360 Transactions of the Society. 



at its junction with the pronotum. On dissection this aperture is 

 seen to consist of an invagination of the cuticle ending in a point 

 inside the thoracic cavity. The hole in a typical specimen is 

 situated • 43 mm. from the anterior border of the mesonotum, with 

 which it is connected by a shallow groove, rather narrower than 

 tlie diameter of the hole itself. The actual aperture measures 

 0-21 mm. long by 0'12 mm. wide. Seen from the interior of the 

 mesonotum, the funnel-shaped invagination measures 0-68 mm. 

 from the border of the segment, and • 32 mm. from the opposite 

 edge of the hole to the point. The point itself is generally rounded. 

 Several other specimens were examined and measured, the aperture 



Fig. 4. — Worm in situ in abdomen of female ant. 



and length of the point varying very slightly in different indi- 

 viduals according to their size. 



This condition may be, and probably is, connected in some way 

 with the parasitized state of the ant, but the hole is, at any rate 

 immediately after the emergence of the ant from the pupa, large 

 enough to admit a nearly full-grown larval Merniis which would 

 have been obliged to pass tlirough the minute aperture connecting 

 the thorax with the abdomen in order to take up its position in 

 the latter. The worm too would have been free in the nest previ- 

 ously, and, as has been seen, the worker ants kill an unprotected 

 worm. Other reasons also compel one to seek for another cause 

 for this aperture than the entrance of the worm, not the least of 

 which is the fact that a proportion of the infected ants were with- 



