FAMILY TABANIDAE: BREEDING HABITS 297 



instance, lay their eggs on the leaves of water weeds, and on blades of 

 grass. Tabanns kingi, Aust., lays its eggs on rocks over deep pools. 



In Madras, Tabanns albimedius, Walk., oviposits in a variety of situ- 

 ations, but most frequently on the leaves of some plant overhanging deep 

 water. Its egg masses have also been found on small rocks in the bed 

 of a stream, and on pieces of string hanging over house drains ; on 

 one occasion a mass was found on a Papaya tree, at the foot of' w r hich 

 water was occasionally allowed to flow. Tabanns speciosus, Ricardo, 

 always lays its eggs on the leaves of water lilies growing in deep water. 

 Tabanns striatus, Fabr., oviposits as a general rule on blades of grass, 

 pieces of stick, etc., at the edge of a river, stream or pond ; Tabanns 

 hilaris, Walk., has the same habits. Chrysops dispar, Fabr., Tabanus 

 ditaeniatus, Macq., Tabanus bicaUosus, Ricardo, Tabanns virgo, W r ied., 

 and two undetermined species of Haematopota, all of which are small 

 tabanids, invariably lay their eggs on blades of grass just at the edge of a 

 shallow stream, or on the leaves of the lotus plant at the edges of small 

 ponds, but never over deep water. 



The position selected by any one of these flies to deposit their eggs is 

 not a chance one. The larvae of the larger tabanids, such as albimedius, 

 striatus, and speciosus, are powerful swimmers and have air sacs con- 

 nected with their tracheal tubes, so that they can float or sink at will. The 

 larvae of the smaller species in Madras are devoid of these air sacs, so 

 that if they fall into deep water they die. It is important to recognize 

 this in breeding experiments and to place them in trays with only a little 

 water. 



The number of eggs laid by the different species is also of interest. 

 T. albimedius and T. speciosus lay between 500 and 600 eggs, while the 

 smaller species lay about 300. When one of the larger species is 

 about to oviposit it alights on the leaf or blade of grass with its head 

 downwards ; it then thrusts the tip of its abdomen forwards under its 

 thorax, and deposits an egg, which adheres to the leaf owing to the 

 sticky substance which accompanies it. The abdomen is then returned 

 to its original position, and as soon as the next egg is ready to be 

 laid, is again flexed, and the second egg is placed at one or other 

 side of the first. In this way three or four eggs are laid on one side of 

 the first and three or four on the other. The mass at this stage has the 

 shape of a V. The fly now moves forwards, and, raising the end of her 

 abdomen to one arm of the V, places a number of eggs down the side 

 until the apex is reached ; she then changes over to the other side and 

 deposits eggs all down that arm up to the apex. In the end a raised 

 38 



