276 The Philippine Journal of Science i9i8 



BIOLOGICAL NOTES ON PACHYRRHYNCHUS VENUSTUS 



WATERHOUSE 



For a number of years, whenever collecting Pachyrrhynchus, 

 I have endeavored to discover the immature stages of the various 

 species, as well as their food plants and individual habits. To 

 my knowledge there have been no published records on the 

 biology of any species of this genus. As a rule, most species of 

 the Pachyrrhynchus-Apocyrtus groups are found congregated 

 in one locality, sometimes in large numbers on their supposed 

 food plants. Since all of the species of the above groups are 

 wingless forms and are, therefore, unable to fly, it seems rather 

 strange that their breeding habits should be so difficult to 

 discover. My efforts to discover something of the life histories 

 of P. congestus Pasc, P. modestior Behr., and P. pinorum Pasc, 

 which are rather common around Baguio, failed entirely; with 

 P. venustus I was more successful. This species is found at 

 the fresh-water swamp near Los Baiios, the latter being an 

 extension of the large lake, Laguna de Bay. This swamp con- 

 tains no large trees, but a mass of shrubs, bushes, and a heavy 

 growth of a peculiar fern.' The water in the swamp varies in 

 depth from a few centimeters to a half meter or more at certain 

 times. Since I had found most of the P. venustus climbing 

 about on this fern, I examined this plant very closely. By cut- 

 ting the leaves and the old leaf axils and splitting the trunk, or 

 caudex, I finally located the larvae and one pupa. The larvae 

 are found in the older, lower part of the trunk, which consists 

 of alternating soft and very hard tissues. The larvae feed in the 

 soft parts, their channels being very short. The larvae are 

 oblong and of uniform diameter. The pupa was located in a 



' Prof. E. D. Merrill kindly determined this fern and furnished the fol- 

 lowing description: 

 Acrostichum aureum Linnaeus. 



A very coarse tufted fern from thick suberect root-stocks, which often 

 form a distinct caudex. Fronds large, simply pinnate, 50 to 200 centi- 

 meters long, the pinnas oblong, coriaceous, entire, 20 to 50 centimeters 

 long, 4 to 6 centimeters wide, somewhat stipitate, glabrous, apex obtuse to 

 retuse, sometimes mucronate, the midribs stout, the veinlets distinct, 

 freely anastomosing. The upper pinnse are fertile, wholly or in part, the 

 sporangia densely covering the entire back of the pinnse or parts of them. 



In brackish swamps throughout the Philippines, occurring also about 

 mineral springs inland, such as those at Los Banos, and at Daklan, Ben- 

 guet Subprovince. Near the seashore in all or most tropical countries. 

 Tagalog name, lagolo. 



