DISSECTION OF LARVAE 423 



The alimentary tract of male flies, and of females which have only a 

 short ovipositor, is extracted by the same route, after incising the 

 membrane between the last and the penultimate segment, as in the case 

 of the Tabanidae. 



It is not possible to extract the salivary glands of Muscids through the 

 neck until their attachments, which consist of small but numerous 

 tracheal twigs passing between the glands and the gut, have been severed. 

 The following method is that usually employed. Hold the fly in the left 

 hand, between the ringer and thumb and with the dorsal surface upper- 

 most. Take a sharp knife or a razor, and make a longitudinal in- 

 cision in the middle line of the thorax and abdomen, carrying it as far 

 down as possible, but making it just deep enough to pass through the 

 chitin without injuring the soft structures. Then lay the fly in a drop 

 of saline, and tear the two sides of the incision apart, completing it at 

 the junction of the thorax and abdomen with a few cuts from a sharp 

 needle. The coils of gut and gland come into view on the removal 

 of the fat body, and there is usually no difficulty in separating them. 

 The muscles of the thorax should be separated in the middle line, 

 and the anterior and dorsal boundary of the neck broken through. 

 The fly is now turned over on its side, and one needle thrust through the 

 middle of the head. A cut is made with a sharp needle to sever the 

 pharynx from its attachment to the head, and the needle then passed 

 through the basal part of the proboscis (the bulb in the Stomoxydinae). 

 The long glands can now be drawn out of the body while still attached to 

 the hypopharynx. 



The dissection of pupiparous flies, especially when in an advanced 

 stage of gestation, is very tedious and difficult, owing mainly to the 

 leathery nature of the integument and the very rich 

 tracheal supply which goes to the uterus. The abdo- Di88ec " on of Hi PP- 



DOSCil 



men, in the case of Hippobosca, for instance, is best 

 opened by cutting around the lateral borders with a pair of fine scissors, 

 until the whole of the dorsal wall can be raised as a flap. The uterus 

 should next be isolated by cutting through all its tracheae, and then 

 removed by cutting across its lowest portion with scissors. It is not pos- 

 sible, or at least extremely difficult, to get out the alimentary tract until 

 the uterus and its tracheae have been got rid of. 



The dissection of larvae is, as a rule, easy enough, the whole of the 

 alimentary tract coming out by the posterior route ; it is well to detach 



the last segment and make a few pulls to bring out the 



. , . . . Dissection of larvae 



posterior part of the alimentary tract before cutting off 



