A line of dolls resembling vampires is sucking the blood out of Barbie sales from toy stores around the country, the Christian Science Monitor reported.

Mattel’s Monster High dolls, also known as “Goth Barbies,” have been a huge hit for the country’s largest toy manufacturer since their debut in 2010.  They are based on teen characters that are offspring of famous monsters.

According to the Monitor, Mattel reported Wednesday its second quarter net income fell by 24 percent, largely in part due to the lack of Barbie sales, along with a $14 million write-down on the toy maker's Polly Pocket line. The company’s shares dropped 7 percent as a result.

This marks the fourth straight quarter in which Barbie sales have slipped.

But while sales of Barbie dolls have set like the sun on a Malibu beach house, BMO Capital Markets analyst Gerrick Johnson estimates sales of the Monster High dolls have likely grown to more than $500 million in just three years since the line debuted.

Still, the dolls’ monster success has been overshadowed by a continued slide in Barbie sales, a drop the Goth-inspired cuties are partly responsible for.  "We've introduced new franchises that have fueled significant category growth for the industry," Mattel CEO Bryan Stockton told the Monitor.  "The Barbie brand is likely being modestly impacted by their successes."

Stockton pointed out that Barbie sales are higher than when the Monster High dolls were introduced in 2010, and that Barbie continues to be the largest doll brand.

Stockton also noted that Barbie sales will likely pick up in the second half of the year, as new shipments of products increase with the approaching holiday season. Mattel refers to this time as “the season,” while the other three quarters are known as the “preseason.”

However, Barbie sales have slipped 12 percent in the latest quarter, while sales of the company's other girls brands rose 23 percent. This difference can be attributed largely to the increasing popularity of the Monster High dolls.

Mattel did not respond to a request for comment from FoxNews.com.

According to the Christian Science Monitor, the toy industry has witnessed a small decline this year for other reasons, as well. Cautious consumer spending, an increase in demand for smartphones and tablets, and a drop in sales in the video game industry have also hurt Mattel, along with other toy stores.

For the April to June quarter, Mattel’s net income was $73.3 million with shares of 21 cents.  This marks a drop from the same quarter of the previous year, when net income was $96.2 million with shares of 28 cents.

Click for more from The Christian Science Monitor.