DR. J. BRAXTON HICKS ON UNDESCRIBED SENSORY ORGANS IN INSECTS. 141 
sure about ttoo iuch. They are found on the same parts in Acheta and Blatta, of th< 
form of those of the Scorpion-fly, as below. 
In the Scorpion-fly (Panorpa communis) they are found in a group of ten to twelve on 
each side of the trochanter (PL XVIII. fig. I, 1) each one is oval ; and has on one side 
a ridge running in the direction of the longest diameter (fig. I, 2 c). They arc also 
found in Libellula in the same parts. 
In the genus Gerris (Hemiptera) the organs are found in two groups on the trochanter, 
about four in each group, and their shape is different from those hitherto described, being 
oval, with a point at each end and a papilla in the centre (PL XVIII. fig. K, a). The 
same organs are found in the Water- Scorpion {Nepa cinerea). 
In the genus Vespa they are found in a group on both the trochanter and femur, near 
the joint, and a few scattered over the trochanter. I have represented those of Vespa 
Crabro at PL XVIII. fig. L, 1 ; they are circular at the surface. The tubes leading to 
the surface are curved; the nerve proceeding to them can be plainly seen, as is shown 
at fig. L, 2. 
In the Hive-Bee these organs are not so numerous, but are situated in the same part. 
In Formica rufa, or the Wood-Ant (PL XVIII. fig. M, 1), the organs are very numerous, 
and exist both on the trochanter and femur (fig. M, 1, a a). The nerve can be seen passing 
to the different groups. On the femoral end also of the tibia are to be found a few small 
groups, to which the nerve can be traced (fig. M, 2). Their diameter is about 3^ inch 
In the various Tenthredines the same organs are to be seen (PL XVII L fig. N, 1), 
larger than the foregoing, and their form, which is shown at fig. N, 2, is somewhat conical. 
They exist in two groups-one small, on the coxa ; and the other larger, on the trochanter. 
The organs on Grylla viridissima are represented at PL XVIII. fig. 0, 1. They exist 
on the first and second legs, but not on the third leg ; they are in three groups, two on 
the trochanter and one on the femur. 
At this place I may mention that I have examined the dilatation on the fore leg o 
Gryllus and Zocusta, considered by Siebold* as the " organ of hearing," and I have arrived 
at the same conclusion as M.Lespes in the ■ Ann. des Sci. Sat.' 1858, namely, tha t there 
is no special nerve proceeding to the dilatation, but that within it there is a swelling ot 
the trachea which principally occupies the space, and that the nerve passes deeper down 
behind this tracheal swelling, being continued through the joint to the extremity of he 
leg. I have bleached the integuments, and have been able to see quite through the leg 
by adjusting the focus suitably. , . ,., 
The next portions of the Insect to which I wish to direct attention are ^V^Jbrtb 
maxillary and labial. If we examine, with J to 1-inch objective, the palpus of th, 
common Blow-fly {Mmca vomitoria), it will be seen to be studded wi h a number of small 
transparent dots over more than half its surface, more thickly towards j the apex 
(PL XVIII. fig. P, 1). Their true nature it is difficult to tell, but i is probablj some, 
thing similar to that which I shall describe in Vespa Crabro. I have town them 
enlarged (fig. P, 2), with the minute hair-lite cuticular projections between them, tneir 
diameter in this Ply is 5 o'a tf iuch. 
Wiegm 
