S3 
On cucumbers and muskmelons, from May to September, 1882. 
LIFE HISTORY. 
There is yet very much work to do on the life histories of the 
plant-lice, especially upon the subject of their fall and winter 
history. A few are known to hibernate as mature insects—the 
apple Aphis, for example — but most of the small number which 
have been followed through the year, lay their eggs in autumn and 
perish. The plant-lice hatching from these eggs are all wingless 
females, as far as known. With respect to the cucumber Aphis, 
there is no more certainty on this point than in any of the other 
species. I searched carefully for eggs and living plant-lice after the 
usual time of oviposition, but was unable to find either. This was 
doubtless due to the fact that the plant-lice in all the fields under 
our observation were almost completely exterminated by their para¬ 
sites, long before the vines were killed by frost. An hour’s search 
in September, in one of the fields that had been worst infested, dis¬ 
covered less than a score of living plant-lice at that time, although 
hundreds and thousands of their parasitized bodies still remained 
clinging to the leaves. If their eggs were left in these fields, they 
were of course far too few to be found by an indiscriminate search. 
I have but a single fact bearing in any way upon their winter his¬ 
tory. Several observations made at Normal and elsewhere, indicate 
that fields which had been in cucumbers or some similar crop dur¬ 
ing the preceding year, were much the most generally and injuri¬ 
ously affected by this plant-louse. If this should prove to be the 
common rule, it would be fair to infer that the insect spends the 
winter upon the ground where it developed, either as adult or in 
the egg. Reference has already been made to the occurrence of a 
form upon the roots. This I saw only late in the season in one of 
the worst infested fields, where I made a thorough and protracted 
search with a view to determining whether the species had a root- 
form or not. Not over half a dozen specimens were found at that 
time, but these were unmistakably of the same species as those 
which occurred upon the leaves. From the general appearance of 
the roots of the infected plants, it is not impossible that much of 
the injury noticed was done earlier by the root-lice—perhaps more 
than by those appearing upon the foliage. 
INJURIES TO VEGETATION. 
The evidences of the injury done by these lice were of the usual 
kind. The leaves were curled and crumpled, with an unhealthy 
hue, and were much smaller than those not troubled by lice, and 
the entire plant was stunted, and evidently rendered thoroughly un¬ 
healthy. The roots were crooked and knotty, and destitute to a 
great extent of fibrous rootlets. After the disappearance of the lice 
in August, the affected plants recovered but slowly, although most 
finally put out new foliage, and yielded a part of a crop. 
