26 
Psyche 
[ March 
backwards with equal facility. Sometimes it turns by re- 
versing- its head and gliding along its side. 
When the larva is full-grown, it advances to one extremity 
of the web and forms outside it a curious little mass of silken 
matter, so irregularly formed that it is scarcely entitled to 
be called a cocoon. The body is then shortened and the 
thoracic region is markedly thickened. The skin of the 
larva splits along the mid-dorsal line and the pupa draws 
itself forward leaving the old larval skin behind. If undis- 
turbed, the imago often remains quiescent for 3 to 4 days, 
but will rush out with amazing celerity at the slightest dis- 
turbance. 
Luminosity 
In a closely related species, Ceroplatus sesioides, Whal- 
berg (1848) was the first to state that the larva and pupa 
of Ceroplatus were luminous. Norris (1894) gave an ac- 
count of the luminosity of the New Zealand “glow worm.” 
He further suggested that the light emitted from the larva 
helped to attract small insects which the larva readily de- 
voured. 
Wheeler and Williams (1916) described the luminous or- 
gans in the New Zealand “glow worm,” Bolitophila lumi- 
nosa 1 as consisting of “the dilated tips of the four mal- 
pighian tubules which appear as four curved luminous rods 
and therefore constitute the photogenic organ.” Hudson 
(1926) stated that the light emitted was brighter on warm 
damp nights and brightest immediately before daybreak. 
In Macrocera and Ceroplatus which I reared in my bed- 
room, I carefully looked for luminosity in the larval and pu- 
pal stages of these insects, for several nights, and in no case 
was it seen. It is probable that the luminosity in the Eur- 
opean Ceroplatus sesioides recorded by Wahlberg was due 
to phosphorescent bacteria as is the case in certain chirono- 
mus larvae. 
x Dr. F. W. Edwards kindly sent me some larvae of the New Zea- 
land “glow worm.” From the morphology of the larva, it is clear to 
me that the larva is related to the European Ceroplatus and not Bo- 
litophila. Hudson later introduced the name Arachnocampa luminosa 
for the New Zealand “glow worm.” 
