SCENT ORGANS IN TRICHOPTERA. 467 
two “ windows” of thin delicate chitin divided by a median bar 
of thicker chitin running dorso-ventrally. The segment itself is 
almost immobile, but its enlarged size allows for the presence 
of muscles by which the long whip-like remainder of the antenna 
can be moved. 
Text-figure 9. 
Sericostoma personatum, 3b. 
Sagittal section of the head, with the palpus of the first maxilla and the first 
joint of the antenna seen from the inside (diagrammatic). 27. 
The shape of the tentorium appears to indicate limited anten- 
nary movements, as the two columnar endosternites or supporting 
pillars, which run from the cross-bar at the occipital foramen 
across the inside of the head to the clypeus, are simple, without 
wings or lateral expansions from which, when present in 
Phryganea and other genera, arise numerous powerful muscles 
to the antenne. In the female of S. personatwm, where the 
antenne have much smaller basal segments, the tentorium is, 
however, similar to the tentorium of the male in the absence 
of its wings. 
The head of the female is more or less normal. The maxillary 
palpi are fairly long 5-jointed appendages; the chitin of the 
clypeus is dark brown in colour and of equal thickness to that 
of the rest of the head. The mandibles are aiso much longer, 
Proc. Zoou. Soc.—1914, No. XX XI. 3l 
