BOTH THE SEXES IN DIPTEEA. 359 



of the MiiscidPB, calyptrate and acalyptmte. In Stratiomijs, Empis, DoUchopus, and 

 Si/rphus it is found to be longer and more capable of extension. In some of the 

 Muscidae it is at its greatest proportionate length in its membranous form. In the 

 acalyptrate Ortalidre, Trypetidse, and Loncbyeidse it is equally long, but hard and horny 

 and capable of depositing the eggs under the cuticle of leaves. In the minute Phito- 

 myzidae it is shorter, but still a horny, minutely-aculeated organ. 



" Heceptacnlar — An examination of a prepared slide of a female shows from one to 

 three, rarely four, chitinous sacs, mostly of an oval or pyriform shape, with more or less 

 short ducts leading from one end; these are the receptacula seminis or spermathecas. 

 In Musca domestica they are situated at the end of the long fold of the ovipositor into 

 which the ductus ejaculatorius of the male discharges ; they absorb the spermatozoa, 

 and again eject them when the ova in their passage down the oviduct compress the 

 receptacula. 



In the preparations they are found either in the abdomen or in the extruded 

 ovipositor, and possibly, on a cursory examination, might be mistaken for eggs. 



" Glue-glands." — Excretory glands will also be found in some ovipositors, sometimes 

 called " glue-glands." The eggs adhere to each other or to their resting-places by means 

 of the fluid from these glands, with which they are anointed in their passage through 

 the ovipositor. 



Types in the Mnscidce. — In the Muscidae there are several types of this organ : — 



(1) That in Musca domestica is long and telescopic, with three joints, and has on the 

 anal segment two feeling-organs or valves, a semi-ovoid and two triangular plates (these 

 latter probably representing the eighth segment of the abdomen) and two gther segments 

 supported by ten chitinous rods (a pair of these rods being fused at the base), and a 

 number of transverse setose j)lates (PI. 29. fig. 107). 



(2) In Lncilia it is also long and telescopic, but has plates instead of rods, and on 

 the dorsal plate of the third segment, the anal segment counting as " one," are two 

 pairs of spiracles close to each other. 



(3) In Calliphora it is much shorter, but has plates and paired spiracles on the same 

 segment as in Lnoilia. 



(1) In FoUetes lardaria (Fabr.) it is again long and telescopic as in M. domestica, 

 has the usual valves on the anal segment, but neither rods nor plates, the segments 

 being marked by small transverse bristly bands of chitin, and without spiracles on the 

 third segment. 



(5) In Hydrotcca dentipes, Fabr., it is long and telescopic, has plates which seem to 

 be thickening into rods, and two pairs of spiracles on the third segment, as in Calliphora 

 and Lncilia. 



(6) The very short ovipositor that is found in Scatophaga and Authomi/za (PI. 28. 

 tigs. 90, 100 ; PI. 30. fig. 131). 



(7) The horny, extrusive ovipositor that is found in those families already alluded to 

 (the Ortalidse, Trypetidae, Lonchaeidaj, and Phitomyzidic) (PI. 28. fig. 95). 



The Spiracles. — In com])aring the ovipositor in different families, and homologiziug 

 it with the male armature, the presence or absence of spiracles on the segments might 



