310 CLASS VIII. 
consisting of five joints. The last joint has two claws and two or 
three plane elevations or cushions (see above, p. 252). 
The digestive organs of Diptera consist of a wide bent stomach 
of moderate length, a small intestine, and an oval oblong large 
intestine. The salivary vessels vary in the different genera of this 
order. The cesophagus has a dilatation (éngluvies, crop, see above, 
p- 254); it is a bladder of various form, either simple, or pro- 
longed into two or more divisions, and communicating with the 
cesophagus by a long narrow tube (often with its lowest part close 
above the stomach). In larve the tube is shorter and inserted into 
the cesophagus higher up. In by far the greater number of Diptera 
this bladder is present ', in the family of the Pupipare it is wanting 
(comp. Rampour, Abhandlung. iib. die Verdauungswerkzeuge d. Ins. 
Tab. XIX.—xx1, and pp. 170—185). Treviranus named this organ, 
which is also found in the Hymenoptera and Lepidoptera, sucking- 
bladder ; he attributed to it a power of expanding, in consequence 
of which the air in the cesophagus is rarified, whilst, to fill this 
partial vacuum, the fluid in which the extremity of the sucker is 
planted ascends as if pumped up, (Verm. Schr. u. s. 110). The 
Hemiptera and the Pulicide do not possess this bag ; on the other 
hand, such a crop is present in the Orthoptera, which do not suck, 
and according to Leon Durour in @demera amongst the Coleoptera 
(Ann. des Se. nat. m1. 1824, p. 484, Pl. 30, fig. 7). The name of 
Jood-bag, which was given by Rampour to this part in Diptera, is 
therefore more appropriate than that of sucking-bladder. When 
flies that have long fasted suck their full of milk, according to the 
investigations of Hunrrr, milk penetrates into this bladder. By 
pressure of the abdomen, and apparently also by contraction of the 
muscular walls of the bladder itself, the food is afterwards brought 
back from this diverticulum or reservoir of nutriment to the sto- 
1 According to the anatomical investigations of SCHR@DER VAN DER KOLK it seems 
to be wanting in the larva of @strus; but at the same point where ordinarily the 
tube from the food-bag [the name given by RAmpouR to the sac] is inserted into the 
cesophagus, two tortuous canals are seen, which divide at their other extremity into 
two branches, which are distributed to the adipose body. Mémoire sur ?Anatomie 
et la Physiologis du Gastrus equi. Amsterdam, 1845, pp. 29, 30. Pl. 111. fig. 1, b, 8, s. 
Ramvour has figured four such appendages above and near the stomach in the larva 
of Musca vomitoria, which would seem at their other extremity to be implanted into the 
salivary vessels, and in the perfect insect to disappear. Tab. xx. fig. 1. M, M, M, M. 
Do these vessels form, perhaps, a second apparatus for secreting saliva ? 
