| Primary Vector Species in Massachusetts |
| Culiseta melanura feed primarily on avian species and are responsible for amplifying both EEE and WNV among the wild bird population. Culiseta melanura are multivoltine, meaning they have multiple generations throughout the warmer months. Climate plays a major role in how many generations Cs. melanura can produce each year. For instance, in southern states, Cs. melanura can produce three or more generations, whereas in Massachusetts, it can reach only two generations. However, this number may increase due to warming temperatures. Adult Cs. melanura and many other mosquito species will die off with the first hard frost (28°F for at least 2 hours), and the larvae will overwinter in what is referred to as “crypts,” found in red maple and white cedar swamps. |
| Culex pipiens play a significant role in the transmission cycle of WNV by amplifying the virus within the wild bird population. Similar to Cs. melanura mosquitoes, pipiens prefer avian hosts; however, they will also feed on mammals around dusk. Culex pipiens have multiple generations throughout the warm season, and an extended growth season with warmer temperatures in September will result in more generations. Once temperatures begin to cool, adult female Cx. pipiens will typically seek out man-made structures such as houses, sheds, and discarded tire piles to begin overwintering. Regarding habitat, pipiens prefer very stagnant water that can be found in catch basins, discarded tires, “green” swimming pools, and ditches around livestock animals. |
| There are additional species that play a role as bridge vectors in the virus transmission cycle such as Coquillettidia perturbans, Aedes vexans, Culex salnarius, and Ochlerotatus canadensis. Please see the Targeted Mosquito Species in the table below for more information regarding medical importance, habitat, and phenology. |
Targeted Vector Species in Pioneer Valley
| Species Name | Description | Habitat | Months Active |
| Aedes albopictus | An invasive species that is an aggressive and relentless day biter. Ae. albopictus prefer to feed on humans and can transmit chikungunya, dengue, and Zika. | Discarded tires and other containers. | June-October Peak: July |
| Aedes vexans | An aggressive biter that falls within the “flood water” species. Ae. vexans is a bridge vector for EEE and will feed on both birds and mammals. | Temporary freshwater pools such as flood meadows, retention ponds, and vernal pools. | May-October Peak: Varies and is dependent on precipitation. |
| Culiseta melanura | Cs. melanura mosquitoes are a primary vector for EEE. Cs. melanura feed mainly on avian species and are responsible for amplifying the virus to the point that it spills over into bridge vectors. | Tree root cavities or “crypts” covered by peat moss in red maple and cedar swamps. | May-December Peak: July-August and mid-September |
| Culex pipiens and restuans | These two mosquito species are abundant in Massachusetts and can amplify WNV in the bird population and infect humans. While Cx. pipiens is more implicated in WNV transmission, both Cx. pipiens and restuans are grouped together because differentiating between the two species with 100% reliability if very difficult. | Artificial containers such as “green” swimming pools, catch basins, discarded tires, buckets, etc. | May-October Peak: July-August |
| Coquillettidia perturbans | Cq. perturbans is one of the most abundant mosquitoes in Massachusetts and are considered a competent bridge vector for both EEE and WNV. Cq. pertubans will feed on both birds (reservoir for EEE) and mammals. | Permanent bodies of water with emergent vegetation such at cattails. | May-September Peak: July |
| Ochlerotatus canadensis | Oc. canadensis, is a bridge vector that can transmit both EEE and WNV to humans. | Woodland/vernal pools. | May-October Peak: June |
| Ochlerotatus japonicus | An invasive species that is a potential bridge vector for WNV and EEE. | Discarded tires and other containers | May-October |
| Culex salinarius | Cx. salinarius are considered bridge vectors for both EEE and WNV, readily feeding on mammals. | Brackish and freshwater swamps. | May-November Peak: August |
| Other species | There are many other species that PVMCD staff will submit to the Arbovirus Surveillance Laboratory at DPH for testing. These species are considered potential vectors in transmitting arboviruses. |
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