THE GREENHOUSE THRIPS. 51 



The piipiv are associated w iili tlie prepiipae, but do not move about 

 unless disturbed. Not only are the prepupse more active than the 

 pupa?, but the}' carry the antennce in front of the head and frequently 

 move them, while the pupae have the antennae laid back on the head 

 and motionless. Neither prepupae nor pupjie take any nourishment. 



FOOD PLANTS." 



IleliotJirijys hsemorrhoidalis feeds on a large number of ornamental 

 plants. In this country it has been recorded as feeding on the fol- 

 lowing: Liliaceous plants, azalia, Pellea hastata, aspidium, crotons, 

 dahlias, phlox, verbena, pink, ferns, vines, cherry laurel, lauristina, 

 palms, ficus, and fuchsia. 



This year this thrips damaged the mango {Mangifera indica) at 

 Miami, Fla., and was recorded " from St. Vincent and the Barbados 

 Islands on cacao, kola, and the date palm. In Europe the following 

 hst includes most of the ornamentals preyed upon by this thrips: 

 yErides, azalia, begonia, camarotes, catleyia, crinums, dendrobuim, 

 eucharis, ficus, grape, helia, lefortia, marcintacia, pancratium, pha- 

 lenopsis, and viburnum. 



LIFE HISTORY. 



In order to study the life history of this insect, solitary females were 

 put on isolated plants that were previously uninfested and carefully 

 watched. An attem[)t to study isolated females, in small vials with 

 bits of leaves, failed of results and after 2 weeks was discontinueil. 



Life cycle. — The life cycle, as detailed, is probably very near the 

 maximum length, as the studies were conducted with the temperature 

 of the house quite low, frequently falling to 50° F. at night. With these 

 conditions the length of the egg stage is about 8 days, but possibly in 

 a well-heated greenhouse this would be cut almost in half. The larvae 

 molt twice, the last time transforming to prepupa?, and tluring the 

 cool weather require from 16 to 20 days to obtain full growth. The 

 prepupal period is of short duration, occupying only from 10 to 15 

 hours, while the pupal period is from 4 to 5 days. This gives a total 

 of 33 days as a maximum, and with favorable conditions this is 

 probably reduced to 20 days or less. 



Longevity. — The greenhouse thrips, for such a minute insect, has 

 quite an extended duration of life and evidently feeds on the leaves 

 for a number of days before starting egg-deposition. In one case ob- 



« Since the above was submitted for publication some new food plants for this species 

 have been reported. Dr. E. A. Back found it feeding on maples at Orlando, Fla., and 

 on alligator pear {Persea gratissima). The fact that this insect feeds on the mango and 

 alligator pear serves to indicate that at .«ome lime in the future it may be of great im- 

 portance in Florida, as both are valuable fruits in that State. 



