368 GERALD F. HILL. 



Biology. 



This is one of the three predominant species of mound-building termites that are 

 found in the Townsville district, N. Queensland. It inhabits the same locahties as 

 H. peyplexus, sp. n., and the termitaria of the two species are often found in close 

 proxiimity, although those of the latter are rather more common, especially on hill- 

 sides. On the higher and stony localities many large colonies live entirely in under- 

 ground galleries, the extent and nature of which have not yet been investigated 

 sufficiently to determine whether they are connected with large masses of cells and 

 passages comparable with termitaria. This seems most probable, since it is known 

 that these colonies collect and store considerable quantities of food, and that eggs, 

 young larvae and the reproductive forms are not found in the galleries near the 

 surface, which serve apparently only for the accommodation of workers and soldiers, 

 and a few adolescents of these castes, and for the temporary storage of food material 

 during and just after harvesting operations. As all the normal castes are reared by 

 these colonies, it seems reasonable to assume that each is provided with an under- 

 ground system suitable for the location of the royal pair and their young and for the 

 storage of food. On the other hand, considerable excavating failed to disclose a 

 regular nest or " nursery " in the closely alhed species D. septcntrionalis, sp. n., in the 

 Northern Territory (Hill, 1915). In the case of D. septentrionalis, small foraging 

 parties of soldiers and workers are commonly found in the termitaria of Copioiermes 

 and Eutermes, but this is not the case with D. silvesirii. Access to the surface is 

 gained by means of numerous small oval openings, from 18 in. to 3 ft. apart, and 

 extending over an area of from 6 ft. to 12 ft. in diameter. These openings measure 

 about 3 mm. long by 6 mm., and except when actually in use, i.e., at harvesting or 

 " swarming " periods, are sealed with earthy matter, either level with the surface 

 or just below it, in either case rendering their detection very difficult. Similar surface 

 openings are found in the vicinity of termitaria, when these are constructed ; but 

 they appear to be used solely at harvest time — certainly not to provide a means of 

 exit for the winged forms at the time of swarming. The natural dispersal of the imagines 

 has not been observed, and it is not known whether the phenomenon occurs during 

 daylight or at night. A day or two before swarming takes place, slits are cut in the 

 walls of the termitarium, generally in several places near the outer margin and several 

 inches above ground level. These slits are sealed over by a projecting crust of moist 

 earthy matter, as in H. per plexus, sp. n., and remain thus until weather conditions 

 are favourable for the flight, after which they are cemented up flush with the general 

 surface of the walls. 



One of the most remarkable habits observed in this species, and also in D. septen- 

 trionalis, is that of gathering food supplies by day as well as by night. Froggatt 

 (1915) observes that travellers in the bush, who have gathered a mass of dried grass 

 upon which to make their temporary bed, have been aroused to find hordes of 

 termites (species not stated) cutting the material into lengths and removing it for 

 food. vSuch is by no means a rare experience in North Australia, and it occurs 

 during the day as well as at night, D. septentrionalis being the species concerned in 

 all cases which have come under my notice. In this district I have frequently seen 

 countless thousands of soldiers and workers of D. silvestrii issuing from several 

 holes in the surface and spreading out in irregular columns over an area of several 

 yards, each worker cutting off a length of grass (leaf or stem), a piece of eucalyptus 

 leaf or twig, or seizing a seed or small piece of bark and hurrj-ing back along the 

 column to one of the openings, at each of which there is a good deal of congestion, 

 but no sign of disorder or wasted effort. Throughout these operations the soldiers 

 are much in evidence, regulating the traffic, scouting on the outskirts of the working 

 parties, attacking marauding ants or any other insects or spiders they may encounter, 

 and generally taking a strenuous and important part in the proceedings. Their 

 behaviour is in marked contrast to that of their near allies the Hamitermes, and 



