62 BULLETIN 66, UNITED STATES NATIONAL MUSEUM. 



TRACHEAL SYSTEM. 



So far as known the Strepsiptera have one pair of spiracles located 

 in the posterior part of the metathorax, on its dorsal surface, in young 

 male larvse, but moving forward with increasing age. In Acro- 

 scliismus the spiracles seem to be located in the mesothorax on the 

 pleurae (see Mesostigmatal lobe, p. 65.) In male pupse they are 

 arranged on a separate elevation (Nassonow, 1892 e,pl. 1, fig. 27 b). In 

 the females the spiracles are often very prominent and under a micro- 

 scope the direction of the tracheae can be traced. The stigmatal 

 trachea is short, being divided in the first abdominal segment into 

 three main tubes. The first tube to branch off is the cephalothoracic, 

 which passes forward and unites with that on the other side under 

 the intestinal canal and behind the brain. The side branches of 

 this tube supply the legs, wings, thoracic muscles, anterior intestine, 

 and thoracic ganglion. The connecting tube supplies the muscles 

 of the head and the brain. 



The abdominal main tubes arise from the main stigmatal trachea 

 and pass backward, one dorsal and the other ventral. The first 

 abdominal segment is supplied by tubes arising at the separation of 

 these two main trunks. The two tubes supply the abdominal 

 muscles, and all organs lying in the second to eighth segments. The 

 two tubes are reunited between the seventh and eighth. The ninth 

 and tenth segments are supplied by two tubes arising at the union 

 of the main tubes (Nassonow, 1892 e, pi. 2, fig. 16; Nassonow, 

 1892 c, pi. 1, fig. 14). 



REPRODUCTIVE SYSTEM. 



In the larvae the sexual organs are practically alike in both sexes, 

 consisting of longitudinal cylinders lying in the abdominal segments 

 along the sides of the intestinal canal nearer to the ventral surface 

 of the body. From the apices of these glands arise mesodermic 

 bands directed to the lower side of the outer covering of the ninth 

 abdominal segment (Nassonow, 1892 e, pi. 2, figs. 2, 4, 16). 



In the male this mesodermic band becomes hollow and funnel 

 shaped at its base, although cut off from the gland by a layer of cells. 

 The two bands approach, and form a pear-shaped blind sac which 

 later finds an exit through the ninth segment. During the pupal 

 stage the partition between the glands and ducts is resorbed. The 

 development continues by reducing the length of the ducts until, in 

 the adult, the vesicles empty almost directly into the ductus ejacula- 

 torius (Nassonow, 1892 e, pi. 2, figs. 8, 9, 10; Nassonow, 1892 c, 

 pi. 2, fig. 11). 



In the female the rudimentary glands become broken up and the 

 egg masses lie throughout the body cavity. Median invaginations 

 of the ventral surface occur in the female beneath the cuticle of the 



