect on onions 

 is sometimes called " white blast." 



In the United States it was first recorded on onions in Massa- 

 chusetts, and as having been known as early as about 1857. It has 

 long been known as injurious to tobacco in Europe. 



Jc. — Pseudoneuroptera. 



Odonata ; Pragon-Jfies. 



A considerable number of Dragon-flies, some of them large and 

 haiidsomely colored, are found in summer. Their larvae must be 

 very useful in destroying the larva? of mosquitoes in the marshes 

 and tanks. Whether part of them were introduced by man is uncer- 

 tain, but there is no reason to doubt that the larger and stronger- 

 winged species might fly directly from the United States, as do 

 some of the butterflies, and thus they may have arrived indepen- 

 dently of man. The larvae or eggs of others may have been brought 

 in the water-casks of vessels, and in other ways. 



