Total mosquito counts varied from year to year (Fig. 2A). Once mosquitoes were collected, they were identified by species. Trends are seen in the yearly count of mosquitoes, when accounting for the different mosquito species that were found in the county each year. See Suppl. material 2 for a table of total mosquitoes collected per species per year. Each year, the Aedes genera of mosquitoes consistently record the most number of mosquitoes collected. The Culex genera represents the next genus of mosquitoes with a high abundance throughout the year. Additionally, the Psorophora genus of mosquitoes have had consistently lower proportions of collected mosquitoes.

Figure 2.  

(A) Total number of mosquitoes collected and number of trap collections each year, from 1976 to 1997; (B) total number of collections each year, from 1976 to 1997. Mosquito abundance totalled for all species collected each year during the collection period shows large variation in the number of mosquitoes collected each year. Note: some variation is due to differences in trapping effort as well as collections removed because we could not determine their historical placement location. The side-by-side comparison of these graphs allows some observations to be made and evaluated regarding the explanation behind trends that were found in the data.

As total mosquito counts for each year is a partial reflection of the number of trapping sites and collections (i.e. collection effort), implications about species distribution can be better understood when looking at each collection year separately. The number of active traps remained relatively similar throughout the data collection period and ranged between 11 traps and 16 traps where the location could be determined. However, the number of unique collections did change greatly throughout the collection period which must be taken into account when looking at year-to-year differences in the abundance of various mosquito species. In 1976, 44 collections were reported; while 672 collections were reported in 1996. The unique collection count for each year is depicted in Fig. 2B.

The newly-created dataset will facilitate future research endeavours, which have the ability to be impactful in various fields of biological sciences, such as a number of studies (van Klink et al. 2020, Arora et al. 2022, Campbell et al. 2022) that performed novel analysis using historical mosquito surveillance records accessed on VectorBase (Giraldo-Calderón et al. 2022). We highlight in Fig. 3 that the dataset can be used to explore phenology/seasonality over several years.

Figure 3.  

Seasonality of mosquito species can be detected in the dataset. (A) The daily collections numbers of a single mosquito species, Ae. vexans, collected over 5 years; (B) Mosquito collections, by week, averaged across the entire multi-year dataset and binned by genus. Ae. vexans, the most dominant species collected, has been removed. Noticeable differences in seasonal patterns by genus are evident.

The compiled dataset will be especially important for the consideration of various diseases that are most commonly spread by infected mosquitoes. One of these viruses, WNV, is spread by infected mosquitoes and was first detected in Indiana in 2001 (Indiana State Department of Health 2018). In 2018, the Indiana Annual Report of Infectious Diseases reported 35 cases of WNV with four deaths. Fig. 4 presents the yearly abundance for four mosquito species known to be carriers of WNV. These mosquito species include members of the Culex pipiens morphological group, Culex tarsalis, Aedes vexans and Aedes triseriatus.

Figure 4.  

Yearly abundance for four WNV vector species. All four species are known to be carriers of West Nile Virus: (A) Culex pipiens morphological group; (B) Culex tarsalis; (C) Aedes vexans; (D) Aedes triseriatus. These species represent some of the most abundant species in St. Joseph County throughout the data collection period (1976 to 1997).

The Indiana Department of Health reports Eastern Equine Encephalitis Virus (EEE) to be “the most dangerous mosquito-borne virus that is naturally present in the state of Indiana” (Indiana Department of Health 2023). Thus, it is important to recognise three species found in St. Joseph County as known carriers of EEE (Fig. 5). These species include Culiseta melanura, Coquillettidia pertubans and Aedes canadensis. While both Culiseta melanura and Aedes canadensis had relatively low counts throughout the collection period, they both have peaks in various years. It is important to recognise that Coquillettidia pertubans have had a trend of increased abundance throughout the entire collection, which may be important regarding the reports of EEE in Indiana.

Figure 5.  

Yearly abundance for three EEE vector species. All three species are known to be carriers of Eastern Equine Encephalitis Virus (EEE): (А) Culiseta melanura; (B) Coquillettidia pertubans; (C) Aedes canadensis. The number of collections of Cq. pertubans had a noticeable increase from 1976 to 1997.

This reported dataset is included here as a MIReAD-compatible (Rund et al. 2019) supplemental file (Suppl. material 1). It will also be deposited in the VecDyn database at www.VectorByte.org.

This report is based on historical species records and not samples and, thus, voucher specimens are not available. The original collections were made as part of regular disease surveillance efforts in our county from species known to be present. We note some physical specimens from the area and time period were deposited in the Notre Dame Biodiversity Museum, but these were not examined as part of this work. We refer readers to a work published closer to the time of the original data generation from authors in our area (Young et al. 2008) for further information on local Indiana species occurrence.