TIE INSECTA. $ 338. 
The mouth of the larvae of the Myrmeleonidae, Hemerobidae, and 
Dytiscidae, is of a very peculiar construction. There is no oral orifice, 
properly speaking, and the maxillae and mandibles are wholly unfit for 
mastication, the latter being changed into two curved hooks, hollow and 
with a narrow fissure at their extremity. These larvae bury these hooks 
in the insects they have seized, and through the cavity of these organs, which 
communicates at its base with the oesophagus, suck the blood.“ 
A considerable number of the Insecta take no food during their perfect 
state, the object of their existence being only to accomplish the act of repro- 
duction. Their jaws are often very rudimentary and are fit neither for suck- 
ing nor for masticating.“® In somé cases, indeed, not only are these organs. 
wanting, but the oral orifice is closed as with all inactive pupae. 
§ 338. 
The Digestive Canal of Insecta .and their larvae, is more or less long, 
sometimes extending from the mouth directly to the anus upon the median 
line; sometimes forming in the abdomen loops and convolutions. It is 
retained in place not by a mesentery, but by numerous fine tracheae, 
which envelop its entire extent. It is always wholly invested by a homo- 
geneous peritoneal envelépe under which lies a muscular tunic, composed. 
of longitudinal and circular fibres, which are especially developed about the 
mouth and anus. Internally, it is lined throughout by an epithelium which 
is extremely thin at the middle portion of this canal, but very solid and 
composed of chitine at its two extremities. In the middle portion just 
raentioned, there is a layer of aggregated cells, evidently of a glandular 
nature, between the epithelium and the muscular tunic. 
The different parts .of this canal in the Insecta may be properly distin- 
guished in the following manner. The first portion is the Oesophagus, 
muscular, occupying the three thoracic segments and often dilated at its 
posterior part into a crop (Ingluvies) and muscular gizzard (Proventriculus). 
Sometimes there is appended to the cesophagus a sucking stomach consist- 
ing of a more or less pedunculated, thin-walled vesicle, which is multiplicated 
on itself when empty. 
The second portion consists of a stomach (Ventriculus), in which the 
chyle is formed, and which is continuous at the point of insertion of the 
Malpighian vessels, with the third portion of the digestive canal. This 
third portion commences by a small and usually short JZewm, which is fol- 
lowed by a Colon, larger and of variable length. This last often has a 
Caecum at its anterior extremity and terminates posteriorly in a short mus- 
cular Rectum.) 
18 See Roesel, Insektenbelust. III. Taf. XVII. 
XVIII. (Myrmeleon), II. Insect. aquit. classis I. 
Yaf. I-III. (Dytiscus) ; Ratzeburg, Forstinsekt. 
III. Taf. XVI. (Hemerobius). With the larva of 
Dytiscus, the body of the maxillae is wholly abor- 
tive, but always provided with palpi. With those 
of Hemerobius, the maxillae are small, deficient in 
‘palpi, and play in a groove on the concave side of 
the mandibles ; finally, with those of Myrmeleon, 
these organs are wholly enclosed in the cavity of 
‘the mandibles. 
19The maxillae are rudimentary and very soft 
with the Ephemeridae, and Phryganidae, in the 
last stages of their development. The very short 
proboscis of many Bombycidae and Hepiolidae, ap- 
pears equally unfit to receive food. Finally, the two 
small, intercrucial maxillae of the males of the 
Strepsiptera, are wholly inadequate for the func- 
tions of masticatory organs. 
20 Movable oral organs and’ an oral orifice are 
wanting with many Oestridae, and Henopidae, as 
well as with the male Coccidae. 
1 The functions of these different portions of the 
digestive canal do not always correspond to those 
ofthose parts having the same names with Verte- 
brata. Burmeister (Zur Naturgesch. d. Calandra 
p- 9) is certainly correct in saying that the stomach 
is the chylopoietic part, thus combining the fuue- 
