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Tracheal stigmata. 
One of the most important characters in Urothrips lies in the 
tracheal system, our species possessing no less than eleven pairs 
of stigmata; the pro-mesothoracic and meso-metathoracic pairs and 
a pair in each of the abdominal segments one to nine. These 
stigmata are all large and very distinct. 
In all other forms of Zubul:fera we find only four moderately 
large pairs of stigmata, the two first named, and a pair on the first 
and eighth abdominal segments, whilst in the Zereörantia the 
stigmata are smaller and usually four in number, though the meso- 
metathoracic pair are often very small, vestigial, and sometimes 
apparently totally absent. We have only examined a few species 
of Æolothripidæ, in which the stigmata present have been very 
small, and as yet we have personally been unable to trace the 
fourth (the meso-metathoracic palr) pair in this family. We should 
have preferred to have had the time and opportunity to examine 
more material in this family before making use of this observation, 
and can only incorporate it with reservation. 
These facts and observations give rise to an interesting table : 



FAMILIES. STIGMATA. PALPI. 
Tubulifera. 
Urothripide BAGNALL. . . .| 11 pairs very large. | Both pairs 1-jointed. 
Phleothripide HALIDAY . . . 
4 pairs usually large | Both pairs always 
Idolothripide BAGNALL . . . 2-jointed. 
Terebrantia. 
Thripide HALIDAY. . . . .| Usually 4 pairs,small; | Maxillary pair simple, 
meso - metathoracic 2- or 3-jointed. 
pair often very | Labial pair always 
small, vestigial, or 2-jointed. 
altogether absent. 

Æolothripidæ HALIDAY . . .| 3 pairssmall; meso- | Maxillary pair genicu- 
metathoracic pair | late, 3- to 7-jointed. 
apparently absent. | Labial pair 2-, 4- or 5- 
jointed. 
