Watt. — Study of New Zealand Entomology. 255 



Periods. 



Period of incubation, seven days ; weather hot. 1st stadium: March 27 

 to April 1, five days; length, ^ in. ; mild. 2nd stadium: April 2-6, 

 five days ; length, -^ in. ; mild. 3rd stadium : April 7-12, six davs ; 

 length, -^ in. ; colder. 4th stadium : April 13-17, five days ; length, 

 ■^ in. ; mild. 5th stadium : April 18-22, five days ; length, f in. ; mild. 

 6th stadium: April 23 to May 4, twelve days; length, 1-1 J- in. ; cold. 

 Duration of pupal stage, eighty-five days ; cold weather. 



Notice the comparatively equal duration of the stadiums, and the in- 

 fluence of the weather upon these. As mentioned in a former paragraph, 

 temperature may be the cause of lengthening or shortening these periods, 

 or even of increasing the normal number of stadiums. By separating one 

 batch into two lots, and treating one of the lots to artificial temperature 

 a few degrees higher than that prevailing in the open, the 3rd stadium was 

 shortened from five to two days only. 



Food Plants. 

 Solatium aviculare. S. nigrum. These were, in all probability, the 

 original food plants, but the larvae have now taken almost exclusively 

 to introduced plants, and are in consequence becoming a dangerous pest 

 to the flower-gardener. The larvae are now seldom found on S. aviculire, 

 and then only in parts where introduced plants are still scarce ; they still, 

 however, favour S. nigrum even in richly cultivated districts. The follow- 

 ing introduced plants are eagerly eaten : Dahlia, salvia, geranium, potato, 

 tomato, nettle (introduced), beans, Scotch thistle, mint, horseradish. 



Parasites. 

 # The larva is often attacked by a small Hymenopteron belonging to the 

 family Braconidae. These parasites, to the number of thirty or more, 

 emerge from their host just prior to its pupating, and spin their small cream- 

 coloured cocoons on the leaves of the plant on which the host has been 

 feeding. The victim. may be found later lying upon the ground, its sides 

 scarred by large open circular black-edged wounds from which parasitic 

 larvae have emerged. Prior some days to the exit of the parasites the larva 

 becomes very torpid, moving but little, and eating nothing ; externallv 

 nothing appears to be the matter with it. The cocoons of the parasite are 

 short, cylindrical, and very flufl'y, and are collected in small heaps upon 

 the leaves. One unacquainted with the life-history of these little creatures 

 would often be puzzled to account for the presence of small masses of the 

 cocoons on the leaves of many garden plants. The duration of the pupal 

 existence is about forty-six days. At present this Hymenopteron is 

 unidentified. 



The Cocoon. 



The favourite situation for the cocoon is between two or more leaves 

 some little distance from the ground. The silk is white and strong, and 

 the cocoon rather fluffy externally, and is never so thick but what the en- 

 closed pupa can be easily distinguished. It often happens that the larvae 

 will forsake their food plant to spin in vegetation yards away. The con- 

 struction occupies from two to three days. 



The Pupa. 

 At first the pupa is considerably active if disturbed, twirling its abdo- 

 men with a circular motion ; later, however, it becomes much less active. 



