138 THE EARLY STAGES OF TABANIDiE 



consequently incomplete; moreover, they are found frequently in 

 places where this Tabanus oviposits. But in many cases the egg 

 masses have been found to be much larger than the one described in 

 1905. In cases where the egg mass, fastened to a twig, reaches its 

 maximum of development, it is much more prolonged vertically 

 than the one figured in Lecaillon's first report, and it possesses a 

 second plane of symmetry which is horizontal and at right angles to 

 the principal plane of symmetry passing through the stem which 

 serves as support and through the anterior tip which presents the egg 

 mass. But only rarely will the egg mass be found entirely com- 

 pleted in this manner, and all the intermediate forms are found 

 between that described in the first publication and that described 

 later, with two planes of symmetry. 



Frequently the egg masses are found grouped together on the same 

 stem, numbering two, three, or four (Plate 2, Figs. 35 to 38). 



Finally, as stated also in Lecaillon's short note of 1906, two egg 

 masses are frequently not only contiguous but actually form the 

 continuation of each other (Plate 2, Fig. 3?>). Of these joint egg 

 masses Lecaillon is uncertain whether they are produced by one 

 female or by two different females. Probably the latter, inasmuch as 

 in the figures given their size is considerable ; also from our knowledge 

 of the egg-laying instinct of the female, it does not discern between 

 the eggs laid by itself and eggs laid by another; consequently it will 

 be likely to continue the process of oviposition started by another 

 female in case it, by chance, had alighted on a stem where already 

 other females were laying. As during the process of laying the 

 single egg is always placed beside another previously laid, one would 

 expect that in starting an egg mass, preference would be given to a 

 place where eggs are already present instead of places where only a 

 smooth surface is given. 



Sometimes the herbaceous stem which supports the egg mass is 

 very fine, and in these instances the latter surrounds it almost com- 

 pletely, even from behind, following the median line of the stem. 

 In other cases the egg mass is attached to the top of the spike of a 

 grass plant; in this instance it envelops only a small part of the 

 object, so that from behind the egg mass appears as of considerable 

 width. 



