4 Introduclion. 



R. H. Stainin and Axel Petersen in Silkeborg, and M. C. Godskesen 

 has presented me with his coUection of Diptera coUected in the environs 

 of Hillerod. I shall especially mention Mr. Schlick's collection which. 

 besides being rather large, has the advaiitage thai it contents a great 

 many brei'd flies togelher with their larvæ and pupæ. Mr. Schlick has 

 also for many years breed Hymenoptera, and among these many species 

 from Diptera; the most of what I say in my work about Hymenoptera 

 parasitic on flies is due to Mr. Schlick. — To all the above named 

 gentlemen I beg here to tender my sincerest thanks. 



The tenainology I use in my work is chiefly the common one. 

 On the head the part at the top between the eyes is the vertex; it 

 bears the ocolli wlion these are not absent. Below the vertex down 

 to the antennæ, or in cyclorrhaphous flies, to the lunula, lies the front ; 

 when the eyes are touching, the vertex above and the front below 

 both get a triangular shape and may then be ternied vertical and 

 frontal triangles. Below the antennæ down to the mouth-edge or near 

 to it lies the epistonia; to each side of it, between it and the inner 

 eye-margins are the cheeks, they are sometimes well separated by a 

 furrow or a keel from the epistoma, especially in flies with a frontal 

 bladder, but they may also be more or less confluent with the epistoma. 

 Below the eyes, to each side of the oral aperture. lie the yowls which 

 may be more or less produced below the eyes. or they may be 

 horizontal and not at all extending below the eyes; they lie between 

 the oral aperture and the lower eye-margin ; sometimes they may be 

 very narrow, only forming a narrow margin between the eye and the 

 mouth opening, or the eyes may reach so near to the aperture tliat there 

 are almost no cheeks. The front side of the head below the antennæ is 

 sometimes spoken of as the face, this thus including the epistoma, the 

 cheeks and sometimes also part of the yowls. 



The mouth parts consist of the same parts as in hisecta mordentia, 

 viz. mandibles, maxillæ and labium; mandibles and maxillæ. when 

 present, are generally more or less elongated, somewhat lancet- or 

 bristle-shaped ; the mandibles are only present in the females of some 

 orthorrhaphous flies, and the maxillæ are often short. rudimentary or 

 quite wauting, as in most cyclorrhaphous flies; but maxillary palpi 

 are almost always present consisting of one or more joints. The labium 

 when normally developed is more or less semitubiilar. enclosing the 

 other parts and terminating with a jiair of lips, the labella, which may 

 be very diflferent in (orm and development, broad and somewhat 

 swoUen or long and narrow or of other forms, and sometimes very 

 small. The labium itself may be of difl'erent lengths, from very short 



