308 Rerorr or THE DEPARTMENT OF ENTOMOLOGY OF THE 
SYSTEMATIC REBPATION SET a: 
HISTORICAL. 
In 1857, A. Scheuten! discovered that the pustular spots of pear 
leaves were due to the work of mites, but in common with other 
workers of his day, notably Duges, he drew some erroneous conclu- 
sions from the specimens of mites representing several species, 
taken from the pear leaves, which he had under observation. The 
blister-mite was considered by him as a larva, a gamasid which was 
a vagrant guest or was feeding on the blister-mite was believed to 
be the adult, and a hypopus was regarded as an intermediate form. 
Scheuten designated the supposed adult as Typhlodromus pyri, by 
which the blister-mite was known in literature for many years. 
During the same year Pagenstecher? published some notes upon 
a number of mites, in which he merely mentions the leaf blister- 
mite and names it Phytoptus pyri, without giving a description. 
The mite was later studied by Nalepa? who in 1890 fully described 
and illustrated the external anatomy of it, which was the first 
adequate description of the species. 
*Scheuten, M. A. Troschel’s Archives, 1857, p. 104:—His descriptions of 
the supposed stages of the mite are briefly as follows: 
Larva.—A small white vermicle, 0.10-0.18 mill. in length and 0.025-0.040 
mill. in breadth. Body covered with transverse strize, which when highly 
magnified, prove to be firm, tubercular ribs, forming a strong shield. Animal 
with four short legs, inserted near rostrum. Body long, of uniform breadth 
with blunt termination, furnished with a pair of long undulated bristles. 
Between them are two smaller ones. Sides bear some bristles, which appear 
to support body in motion. Legs five-jointed, terminated by long nail or 
claw. Rostrum forms a truncated cone, containing sucking tube. 
Intermediate form.— Similar to a mite, but much smaller, with four pairs 
of legs, the anterior forming stumps, the posterior styliform, terminating in 
two bristles. 
Mite.— Form of mite oval, 0.30-0.34 mill. in length and 0.17-0.19 mill. in 
breadth. Mouth conical, acute and retractile. Palpi, five jointed, obtuse 
and strongly hairy, with apical joint set with bristles. Antennal jaws undis- 
tinguishable in living animals, but in glycerine preparations two clawlike 
jaws are seen. Palpi half-amalgamated with rostrum. Legs seven jointed, 
first pair distinctly longer than the rest, the two intermediate pairs shortest. 
Tarsal joint furnished with small funnel-shaped sucker which can be con- 
tracted, so as to appear like a simple claw on the first pair of legs, when 
employed in feeding. 
*>Verhandl. Naturhist. Med. Ver. Heidelberg, 1:48, 1857. 
* Sitzber. K. Akad. Wiss. [Vienna], 99:50, 1800. ale 
