(HAH. XXI. I 



BENEFICIAL INSECTS. 



203 



as being egg-parasites, that is to say, they hunt out ami oviposit 



in hatches of eggs laid by the insects which serve as their hosts- 

 A few insects of this group, which has not hern studied at all in 

 India as yet. arc known to be aquatic and to use their wings for 

 propelling themselves along under water. The unnamed and 

 undescribed species which we figure is parasitic on the 

 Tettigoniella spectra, a small white Jassid hug which is sometimes 

 very abundant in paddy-fields and which lays its eggs on paddy- 

 leaves which often become submerged in the water, and in this 

 case the parasite walks under-water in search of them. 

 parasites of this kind may be encourged, when egg-masses ot pests 

 are found, by placing these eggs in an open vessel surrounded with 

 oil-and-water, so that any flies which emerge may be able to fly 

 away whilst any caterpillars which hatch out will be unable to 

 escape. 



I ig. 90. Proctotrypid Parasite ■>! Tettigoniella spectra, ["he smaller 

 figure shows the natural si/r. (Original.l 



The Tachinidae, or Tachinid Flies, in general appearance much 

 resemble rather hairy house-tlies or flesh-flies and are parasitic 

 on caterpillars, grasshoppers, etc., on which the eggs are laid as a 



ride, the white maggots feeding inside their victim in much the 

 same way as ichneumonid grubs, but gem-rally killing it off iiist 

 .is it is full-grown, then emerging and changing on its collapsed 

 remains into characteristic small brown puparia, from which the 

 adtdt flies presently issue forth. 



The Bombylidse, which are usually hairy, bee-like two-winged 

 flies, extremely swift on the wing and often hovering stationary in 

 one place during flight, are parasitii on various insects, chiefly 

 Hvmenoptera. and several spec ies of these flies, which parasitize 



