102 M.H. Rathke on the Respiratory Process in Insects. 
B. Grubs and Caterpillars, 
The traches of these larvee were examined immediately after 
they had been opened down the back, both with the simple lens 
and with the microscope, but no contractions could be observed 
in them even when irritated mechanically or with alcohol. 
§ 25. The larvee of Vespa crabro and V. vulgaris, both when 
within their cells and after removal therefrom, frequently shorten 
and elongate their bodies, at the same time curving them laterally 
either to the right or left. In the latter movement the convex 
half of the body also becomes smoother, and the concave half 
thicker than before, a portion of the fat and other structures 
contained in the body being pressed from the former into the 
latter. 
- The skin between each two contiguous segments is somewhat 
thinner and softer than in the segments themselves, and at the 
point where the upper and lower halves of each segment come 
together the skin is likewise thinner and softer, and forms a 
projecting fold. From the entire anterior margin of each seg- 
ment, except the two soft spaces on the right and left sides and 
the spaces where the dorsal vessel and ventral ganglionic cord 
lie, there runs a great number of nearly straight and pretty thick 
muscular bundles, forming two superior and two inferior layers ; 
these pass nearly to the corresponding margin of the preceding 
segment, and not only shorten the body, but also, by acting on 
one side, curve it to one side. Besides these, on each side, partly 
from the upper end of the lower half of each abdominal segment. 
close to the soft skin, and partly from this soft skin itself, two 
delicate and closely approximated muscular bundles pass inwards 
and downwards to the lower half of the preceding segment, 
attaching themselves partly to the anterior margin of this in the 
vicinity of the ganglionic chain, and partly running further in- 
wards and forwards to apply themselves to the upper surface 
of the straight muscles of the next anterior segment. These 
latter muscles may flatten the body, and appear to be antago- 
nistie in the two halves of the body; so that when those of the 
left side contract, those of the right side are relaxed, and vice 
versd. The straight longitudinal muscles are likewise antago- 
nistic in the two sides of the body. When the entire body con- 
tracts in the direction of its length, during which the segments 
themselves, consisting only of a soft skin, are somewhat short- 
ened, it is extended again, after the relaxation of the muscles, 
only by the elasticity of the eutis and of the contents of the 
cavity. 
‘ All the trachez are ramose, and all the stems of each 
side of the body are united, as in the perfect Wasps, by a com=: 
