October, ’23] 
cutright: micromus life history 
451 
Table I.—Length in days of Egg Stage, Larval Instars, and Pupal Period of Micromus 
posticus Walker 
Larva number. 
bfl 
W 
1st Instar 
2nd Instar 
3rd Instar ac¬ 
tive 
and 
Pre pupal 
period 
Pupa 
Larval stage 
Egg to adult 
Preoviposition 
period 
Egg to egg 
1. 
4 
2 
1 
2 
2 
5 
7 
16 
2. 
4 
2 
1 
2 
2 
5 
7 
16 
3. 
4 
2 
1 
2 
2 
4 
7 
15 
4. 
4 
2 
2 
2 
2 
5 
8 
17 
5. 
4 
2 
2 
2 
3 
4 
9 
17 
3 days 
20 
6. 
4 
2 
2 
2 
3 
4 
9 
17 
7. 
4 
3 
1 
1 
3 
5 
8 
17 
8. 
4 
2 
2 
1 
3 
5 
8 
17 
9. 
4 
2 
2 
1 
3 
5 
8 
17 
10. 
4 
3 
2 
1 
3 
5 
9 
18 
11. 
4 
3 
1 
2 
3 
3 
9 
16 
12. 
4 
3 
1 
2 
3 
3 
9 
16 
13. 
4 
3 
1 
2 
2 
4 
8 
16 
4 “ 
20 
14. 
4 
2 
2 
2 
2 
4 
8 
17 
15. 
4 
4 
1 
2 
2 
4 
9 
17 
3 “ 
20 
16. 
4 
3 
1 
2 
2 
4 
8 
16 
Totals 
64 
40 
23 
68 
64 
131 
Avera ges 
4 
2 K 
IK 
4K 
4 
8 + 
Table II constitutes the feeding record of the sixteen larvae from which 
the data were obtained for Table I. Figures at the top of each daily 
square show the number of aphids available as food and those at the 
bottom give the number destroyed. (See next page) 
The following tabular summary of Table II is given showing the aver¬ 
age, the maximum, and the minimum number of aphids eaten in each 
stage. 
Ave. 
Max. 
Min, 
First Instar. 
. 10 
16 
4 
Second “ . 
. 11 
21 
3 
Third “ . 
. 20 
28 
3 
Total period. 
. 40 
56 
27 
The averages show that feeding is about the same in the first two in¬ 
stars and that the third practically doubles these two in amount of food 
consumed. The small amount of food used is especially noticeable when 
it is compared with the larval feeding records of the Coccinellids, where 
averages of from one hundied to six hundred aphids destroyed are not 
uncommon. 
After the third instar has progressed several days (see Table I) the 
larva spins a very loose meshed almost circular cocoon which will measure 
from seven to eight mm. in diameter. This will correspond roughly to 
the length of the larva, as it is spun without curling up. We now have a 
structure somewhat resembling two saucers placed together, concave 
surfaces joining with the larva inside. This outer cocoon is really a 
