114 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvi. 



ment is frequently held by the hairs around the anus. The larva? are 

 less active than the adults and have no power of springing. The lar- 

 val antenna always has fewer segments than the adult. In Phlreo- 

 thripidffi the number is constantly seven. Thickened femora and tar- 

 sal hooks do not occur, the tarsus appears to be one segmented, and 

 claws may or may not be present. The structure of the foot is nuu-h 

 more distinct than in the adult. The eyes are not compound, l)ut com- 

 posed of a few separated facets, which are strongly elevated and always 

 circular i n outline. The number of facets increases in successive molts, 

 but the circular form is retained. The rudiuients of the ovipositor or 

 genital apparatus appear on the under side of the eighth and ninth 

 segments as indistinct lobes. The food habits of the larvtv are just as 

 varied as are those of the adults, and some species are also found upon 

 the roots of plants. 



J/<>/?'.v. — From two to four molts appear to occur while in the larval 

 stage, the last marking the change to the pupa. The chitinous cover- 

 ing of the internal mouth parts and of the bladders can be distinctly 

 seen in the cast skin. When larvw have become full grown they 

 cease to feed, become restless, and seek some very secluded place in 

 which to molt. In this search they are so successful that in many 

 species pupee are hard to find. 



Nijnqyh nr Pupa. — The metamorphosis of Thysanoptera is peculiar, 

 for though complete in many respects, it is nmch less so in others. 

 Two stages are distinguishable while in the nymph condition. After 

 the last larval molt, the insect still retains its larval appearance, the 

 antennie are extended, and the pro-nymph is moderately active. The 

 wing pads are partially developed, extending to al)out the second 

 abdominal segment, and the beginning of the formation of the adult 

 appendages can be seen. After another molt, the true nymph stage is 

 reached and the animal remains quiet unless disturbed, when it is 

 capable of slight movement. No food is taken during this ]5eriod. 

 The antenna? are laid back upon the head and prothorax; their seg- 

 mentation has become indistinct and the adult antenna can be seen 

 within the nymphal skin. The numl)er of facets in the eyes greatly 

 increases, producing the adult condition. The logs are inclosed in 

 loose sheaths and the wing pads reach to and from the sixth to the 

 eighth segments. The pads extend obliquely outward along the sides 

 of^the body and do not cover each other. The fringes appear along 

 the edges of the forming wings, the fore fringe being directed to\vard 

 the tip and hind fringe toward the base of the wing. The forming 

 lobes representing the ovipositor elongate, and those on each side over- 

 lap l)ut remain separate. Within them develop the pointed valves of 

 the adult ovipositor, which now extends to ,tho tip of the abdomen. 

 The development of the male genital apparatus takes place in a very 

 similar way to that of the ovipositor of the female. The nymph stage 



