BLOWFLIES

Press, Volume LXX, Issue 21147, 24 April 1934, Page 7

BLOWFLIES

I TO TUE EDITOR OP THE I'HF.SS. | Sir,—ln reply to the letter by "Ampersand" asking for information on the phrase, "There are two kinds [of blowflies in New Zealand], one laying eggs and the other bringing forth its young in a living state," the following may be of interest. There are at least 16 species of blowflies in New Zealand, four of these are native, five are Australian, and seven are of European origin but world-wide in their distribution. In that comprehensive report, "The Sheep Blowfly Problem in Australia," by the Joint Blowfly Committee, published in January, 1933, it is stated that certain species of blowflies never lay eggs, but deposit young, active maggots. In Australia these are the lesser brown blowfly (Calliphora augur) and some of the striped blowflies of the genus Sarcophaga. Now it is the accepted belief in New ; Zealand that the introduced Austra- ' lian blowfly Calliphora (Pollenia) ! stygia lays eggs in mild seasons and ['living maggots in hot weather. The I above-mentioned report does not supI port this belief, which was at one I time held to be true of this fly under Australian conditions. Hence there is some doubt whether blowflies lay living maggots in New Zealand. Of course, it is well known that a certain number of insects produce larvae instead of laying eggs, and are then said to be viviparous. Viviparity is due to the fact that the eggs are retained within the body until the end of embryonic life and i.he contained insect has emerged. It is found in scattered instances among earwigs, mayflies, moths, and beetles: in greenflies and a number of two-wmgec> flies it is a regular feature. In the case of the Tsetse fly and the sheep "ked" or "tick" only a small number

| of eggs are produced, and each mag- | got passes its life in the uterus of the female, where it is nourished by a special secretion. After extrusion it is changed almost immediately into a pupa, from which the adult emerge* in due course.—Yours, etc., L. MORRISON. April 23, 1934.