﻿long and some of them, especially a species of Alaptiis that I 

 liave studied, can run with astonishing rapidity. 



Even though they be unacquainted with the Mymaridae them- 

 selves, most entomologists know that the family contains most 

 of the very few parasitic Hymenoptera that are known to enter 

 the water of their own accord. Some of these species swim by 

 means of their wings, others of their legs, and they are parasi- 

 tic in the eggs of insects that are wholly or partly aquatic, such 

 as dragon-flies,* water-bugs and water-beetles. 



During the past six months I have bred many thousands of 

 several species of those Mymaridae, that are parasitic in the 

 eggs of leaf-hoppers, in order to distribute them to the diiTerent 

 sugar plantations troubled with the pest. Consequently I have 

 had many opportunities of observing their habits, which while 

 alike in most respects, yet differ somewhat in detail. 



GENERAL ACCOUNT OE PARANAGRUS OPTABILIS. 



Though not one of the smallest, since it measures about ^ 

 mm. this species is of very slender and delicate form, and has 

 long fringes to both front and hind wings. It has that habit 

 of rising slowly upwards on the wing, often with more or less 

 spiral flight, that I have already alluded to. In captivity it is 

 quite easily seen as it runs actively about on the leaves of the 

 cane plants continually touching their surface with' the tip of its 

 antennae. On arriving at a fresh scar, marking the place 

 where a leaf-hopper has laid its eggs, it thoroughly investigates 

 tliis with the characteristic dilated club-joint of the antennae. 

 After this investigation it sometimes passes on, but at others 

 it proceeds to thrust the tip of the ovipositor into the egg cham- 

 ber of the leaf-hopper, still keeping the tips of the antennae in 

 touch with the surface. (PI. XIII fig. ^.) Since the antennae 

 are directed vertically (or nearly so) downwards, and are re- 

 latively of great length, in order to bring their tips in contact 

 with the surface of the leaf the parasite is obliged to raise itself 

 high on its two front pair of legs, and consequently assumes a 

 characteristic position during oviposition. The ovipositor, 

 when freed from its sheaths and in action, forms a strong angle 

 with the lower surface of the abdomen, in some cases approach- 

 ing a right angle. When the scar, that marks an egg-chamber, 

 is after investigation passed by, though it is evidently recent, 



* 111 these remarks the seiius Piesti.'ichia is iiu-ludecl, since it has generally been 

 assigned to the Mymaridae (but erroneously) aud its habits have been specially studied. 



