50 DIPTERA OF AUSTRALIA, 



was undoubtedly thread-work, but that the cocoon became de- 

 posited around the insect in crystalline form, without the larva 

 betraying the slightest movement. The cocoon is ready after a 

 few days, and even then under a high magnifying power no 

 proper thread can be noticed. It is doubtful if the larvte of the 

 Cecidomyidte undergo moultings. I believe that the length of 

 time they remain in the larval form depends very much on the 

 weather. They may be kept for months in that state in a dark 

 box, but will emerge if restored to ordinary conditions. All are 

 very liable to the attacks of parasitic Hymenoptera belonging to 

 the family Proctotrupidje. 



About thirty years ago, Dr. Wagner, then Professor of Zoology 

 in the University of Kasan, observed an asexual reproduction in 

 the larvae of a certain Cecidomyid. His observations were at first 

 regarded as apparently "almost incrediVjle," but were afterwards 

 confirmed by the researches of Meinert, Pagenstecher, Loew, and 

 other authors ; and, according to their investigations, this "alter- 

 nation of generation" (douVjtless frequently occurring throughout 

 the Cecidomyidse), greatly resembles the mode of reproduction 

 long before known to prevail in the Aphides. 



Unfortunately, I have not yet been able to observe these germs 

 in Cecidomyian larvje, and must, for the present, refer those who 

 desire to know more about this remarkable phenomenon, to the 

 numerous papers which have been published from time to time, 

 on this subject. 



III. Pupa, 



The pupa is smooth or minutely granulate (the dorsal abdominal 

 segments often spined) and beai-s a considerable resemblance to 

 the perfect insect, the eyes, head, thorax, antennje, and feet being 

 distinctly determinable, even to the joints of the two latter. The 

 bases of the antennae are frequently produced in points ; these are 

 long, hornlike, and close together, or short and wide apart. Two 

 pairs of bristle-like processes appear in most pupse, one on the 

 head near the hornlike points, and the second pair on the thorax, 



