32 
MR. LUBBOCK ON THE DISTRIBUTION 
inferred that tlieir ultimate structure also varies less than that of other parts. The 
ganglia are always well and often very richly supplied with tracheae, differing in this 
respect from the commissures and nerves, which in many insects (as mentioned helow) 
are entirely free from them. The tubules, excepting sometimes those which are distributed 
to the surface, are straight or gently curved, but not waved. They generally rise singly 
from the branchlets, as in PL I. fig. 1 ; but sometimes, even in the same insect, we find 
tufts, as in PI. I. fig. 3. 
The abdominal ganglia in JBombus terrestris and B. lapidarius, are covered over with 
a network of tracheae. The meshes vary much in size, from 3^0 i nc h i n length and y^ 
inch in breadth to less than ^oth of that size. The tracheae forming the network are 
of considerable breadth, averaging perhaps ^ inch. The short commissure between 
the posterior and penultimate ganglia has as rich a network of air-vessels as the ganglia 
themselves. 
These latter are penetrated by numerous branches which end in tufts (PI. I. fig. 3) 
of from five, or even six, down to two or three. The tubules branch two or three times, 
and resemble a fishing-rod in their general proportions and curvature, running in a gentle 
sweep often for T J^ inch, with a thickness at the base of only 15 ^ 00 inch. 
The ganglionic trachese of Fanorpa, Libellula, Carabus, and Aphropliora are like those 
of Bombm ; and so are the tracheal tubules of Vespa, Tenthredo, Athalia spinarum, 
Ichneumon (probably) extensorius, Ophion, Chrysopa, Tipula, Campcea margaritaria, 
Callwiorpha jacobtece, Fterophorus, and the larva of Euplexia lucipara; but I am not 
sure whether the branches end in tufts. In none of them is there a network enclosing 
the ganglia, as in JBombus, 
In the larva of Lampyris, Amphimalla, Acheta (both larva and imago), Locusta, and 
Gryllus, the tubules are larger and longer, but otherwise very similar. The branches, 
however, do not end in tufts. 
In Forficula the trachese resemble those of Acheta, but are smaller. 
In Necrophorm humator, N. vespillo, Scarabceus, and Musca, in Hipparchia Jcmira, 
Fieris napi, Noctua gamma, the larva of Lasiocampa rubi, of Mamestra brassier, of 
Gonepteryx rhamni ; the tracheae sometimes end like the preceding, and sometimes in 
tufts, a large branchlet ceasing suddenly and giving off from four to seven or more tubules. 
These latter divide and re-divide again, sometimes breaking into little secondary tufts. 
In the larva of Musca the mode of branching is quite unlike that of the imago, being 
simple and not in tufts. 
In Hydrous piceus the tracheae are in tufts ; but the tubules rising from them are 
nearly of uniform size, so that there are no secondary tufts. 
In Bristalis the tracheae of the ganglia break into tufts like those prevalent throughout 
the body. Upon the surface they are waved and resemble those of the commissures ; but 
in the interior of the ganglion they seem to be straighter. 
In Fentatoma large wide tracheae go to the ganglia, and give off short thick branches. 
These again give off still shorter branchlets, which end in tufts consisting each of a few 
straight tubules (PI. I. fig. 5). 
