22 AUSTRALIAISr SUGAR-CANE BEETLES AND THEIR ALLIES. 



The demonstration that the beetles do not stop at one set of eggs 

 was only made possible by a continued study of the reproductive organs 

 ■of the female, covering the whole period that they were on the wing. 

 Hundreds of specimens collected both from cane-leaves and from feeding- 

 trees were dissected day after day, noting the changes that took place 

 in the ovaries; and, finally, I sketched these structures (Plate 4) with the 

 camera lucida so as to get exact detail. 



A brief description of the female reproductive organs may be of 

 value here, especially to assist the reader in an understanding of the 

 following matter : — 



The two ovaries, each composed of six egg-tubes {Et) . are the 

 principal part of the female reproductive system. These, while the eggs 

 are undeveloped, lie in the ventral part of the abdomen and are closely 

 surrounded with air-tul^es, the latter not shown in this illustration. 

 Later, however, when the eggs are nearly ripe — two or more in each tube 

 (Plate 5. Fig. 8) — their mass practically fills the whole abdominal cavity. 

 Furthermore, in this drawing it will l)e noted that each egg-tube has a 

 series of ova (i.e. undeveloped eggs), and that these are of gradually 

 increasing size. These originate one after another from the long oval 

 body at the upper end, which is called the germarium. This structure 

 ■contains innumerable nuclei, each of which is capable of developing 

 into an egg if the insect lives long enough. Hence it will be seen that 

 the number of eggs that one of these l:)eetles may produce is only limited 

 by the time that it remains alive and active. And. finally, attached to 

 'Cach germarium is a terminal filament (T/), which attaches it to the 

 body-wall at the back, and thus acts as a support for these organs. The 

 six egg-tubes on each side open into an oviduct (0), and these again 

 unite to form a common duct, the vagina (Y), which opens to the 

 exterior. The vagina is expanded near its outlet into a large muscular 

 pouch, the bursa copulatrix (Be), which is a structure to accommodate 

 the intromittent organ of the male when mating. There is also a pro- 

 longed, tube-like structure, the spermatheca (S), opening from the 

 vagina; and a pair of dark-coloured, disc-shaped, cement glands (Cg). 

 The spermatheca, as its name indicates, is a receptacle for the sperm ; 

 the two glands form the sticky secretion which covers the eggs when 

 laid. 



The egg-tubes when the beetle first emerges are very small, usually 

 showing hardly more than a single tiny ovum in each (Plate 5, fig. 1). 

 Hence, as has been previously demonstrated, the beetles mvist feed for 

 approximately a fortnight after emergence before eggs are ready to lay. 

 Therefore, following upon this event, when I ]).egan to find great numbers 

 of the beetles Avith empty ovaries on the feeding-trees, I at once suspected 

 that they had laid and had returned to start all over again. That this 

 was a fact I was soon able to show, for I found that in a few instances a 

 •single ripe egg had been left behind in one of the oviducts after the set 

 had been deposited (Plate 6, fig. 1). In this sketch it will also be noticed 

 that the egg-tubes themselves were considerably distorted and wrinkled 

 innnediately after passing the eggs. This, however, is only natural, and 

 they become normal again very soon after laying, as will be seen in figs. 

 2, 3, and 4 of this same plate. 



How many sets the beetles normally lay we have so far not been 

 able to determine. This indeed is a difficult matter, for they do not 

 ■do well in confinement, usually dying soon after laying; and in the field, 

 •of course, it is impossible to determine the life of any individual. Hence 



