74 INSECTS AFFECTING DOMESTIC ANIMALS. 
Usually a y-shaped, bent chitinous plate is to be seen, whose open side looks up- 
ward; from the side it has the shape of a sitting butterfly whose large upper wing 
reaches far back and has the smaller, narrow under wing under it. Since the wings 
of the two sides are grown together firmly underneath, the whole pharyngeal frame- 
work appears like a flying insect, when the wings are bent apart from above, and 
with the base in a plane. The part lying more or less in front, which is to be found 
in the middle between the wings, and which really radiates out into these, or is united 
with them like a ligament, is what Schroeder van der Kolk calls the tongue bone. 
In the pharyngeal framework, therefore, there can be recognized a body (Schroeder’s 
tongue bone) and four wing-like processes, which often, again, consist of several parts. 
The body is connected with the wings posteriorly. It is always bent in a U-shape, 
and so that the open end looks upward, i. e., if other soft parts of its vicinity which 
also close this are disregarded (p.37). Bent flat, it shows a more or less distinctly 
H-shaped chitinous plate, with very broad side parts, which—in full-grown larve— 
become confluent behind into a simple, broad plate, and only Jeave an oval hole in 
front of them for the passage of the discharge duct of the salivary glands, but pos- 
teriorly bear the four wing-shaped processes (two large upper, or in the outspread 
plate outer ones, and two smaller slenderer inferior or inner). On the anterior end 
of the body, in many genera, oral hooks are jointed to the short anterior side parts. 
In the anterior curved excavation of this lies in the membranous expansion a small 
corneous chitinous plate which is pierced like a sieve and whose nature has not yet 
been more closely investigated. It seems to me as if this plate lay at the outlet of 
the salivary ducts. It is especially distinct in Cephenomyia larve. It is wanting 
in several others. 
In young larvee, the pharyngeal framework consists only of two chitinous rods, 
which are united in front by a chitinous band. These chitinous rods radiate out 
behind in little wings. A (similar) pharyngeal framework occurs in all other museid 
larvie, and corresponds in the perfect insect to the chitinous frame of the proboscis. 
I have repeatedly convinced myself that such is really the case, since I have opened 
the coarctate pup:e of Cephenomyia and Gastrophilus before the emergence of the 
flies. Since, in these genera, as we will see later, the nymph is tightly inclosed by 
the puparium, it can be noticed how the already freed pharyngeal framework, which 
remains attached to the puparium, rests in the mouth fissure of the nymph, and is 
drawn out of it as soon as the nymph is taken away or the lower lid is lifted off. 
It is also easy to form an idea that the pharyngeal framework, together with its 
internal parts, corresponds to the proboscis of the fly if it is observed how other 
muscid or syrphid larve while alive project and withdraw this exactly as the fly 
does its proboscis. 
In Hypoderma, the mouth parts undergo a retrograde metamorphosis from the 
second stage (after the first molt); the oral hooks disappear, and therewith all the 
external mouth parts, but the internal pharyngeal framework remains. 
(4) The estrid laryze show antenne (at least rudimentary ones) above the mouth 
parts; these have the appearance of corneous or usually membranous knobs, and in 
the latter case are provided with one or two ocelli-like points. Subulate, many- 
jointed antenn, such as occur in many muscid larve, are never found. 
(5) All possess an anus, which lies on the last ring, under the stigmata] plates, 
and is very small. 
(6) They molt twice while they are parasitic. I have observed most closely the 
molting in Hypoderma larvie of the second stage. In H. diana, the passage from 
this stage (p. 38) to the last one takes place about the beginning of February. If 
in a cutaneous muscle which is richly larded with such larve the capsules of 
those larvee whose hinder stigmatal plates have the shape of the third stage, but 
are still clear yellowish-brown, are carefully slit open, the skin characteristic of 
the preceding stage, with the many little thorns heaped in groups, will be found 
either still partly attached to the front end of the larva or entirely dependent from 
the cephalic end or folded together along the dorsal side. The process of molting 
