THE GREENHOUSE THRIPS. 



47 



the head. The total length is about 1.25 mm. and the greatest 

 width, across the mesothorax, is about 0.30 mm." 



The male has not been described, and this species is without ques- 

 tion parthenogenetic for many generations. 



The egg. — The egg (fig. lG,a) is bean-shaped, 0.296 mm. in length 

 and 0.088 mm. in width, very delicate, with a thin shell, and color- 

 less. Eggs are laid in the leaf tissue of the host plant, generally on 

 the underside. 



The larva, first stage (fig. 16, h). — [Description made while larva was very young and 

 before it had commenced to feed on the plant.] Length, 0. 31 mm.; width of meso- 

 thorax, 0.10 mm. General shape fusiform; antennae, head, and legs very large in pro- 

 portion to the rest of the body. Color translucent white. Head large, quadrate; eyes 

 reddish, ocelli absent. Antennae 0.16 mm. in length; 7-8egmented ; b basal segment 

 cylindrical, short, with spine on inner side; second 

 segment twice as long as basal one and not as wide, 

 with 4 or 5 spines; third pedunculate, ringed, as 

 long as segments 1 and 2 combined, 2 long spines 

 near tip of segment; fourth pedunculate, nearly 

 twice as long as third, tip more slender than third, 

 ringed, a number of prominent sj^ines near tip; 

 fifth, sixth, and seventh slender, equal in length, 

 and together equaling the length of the fourth, each 

 with one or two small spines near the tip. Legs 

 translucent white, long. Abdomen tapering pos- 

 teriorly ; with 10 segments, the first 8 nearly equal 

 in length, ninth and tenth somewhat longer than 

 others. Each abdominal segment with longitudi- 

 nal rows of setae, the ninth with 2 and tenth with 

 4 spines that are three or four times the length of 

 the setae. 



The larva, second stage. — Length, 0.90 to 0.97 mm. ; 

 width of mesothorax, 0.22 to 0.23 mm.; shapeabout 

 same as in first stage; body long, cylindrical, sides 

 nearly parallel until fifth abdominal segment, where they begin to taper to blunt point. 

 Color of thorax and abdomen slightly yellowish, last two segments of abdomen trans- 

 lucent white; alimentary tract ])lainly indicated by the brownish color given to it by 

 inclosed food ; this extends from the metathorax to the sixth abdominal segment. Sur- 

 face of the body covered with minute granulations. Head quadrate, but with notch 

 behind the eyes on each side; eyes reddish, ocelli absent. Antennae 7-segmen ted, third 

 and fourth distinctly spindle-shaped and annulated, fifth and sixth slightly annulated, 

 and together with seventh segment quite slender. Legs translucent white. Abdo- 

 men 0.50 mm. in length, fusiform, ovipositor not formed; segments with rows of fine 

 setae, similar to those in adult, increasing in length toward posterior end, ninth and 

 tenth segments equal in length (0.059 mm.). 



The young nymph or prepupa (fig. 17, at left). — Length, 1.184 mm.; width of meso- 

 thorax, 0.3404 mm. Shape similar to adult. Head, length, 0.148 mm. ; width at eyes, 

 0.1628 mm. Head translucent white, vertex slightly yellowish, ocelli absent, head 



« For a full characterization of the genus and of the species see Hinds's Monograph 

 of the Thysanoptera, pp. 168-170. 



b After careful search the writer has been able to make out what he considers 7 seg- 

 ments in the antennae. 



Fig. 16.— Greenhouse thrips: a, Egg; 

 b, larva, first stage; c, larva, full 

 grown. All enlarged about 40 diam- 

 eters. (Original.) 



