The carp (Cyprinus carpio) and goldfish (Carassius auratus) were found to be of special value in the ponds and fountain-basin in and about Auckland. They eat the eggs, larvae, and adult mosquitoes.

Every garden pool should be provided with carp or goldfish.

The active little native bully (Gobiomorphus gobioides) feeds eagerly on mosquito larvae, and as it is common in small creeks and ponds, no doubt helps to keep the number of mosquitoes in check. At Bethell's, on the West Coast, a lake well-stocked with G. gobioides was quite free from mosquito larvae, as were several creeks at Rawene (Hokianga) where the “bully” was abundant. At Herekino, a barrel of Water swarming with eggs, larvae and pupae was completely cleared within a day by the introduction of a few “bullies.”

The top minnow (Gambusia affinis) is a native of the United-States and inhabits shallow and sluggish waters. Its value in the-control of mosquitoes has been established in many parts of the-world.

In 1928, Dr. T. W. Hughes, Medical Officer of Health for Auckland, obtained 43 specimens from Hawaii for experimental purposes. Within 10 days they commenced to die, and in spite of changes of water and every care they were all dead in three weeks.

In the United States these fish require a good deal of attention and thrive only in suitable waters and conditions, and even if established in New Zealand, would have to compete with our native Galaxiads find bullies. The most likely places in which they might be of service are the large areas of shallow swamp waters.

The “water-bug” (Anisops assimilis) and the “water-beetle” (Rhanthus pulverulosus) which are common in ponds, troughs and tanks, are very vigorous natural enemies of mosquito larvae.

Experiments showed that Anisops assimilis takes the larvae-greedily, but will attack the pupae only when larvae are absent, and even then slowly and reluctantly. Field observations also have shown that in pools or troughs stocked with Anisops assimilis the larvae-do not even reach the pupal stage: indeed, very few reach the third instar. A field observation, frequently made, shows that although water troughs for horses and cattle usually contain “water-bugs” which keep them free from mosquito larvae, the puddles made beside them by the visiting animals' feet are not permanent enough to maintain this control. Nevertheless, these pools last long enough to permit a mosquito brood to come to maturity, and we here get the significant occurrence of larvae in a temporary puddle and their absence from a permanent water-container, the latter, however, containing an energetic mosquito enemy. These conditions apply chiefly to troughs in country towns, those in public thoroughfares in larger-towns being usually without predatory insects and therefore requiring to be emptied once in 10 to 14 days.

The aquatic larva of the beetle Rhanthus pulverulosus, which inhabits a variety of ponds, pools and artificial containers, also attacks the mosquito larvae by sucking out the body contents, audit was observed that four R. pulverulosus larvae could, between them, devour 100 mosquito larvae within two days.