206 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
Number 
Frequency 
Number 
Frequency 
Number 
Frequency 
48 
3 
53 
2 
60 
1 
49 
2 
54 
1 
67 
1 
50 
1 
55 
1 
68 
2 
51 
2 
56 
1 
70 
1 
52 
3 
59 
2 
71 
1 
The eggs are creamy white when first laid, becoming yellower in a 
few hours, orange in a couple of days, and when nearly ready to hatch 
the dark brown head of the young caterpillar can be seen through the 
transparent shell. The clusters parasitized by Trichogramma become 
black soon after parasitization, and after the emergence of the parasite 
the eggs are still black because of the black debris remaining; while of 
the unparasitized eggs only a whitish egg shell is left when the cater¬ 
pillar hatches out. It is thus possible to tell definitely, except when 
freshly parasitized, which clusters and which eggs in the cluster are 
parasitized. Of 380 clusters on which data are available, 65.3 per cent 
were totally parasitized and 34.7 per cent only partly parasitized, 20 
per cent of the eggs in these clusters being not parasitized. 
The egg-masses are impartially deposited on either the upper or 
lower side of the cane leaves. They may be on the midrib or on any 
other part of the leaf, even to the edge, but usually they occur from 
the center to the tip, rather than closer to the stem of the plant. In 
collecting Diatrcea egg clusters a portion of the leaf surrounding the 
egg-mass was broken off and placed in a tin box. All collections were 
made between the hours of 7 a. m. and 10 a. m. In the afternoon the 
bits of leaves bearing the egg-masses were removed from the tin boxes 
one by one and trimmed so as to go easily into a 7 mm. x 25 mm. vial. 
Corks were used to close the vials after they had been allowed to dry 
out for half an hour or more, and a wad of absorbent cotton was 
packed down in the bottom of the vial on the opposite side of the piece 
of leaf from that bearing the eggs. In this way the moisture exuded 
and transpired was largely eliminated and the piece of leaf was held 
securely in place. Unless the cotton was tightly packed in, however, 
the emerging caterpillars, and especially the adult Trichogramma y 
became inextricably entangled in the loose fibres. Both young Dia¬ 
trcea caterpillars and adult Trichogramma are positively phototropic 
to a very marked degree, and when the bottom of the vial was towards 
the window, they would push into even the most tightly wadded piece 
of cotton in their efforts to reach the source of light. When the vials 
have the corks towards the window, some of the Trichogramma manage 
to get between the cork and the edge of the vial, and are often crushed 
when the cork is removed, while the young Diatrcea caterpillars will 
bore into the dry cork, often making a tunnel several times their own 
length. To obviate the difficulties connected with the phototropic 
