Large Milkweed Bug Colony 2021
This colony of Large Milkweed Bugs (Oncopeltus fasciatus) was observed July 18 - August 19, 2021 on Butterfly Weed (Asclepias tuberosa). An adult was first seen on the plant on July 18. I thought it was just visiting and did not think to look for eggs. When I looked at the plant again on July 29, there were second (L2) and third (L3) instar larvae present. Below is a timeline of the larval stages observed:
Adult-- July 18
L2 larvae -- July 29
L2 & L3 larvae -- August 2 and August 4
L4 larvae start to emerge --August 5
L5 larvae start to emerge -- August 9
Adults start to emerge -- August 15
Most adults gone from the plant -- August 19
Assuming that the adult laid eggs on July 18, there were 12 days between egg-laying and the next observation of L2 larvae. This timeline is consistent with Niswander (1951) who reported that eggs hatch in five days and the L1 stage averages 4-6 days. The time between one larval stage and the emergence of the next stage in my observations are as follows:
L2 -- greater than or equal to 4 days
L3 -- 5 days
L4 -- 7 days
L5 -- 5 days
Adults stay on original plant -- 4 days
These times are mostly consistent with Niswander, except the L5 stage which is shorter than reported. All of these times are shorter than those reported by Sauer and Feir (1973). These discrepancies can be accounted for by differences in location, temperature, relative humidity, and counting method used to record beginning of each subsequent larval stage.
The bugs were found primarily on the milkweed pod where the initial adult was observed. By the L4 and L5 stages, they had moved to another adjacent pod and were venturing onto the leaves and stems. The mature adults were seen walking to the ends of leaves, spreading their wings and flying away.
After August 19, all but one of the bugs had left the plant and the remaining individual was still in the L4 stage. I could not find this individual after August 19 and do not know if it completed its lifecycle.
References:
Niswander, R. 1951. Life history and respiration in the milkeed bug Oncopeltus fasciatus (Dallas). Ohio J. of Science 51:27-33.
Sauer, D. and D. Feir. 1973. Studies on natural populations of Oncopeltus fasciatus (Dallas), the large milkweed bug. American Midland Naturalist, pp.13-37.
