Aleochara bilineata is known both as a parasitoid and a predator when it comes to North American crops and farmland (Royer and Boivin 1999). The species of Delia radicum known commonly as cabbage maggots are one of the natural herbivore predators of brassicaceous crops (crops related to the cabbage family). The D. radicum females lay their eggs at the base of the plant so that when the larvae mature they tunnel through the taproots and feed on the vascular tissues of the plant (Broatch et al. 2008). Once the vascular tissues of the plant are damagedImage of two white Delia radicum maggots and one brown maggot, the plant cannot transport its water and nutrients causing damage or death. This loss of crops causes a deficit of millions of dollars annually to farmers (Broatch et al. 2008).This is where A. bilineata factor in.

As a natural parasite and predator of the D. radicum (cabbage maggot), A. bilineata serves as a biological control agent for these crops. By parasitism and predation on the maggot, A. bilineata controls the population and therefore diminishes the loss of crops for farmers (Royer and Boivin 1999). A. bilineata is a predator to both the eggs and larvae form of the D. radicum. A single adult beetle is capable of consuming an average of 23.8 eggs or 2.6 larvae per day. It was further concluded that under optimum conditions a single pair of A. bilineata adults could destroy about 1,210 eggs and 128 larvae in their lifetimes (Broatch et al. 2008). Not only do the adult beetles destroy the young maggots but they also parasitize on the pupae.

The pupae stage occurs when the insect is inactive in between the larvae and adult stage (Webster Dictionary 2013).  On average, each female of A. bilineata can produce 9-to-15 eggs per day or 700 eggs in its lifetime. When the larvae of A. bilineata hatch in under a week, they locate D. radicum pupae. Once the A. bilineata larvae reach the pupae they proceed to chew a hole in the wall of the puparium and then eventually consume the developing maggot pupa inside (Broatch et al. 2008). A pupariuadult Rove Beetles attacking a fly maggotm is defined as the last hardened larval skin that encloses the pupa (Webster Dictionary 2013). Once the A. bilineata has completed this process, it overwinters and emerges out of the puparium in the spring as a full beetle adult (Broatch et al. 2008).

This process is a unique form of parasitism because the larvae of the beetle are solely responsible for locating and inhabiting the host pupa. Essentially, the mothers of the larvae have no influence in the success or fitness of its offspring because they do not select or evaluate the suitability of the host (Balog et al. 2008). The parasitism process is able to occur because the larvae are able to distinguish between parasitized and non-parasitized hosts. This ability is very unique to the Aleochara species and has never before been described in a coleopteran (winged-insect) parasitoid of this nature (Balog et al. 2008).

This parasitoid relationship, along with the previously mention predation relationship, is essential to farmers’ crops and was found to be up to 94% effective in some Canadian territories (Broatch et al. 2008). Therefore, it can be concluded that there is a mutualistic relationship between the A. bilineata and the cabbage crops. This is because the beetle provides protection for the plant, and the plant is the home to the prey of the beetle. This interspecies relationship is only one example of the A. bilineata’s interactions with other organisms; however this is the most studied relationship and has the most prominence to our human culture and way of life.

Check out our reference page for more information on our facts and sources!

For more information on this interaction, visit our Reproduction page.
Return home