Marshall. — On New Zealand Diptera. 227 



which a new generation developes. Sometimes as many as 

 five generations can be distinguished beneath the transparent 

 skin of a larva. 



3. Pupa. 



In the pupa nearly all the organs of the imago can be 

 distinguished — eyes, antennae, wings, legs, all being easily dis- 

 cernible. The insects appear to remain a very short time in 

 the pupa stage. 



4. Perfect Insect. 



Skuse states that, so far as his observations go, the insect 

 lives but a short time in the perfect state. With that con- 

 clusion the observations I have made on our New Zealand 

 species lead me to concur unreservedly. The insects are 

 particularly abundant in early spring, especially in the morn- 

 ings and evenings. They can be found in numbers in all dark 

 and shady places, many of them entering open windows that 

 face shrubberies and being easily caught on the glass panes. 

 Some species, however, can be found throughout the summer, 

 but the number of species commonly found in summer is very 

 much less than the numbers to be found in the spring. Their 

 flight is usually feeble, and is never in a direct line, the insect 

 darting hither and thither all the time it is on the wing. They 

 do not seem to fly any distance, but the wind is probably a 

 very important factor in their distribution. Mr. Skuse de- 

 scribes the extraordinary habits these insects have in New 

 South Wales of hanging in cobwebs and vibrating in such a 

 manner as to become more inconspicuous. Owing probably 

 to hasty observation, I have never found them in such situa- 

 tions. I deeply regret that I have hitherto been unable to 

 spare the time to investigate the life-history of any of the 

 native species of Cecidomi/idce. The larvae, as is well known, 

 are usually parasites on the foliage of flowering-plants. x-Vs a 

 result of the irritation produced by the larvae on the tissues of 

 the plant, monstrous growths, or galls, are produced. 



As regards the geographical distribution of these flies, it 

 may be said that species occur in every region of the globe 

 where the Diptera have been investigated. In Australia Mr. 

 Skuse has described ninety-five species, which he says repre- 

 sent in all probability but a very small proportion of the 

 total number of species present in that country. Up to the 

 present time no species have been described from New Zea- 

 land, but the present paper contains descriptions of twenty- 

 three species. As these have all been collected within twelve 

 months, the total number of species in the colony would pro- 

 bably be considerably over a hundred. These insects offer 

 many difliculties to the collector, for, in the first place, their 

 size is so minute that it is frequently a matter of no small 



