HEEy 1803) We SLPARCHMES ON INSEE ANATOMY. II5 
the Hippoboscide and in Braula and Nycteribia, elongated in the 
former and short in the latter group. Miiggenburg supports the gene- 
rally received view that the true proboscis is formed by the 
labrum, hypopharynx, and second pair of maxillze (labium). In the 
Hippoboscide this organ is long and flexible; in Braula and Nycteribia 
it is much shortened, and the formation of its ventral (labial) part by 
the fusion of a pair of jaws seems very clear (Fig. 2, mx?"). In the 
latter insects, also, the maxilla and their palps are connected at 
their bases; the mouth-parts have altogether a more typical aspect 
than in Diptera generally ; and it would seem that, in the course of 
the degradation consequent on their parasitic habit, the jaws of these 
insects have reverted in some degree towards a primitive form. 
Our knowledge of the ears of insects has lately received another 
contribution. Organs of hearing have not been recognised in many 
groups, but they have long been known in the jumping Orthoptera, 
the insects included under the popular terms grasshoppers and 
locusts. In the short-horned family of these insects, generally known 
asthe Acrididz, but henceforth in accordance with the law of priority 
to be styled Locustide,? the organs of hearing are paired, and situated 
on either side of the first abdominal segment. In the long-horned 
group, which is called Locustide by most entomologists, but which 
we must now learn to know as Phasgonuride, the ears are placed in 
the upper part of the tibial joints of the front pair of legs. The tibia 
is swollen just below the knee, and two slightly curved slits can be 
seen running longitudinally along the joint for a short distance 
(Figs. 4, 5). These are the openings into the outer auditory 
chambers. An account of these remarkable ears has lately been 
published by Von Adelung (3) who has studied their structure in the 
genera Phasgonuva (Locusta, auct.), Decticus, Thamnotrizon, and 
Meconema. 
The slits mentioned above open into chambers formed by the in- 
pushing of the integument of the Jeg. These chambers (Fig. 5) 
are thick-walled outwardly, but their inner walls are thin, and form 
the two oval tympana or drums, each of which is in contact with the 
wall of a trachea, or breathing-tube, the tracheal stem dividing in this 
region into two parallel branches, whose walls, however, remain in 
contact. The interior of these air-vessels functions as an internal 
auditory chamber. Along the outer wall of one of the air-vessels 
runs a ridge of tissue—the crista acustica—in which are arranged in 
linear series the cone-shaped endings of the nerve-fibres, each capped 
by a large cover-cell. These nerve-endings and their cover-cells 
become successively smaller from top to bottom of the series, which 
stretches parallel to and about as long as the longer axis of the drum. 
2 This change is less objectionable than many recent revolutions in nomen- 
clature, as the true locusts, which belong to this family, will henceforth be called 
Locustidz. Under the former arrangement they were excluded from the family 
named after them. 
12 
